J. A. Serra

Bio: J. A. Serra is an academic researcher from University of Coimbra. The author has contributed to research in topics: Position effect & Dominance (genetics). The author has an hindex of 3, co-authored 8 publications receiving 57 citations.

Constitution of Hair Melanins

Abstract: MELANINS can be extracted from hair by dilute caustic soda solution and purified by chromatography on calcium and magnesium carbonates1,2. The extraction with 0.05 N caustic soda is easier with rabbit hair and sheep wool than with human head hair. Owing to this ease of extraction, which is important in order to obtain pure melanins, but also because we had in mind an analysis of the phenogenesis of melanic pigmentation3,4, we have studied chiefly melanins from rabbits of known genotypic constitution. Nevertheless, the similarity of the data for mammalian hair melanins generally with those for rabbit hair melanins suggests that our conclusions are applicable to hair melanins in general and to melanins of other tissues.

Chemical Constitution of the Nucleolar Inclusions in Growing Oocyte Cells

Abstract: IN many animals during the second period of growth of the oocyte there is a production of nucleolar substance by means of a multiplication of numerous little nucleoli, or the budding of small nucleoli from a principal nucleolus1. When a principal nucleolus exists, in general concomitantly with the production of the buds, some inclusions with a more or less vacuolar appearance are formed in its interior1. In a study of the nucleolar physiology in two species of Helicidae—Helix aspersa Mull, and Tachea nemoralis L.—we have examined the constitution of these inclusions. They are not aqueous vacuoles; though they can be, and probably in general are, less dense than the body of the nucleolus; when centrifuged they are not markedly dislocated and in concentrated salt solutions the volume of the inclusions does not diminish more than the rest of the nucleolus.

A possible explanation of the relations between hereditary anaemias and depigmentation in the mouse.

Abstract: IN mice there are two chief forms of hereditary anaemias, the macrocytic and the siderocytic or flexed tail anaemia1. The former is due to one of the dominants W or Wv, the first of which is lethal when homozygous while the second is viable. WW and WvWv animals are white with black eyes, and in the heterozygotes with the normal w the two factors may or may not show dominance, according to the factor concerned and the genetic background2. The other form of anaemia, the siderocytic, is due to the recessive factor f and is also associated with depigmentation. All the ff animals show a transitory anaemia at birth, and the majority of them have also a white spot on the belly and many times also a flexed tail.

Relation of lipid metabolism to migration in birds; seasonal variation in body lipids of the migratory white-throated sparrow.

Abstract: mnent present in the feathers of birds. The brown and purple pigments of each species appeared to be identical chromatographically and spectroscopically with the corresponding pigments of the other species studied. Observations indicate that quantitative differences in total pigment and the relative proportions of the different pigments within and between species may account for differences in observed color of red feathers and hair.

Structure and Chemistry of Nucleoli

Abstract: Publisher Summary This chapter discusses the structure and chemistry of nucleoli Nucleoli are generally described as homogeneous, spheroid, and intranuclear bodies that have an affinity for eosin in hematoxylin-eosin preparations but are basophilic in basic dye solutions However, the presence of vacuoles and inclusions of various kinds is widely recognized Studies of electron micrographs of thin sections of nucleoli shows that the nucleolus contains two structural phases: one being essentially structureless, the other being a fine, highly coiled, stranded material The electron micrographs reveal no indication of a limiting membrane around the nucleolus The nucleolus in plants is associated with a particular region of a given chromosome This region is characterized by its lack of staining with the Feulgen reaction for desoxyribonucleic acid (DNA) In the interphase, the nucleolus becomes hypertrophied during anabolic activity of the cell, and conversely becomes smaller during drastic catabolic states A number of experimental analyses exhibit that the nucleolus is composed of concentrated protein with variable amounts of ribonucleic acid (RNA)

Histochemical tests for proteins and amino acids; the characterization of basic proteins.

Abstract: For cytophysiological work it is important to have ways of demonstrating proteins and amino acids and especially of characterizing basic and non-basic proteins. The author presents a review of the more usually employed histochemical reactions for amino acids and proteic compounds in general, with several modifications which increase their sensitivity, or specificity and localization. The author describes the histochemical arginine reaction, recently introduced by him, by means of which the characterization of basic and non-basic proteins can be easily accomplished in every laboratory without costly apparatus; this reaction serves also for the demonstration of proteins in general. The application of protein histochemical tests for quantitative purposes is discussed in connection with the characterization of the basic proteins and the determination of the relative concentration and the active metabolic changes of proteic compounds.