Black Rabbits Research Articles

Histidase activity of the skin in relation to the state of melanogenesis

The histidase reaction of the skin in relation to the state of melanogenesis was studied in animals (18 rabbits) and patients with vitiligo. The histidase activity and the content of urocanic acid were determined in skin biopsy material in order to study the reaction. The histidase activity of the skin of black rabbits was found to be twice as high as that of white rabbits. In the depigmented areas of the skin of patients with vitiligo the histidase reaction was depressed by comparison with areas of the skin with normal pigmentation in the same patients and with the skin of control persons. The dependence of the histidase reaction of the skin on the state of melanogenesis is dependent, it is suggested, on the inhibitory action of cysteine on the histidase and tyrosinase activity of the skin.

Multiple forms of tyrosinase in rodents and lagomorphs with special reference to their genetic control in mice.

AbstractPolyacrylamide gel electropherograms of extracts of pigmented hair bulbs from rodents and lagomorphs indicate that tyrosinase exists in multiple molecular forms. Allelic substitutions at the a, b, c, d, and p color loci in mice reveal that the multiple forms of tyrosinase are subject to complex genetic influences. Depending upon genic constitution, a maximum of three electrophoretically‐separable forms of tyrosinase (T1 = 80,000 m. w.; T2 = 62,000 m. w.; T3 = 66,000 m. w.) can be visualized by incubation of the polyacrylamide gels in L‐DOPA. In certain genotypes of mice, T1, T2, and T3 are either greatly reduced in activity or absent. Urea, SDS, and EDTA fail to dissociate tyrosinase suggesting that the multiple molecular forms of tyrosinase are not simple aggregates of monomeric subunits stabilized by non‐covalent bonds.Tyrosinase corresponding in mobility to the T1 of mice is also found in hair bulb extracts from black rats, black rabbits, gerbils and golden Syrian hamsters. The T2 and T3 components are distinct in the black rat but are represented by a single “T2‐T3” band in the gerbil, hamster and rabbit. An additional T0 band is found in the black rat. Available evidence suggests that T1 of comparable electrophoretic mobility is widely distributed in mammals and may be an additional indication of an underlying broad homology of pigmentary genes. At present, it is not certain whether the multiple forms of tyrosinase are “true” isozymes or a single enzymic moiety bound to structural components of the melanosomal matrix.

The melanizing activity of the semen of buffalo bulls and its relation to the proportion of liver spermatozoa.

Melanizing activity of rabbit semen was reported by Beatty (1956). The activity—colour reaction when semen is supplied with dihydroxyphenylalanine—varied between males with different pelt colours : black rabbits showed intense melanizing activity and albinos none. It was further observed that the pale colour of semen was a characteristic of dark pelted bucks, and that the colour of the semen was, in some way, related to its melanizing activity. Mukherjee (1964) studied the melanizing activity of the semen of bulls, goats and rams, and observed that the activity varied between animals and between ejaculates from the same animal. Although there was no appreciable relationship between the coat colour of these animals and the melanizing activity of the semen, the yellow semen samples showed stronger melanizing activity than the non-yellow ones. The proportion of 'live' (unstained in eosin-nigrosin) spermatozoa was uniformly less in strongly melanizing semen samples than in weakly melanizing

The Protection of Pancreatic Lipase by Acacia Gum

In this preliminary note we describe the results obtained by inoculation of the skin of the scrotum of four black rabbits with serous fluid expressed from an initial pinta lesion. The inoculation was made intradermally, as superficially as possible, with serous fluid rich in treponemata and diluted with normal salt solution. A papule appeared at the point of inoculation in one of the four rabbits on the 105th day. One hundred and fifteen days after inoculation the papule presented a circular erosion on an indurated base. The serous fluid expressed from this lesion contained numerous treponemata on dark-field examination, and these were easily impregnated by the Fontana-Tribondeau method. A volunteer inoculated with serous fluid expressed from the rabbit's lesion developed a typical initial pinta lesion at the point of inoculation, thus proving that the scrotal lesion of the rabbit was produced by Treponema carateum or Treponema herrejoni, the causal agent of pinta, mal del pinto or carate. Four rabbits inoculated with serous fluid from the scrotal lesion of the rabbit have not yet developed visible lesions.

