Cleavage of adeno-associated virus DNA with Sali,Psti and Haeii restriction endonucleases.

Duplex AAV-2 DNA was digested with SalI, PstI or HaeII restriction endonucleases and the cleavage sites were mapped. SalI cleaves AAV DNA at 0.310 map units, PstI at 0.106, 0.422 and 0.914 and the five HaeII sites were mapped at 0.110. 0.156, 0.181, 0.536 and 0.600 map units. These cleavage products will be useful for the isolation of specific regions from the AAV DNA, located outside of the stably transcribed region of the genome, and will also help to map more complex restriction enzyme cleavages.     

The cytology of Brachycome lineariloba

Brachycome lineariloba race A (n=2) contains at least four cytodemes designated A₁, A₂, A₃ and A₄ which differ in karyotype and geographical distribution. Data from chromosome morphology, patterns of early and late condensing chromatin and heterochromatin and meiotic pairing are presented.—These show that A₂, A₃ and A₄ differ by loss or suppression of nucleolar organisers. A₄ has a nucleolar organiser on both chromosomes and is likely to be primitive. A₁ differs by interchange. There has been some conversion of early to late condensing chromatin. All the cytodemes show karyotypic polymorphism.     

NS-4 (nervous system antigen-4), a cell surface antigen of developing and adult mouse brain and sperm.

Morphological changes in the chorion of the Medaka, Oryzias latipes, brought about by the hatching enzyme were examined by transmission as well as scanning electron microscopy. The structure of the intact chorion, especially its thick multilamellar inner layer, does not change during development until about 1 hr before the onset of hatching. As choriolysis proceeds, the inner layer of the chorion is digested to yield soluble proteins of relatively high molecular weight. During this process it appears that each lamella is successively solubilized from the inner surface of the chorion. Finally, a thin outer layer with accompanying villi and attaching filaments remains.Under the experimental conditions used, the enzyme was in direct contact with both the inner and outer layers of the chorion. Because of this, the enzyme could penetrate the outer layer and act on some peripheral parts of the underlying inner layer. Based on these morphological changes, a mechanism is proposed to account for the solubilization of the chorion by the hatching enzyme.     

Changes in tight junctions of thyroid epithelium with changes in thyroid activity

The morphology of the tight junction of rat thyroid epithelium was examined in freeze-fractured material fixed in glutaraldehyde and briefly glycerinated. In normal thyroids the overall appearance of this junctional specialization resembled that of other cell types in many respects. Short-term changes in thyroid activity and hypophysectomy for 3 wk did not obviously affect the appearance of tight junctions. Feeding of the goitrogen, thiouracil, which stimulates secretion of thyroid-stimulating hormone, resulted in the appearance of some very narrow and some very wide, tight junctions or sometimes junctions with both wide and narrow regions within the same cell.     

Hapten-sandwich labeling. II. Immunospecific attachment of cell surface markers suitable for scanning electron microscopy

A hapten-sandwich procedure has been used for immunospecific labeling of cell surface antigens with markers visible by scanning electron microscopy. Antihapten antibody was used to link hapten-modified tobacco mosaic virus, bushy stunt virus, or hemocyanin to hapten-modified human erythrocytes. The antihapten antibody bridge was also used to link the hapten-virus marker to hapten-modified antibodies against mammary tumor virus on mouse mammary tumor cells, or against immunoglobulin receptors on mouse splenic lymphocytes. In all cases, labeling was highly specific. With this technique, it is possible to (a) compare morphological features of cells bearing differing cell surface antigens, and (b) examine the arrangement of specific antigenic sites on a cell surface or their distribution relative to membrane structures such as microvilli.     

Studies on enzyme variation in the murine malaria parasites Plasmodium berghei, P. yoelii, P. vinckei and P. chabaudi by starch gel electrophoresis.

Electrophoretic variation of the enzymes glucose phosphate isomerase, 6-phosphogluconate dehydrogenase, lactate dehydrogenase and glutamate dehydrogenase (NADP-dependent) has been studied in the African murine malaria parasites Plasmodium berghei, P. yoelii, P. vinckei and P. chabaudi and their subspecies. Horizontal starch gel electrophoresis was used throughout. The number of isolates examined in each subspecies varied from 1 (P. y. nigeriensis) to 24 (P. c. chabaudi). Extensive enzyme variation was found among isolates of most of the subspecies from which more than two such isolates were available for study. It is clear that the phenomenon of enzyme polymorphism is of common occurrence among malaria parasites. With the exception of P. berghei and P. yoelii, of which all isolates share an identical electrophoretic form of lactate dehydrogenase, no enzyme forms are shared between any of the 4 species of murine plasmodia. By contrast, within each species common enzyme forms are shared among each of the subspecies. The subspecies are nevertheless, distinguished from each other by the electrophoretic forms of at least one enzyme. The distribution and reassortment of enzyme variation among isolates of a single subspecies is in accordance with the concept of malaria parasites as sexually reproducing organisms. The study of variation among parasites present in individual wild-caught rodent hosts demonstrates that natural malarial infections usually comprise genetically heterogeneous populations of parasites. Nevertheless, the number of genetically distinct types of parasite of any one species present in a single infected host appears to be small. Generally not more than 2 or 3 clones of parasite of distinct genetic constitution are present in a single infected animal.