Maturation of the head of bacteriophage T4. I. DNA packaging events.

Summary This paper describes the histogenesis of 3 forms of human malignant melanoma: superficial spreading melanoma, nodular melanoma, and lentigo maligna melanoma. A comparative analysis by computer of the biologic behavior and clinical characteristics of the different neoplasms has been done. An additional 60 tumors have been studied by serial block sectioning. Evidence is presented suggesting that superficial spreading melanoma and lentigo maligna melanoma (Hutchinson9s melanotic freckle), though evolving at different rates, show a long period of superficial growth, followed by the relatively rapid appearance of nodules or deeper invasion within the primary lesion. This change in the nature of the primary lesion may be due to the appearance of one or more strains of cells of aggressive biologic potential. Thus the primary melanoma may exist for a relatively long period of time during which host selectional forces act to permit the growth of quite malignant strains of cells. It is these cells that seem to be capable of deeper growth. The subdivision of each of the forms of melanoma into 5 anatomic levels of invasion permits the accurate assignment of prognosis to each case. It is suggested that melanomas are tumors of the epidermal melanocytes and are not necessarily derived from melanocytic nevi. Each melanoma has a distinctive clinical appearance, even in its superficial and curable phases, and this appearance is the same whether or not the process arose in association with a melanocytic nevus.

https://cancerres.aacrjournals.org/content/canres/29/3/705.full.pdf

The Histogenesis and Biologic Behavior of Primary Human Malignant Melanomas of the Skin

The transendothelial passage of horseradish peroxidase, injected intravenously into mice, was studied at the ultrastructural level in capillaries of cardiac and skeletal muscle. Peroxidase appeared to permeate endothelial intercellular clefts and cell junctions. Abnormal peroxidase-induced vascular leakage was excluded. Neutral lanthanum tracer gave similar results. The endothelial cell junctions were considered to be maculae occludentes, with gaps of about 40 A in width between the maculae, rather than zonulae occludentes. Some observations in favor of concurrent vesicular transport of peroxidase were also made. It is concluded that the endothelial cell junctions are most likely to be the morphological equivalent of the small pore system proposed by physiologists for the passage of small, lipid-insoluble molecules across the endothelium.

/pdf/the-ultrastructural-basis-of-capillary-permeability-studied-5dsina2wex.pdf

The ultrastructural basis of capillary permeability studied with peroxidase as a tracer

Maturation of the head of bacteriophage T4. II. Head-related, aberrant tau-particles.

The nucleoids of Escherichia coli, independently of the physiological state of the bacteria, are shown to be preserved as a fine-stranded fibrillar nucleoplasm by an OsO(4) fixation under defined conditions: acetate-veronal buffer pH 6, presence of Ca(++) and amino acids, stabilization with uranyl-acetate before dehydration. The same fixation procedure applied to the DNA of vegetative phage reveals a pool of homogeneous fibrillar structure very similar to the nucleoplasm. The "versene test," which produces a coarse coagulation of these plasms, emphasizes the similar behaviour of the pool and the nucleoids. The heads of mature phage are preserved in their true polyhedral shape by the standard fixation procedure, although they may be badly distorted when fixed under different conditions. Lanthanum nitrate and uranyl-acetate are shown to increase markedly the contrast of both phage and cytoplasm. The consequences of the fibrillar structure of the genetic material are discussed in relation to the probable division process.

/pdf/electron-microscope-study-of-dna-containing-plasms-ii-2o2yw7uon4.pdf

Electron microscope study of DNA-containing plasms. II. Vegetative and mature phage DNA as compared with normal bacterial nucleoids in different physiological states.

Electron microscopical studies of phage multiplication. IV. The establishment of the DNA pool of vegetative phage and the maturation of phage particles.

Janine Séchaud

Papers

Electron microscope study of DNA-containing plasms. II. Vegetative and mature phage DNA as compared with normal bacterial nucleoids in different physiological states.

Electron microscopical studies of phage multiplication. IV. The establishment of the DNA pool of vegetative phage and the maturation of phage particles.

Functions and properties related to the tail fibers of bacteriophage t4.

Electron microscopical studies of phage multiplication. II. Production of phage-related structures during multiplication of phages T2 and T4.

On the fragility of phage T4-related particles.