The Experimental Transmission of Pinta, Mal del Pinto or Carate to the Rabbit

In this preliminary note we describe the results obtained by inoculation of the skin of the scrotum of four black rabbits with serous fluid expressed from an initial pinta lesion. The inoculation was made intradermally, as superficially as possible, with serous fluid rich in treponemata and diluted with normal salt solution. A papule appeared at the point of inoculation in one of the four rabbits on the 105th day. One hundred and fifteen days after inoculation the papule presented a circular erosion on an indurated base. The serous fluid expressed from this lesion contained numerous treponemata on dark-field examination, and these were easily impregnated by the Fontana-Tribondeau method. A volunteer inoculated with serous fluid expressed from the rabbit's lesion developed a typical initial pinta lesion at the point of inoculation, thus proving that the scrotal lesion of the rabbit was produced by Treponema carateum or Treponema herrejoni, the causal agent of pinta, mal del pinto or carate. Four rabbits inoculated with serous fluid from the scrotal lesion of the rabbit have not yet developed visible lesions.

SEX HORMONES AND HAIR CHANGES IN RATS

THE PROLONGED INJECTION of estradiol bensoate into male black rabbits has been reported to cause, after two and one-half to five months, first a change in hair color from black to red and then the development of symmetrical areas of alopecia; such effects were not seen in similarly treated female rabbits (I). There appears to be no information in the literature regarding hair changes in rats treated with estrogens and androgens. The observations to be reported, made incidental to experiments involving the administration of sex hormone pellets, seem worthy of record. The results to be described were observed during the prolonged treatment of normal adult male and female rats (2) with subcutaneous pellets of the following crystalline substances: testosterone dipropionate, androsterone, estrone, estradiol,α-estradiol benzoate, αestradiol dipropionate, estriol, equilin, diethylstilbestrol methyl ether (αα′-diethyl-4-hydroxy-4′-methoxy-stilbene), diethylstilbestrol methyl ether acetate (α,α′diethyl-4-acetyl-4′...

Societies and Academies

LONDON. Royal Society, March 25.—Sir William Crookes, president, in the chair.—Prof. B. Moore: The production of growths or deposits in meta-stable inorganic hydrosols.—Prof. B. Moore and W. G. Evans: Forms of growth resembling living organisms and their products slowly deposited from metastable solutions of inorganic colloids.—H. Onslow: A contribution to our knowledge of the chemistry of coat-colour in animals and of dominant and recessive whiteness.This research was undertaken in order to discover a chemical method of differentiating the two similar forms of white animals known as dominant whites and recessive whites, or albinos. Hitherto this has only been possible by observing their genetic behaviour. Dark animal pigments are believed to result from the oxidation of a colourless chromogen by an oxydase. The skins of young black rabbits were found to yield a tyrosinase which converted tyrosine to a melanin. By means of this tyrosinase it was possible to test extracts from white rabbits of both types. Briefly, extracts from dominant whites contained an anti-bxydase which inhibited the tyrosinase of the black rabbit extracts. Extracts from albinos, on the other hand, had no inhibiting influence, and were themselves incapable of producing any pigment. The anti-oxydase was also found in those white parts of rabbits which are dominant to colour, such as the white bellies of the wild rabbit and of the yellow rabbit carrying agouti. These results tend to confirm the Mendelian view that dominant whiteness is caused by a factor which inhibits the pigment-producing mechanism if present, and that albinism results from the partial or total absence of the factors necessary for the development of pigment. The experiments also revealed facts which suggest that the difference between pigments producing black, chocolate, and yellow hairs is quantitative rather than qualitative, for, after extraction, the pigments in all three colours appear identical. That variation in colour is a structural modification is supported by the fact that dilute colours, such as blue, are caused by a lack of pigment in the cortex. In the corresponding intense colours, such as black, pigment being present in the cortex, the white light reflected from the vacuoles is absorbed, thus deepening the colour,