The origin and structure of the secondary coat of the egg of Drosophila melanogaster

Summary The techniques of light and electron microscopy have been employed in a study of the protective coverings of the egg of Drosophila melanogaster. Data obtained during this investigation suggest the involvement of the follicle cells, in the production of one of these coverings and justify its classification as a secondary coat. The secondary coat of D. melanogaster is highly organized and has been divided into three Zones (I, II, IIII). The follicle cells enveloping the oocyte exhibit two phases of secretory activity each involving hypertrophy of the Golgi complex and rough endoplasmic reticulum, and the production of protein and polysaccharide components. The first phase concerns the elaboration of the material which gives rise to the homogeneous lamina referred to as Zone I. The second results in the release of an electron dense component which becomes organized into two laminae separated by struts or pillars; this construction is referred to as Zone II. At the completion of this secretory phase, the follicle cells assume a squamous morphology and a third Zone, composed of a homogeneous substance, appears between the follicle cells and Zone II.This investigation was supported by grant GM-08776 to one of us (EA) from the National Institutes of Health, United States Public Health Service.     

Endotheliochorial Placentation in a Pangolin,Manis tetradactyla

The placenta of a pangolin, Manis tetradactyla, was examined grossly and histologically. The placenta was arranged in longitudinal bands of 2–3 mm width. Microscopically there was a deep labyrinth and an underlying layer of distended endometrial glands. A narrow junctional zone was present containing syncytiotrophoblast. Thoughout the labyrinth cytotrophoblast and syncytiotrophoblast were observed in contact with maternal capillaries. The placentation was considered to be endotheliochorial in type.     

Herpes simplex virus type 1 immediate-early protein Vmw110 reactivates latent herpes simplex virus type 2 in an in vitro latency system.

Reactivation of latent herpes simplex virus type 2 (HSV-2) by the immediate-early protein Vmw110 was studied by using an in vitro latency system. Adenovirus recombinants that express Vmw110 reactivated latent HSV-2. An HSV-1 mutant possessing a deletion in a carboxy-terminal region of Vmw110 reactivated latent HSV-2, whereas mutant FXE, which has a deletion in the second exon, did not. Therefore, Vmw110 alone is required to reactivate latent HSV-2 in vitro, and the region of Vmw110 defined by the deletion in FXE is important for this process.     

Hormonal stimulation of tyrosinase activity in human foreskin organ cultures

Summary A human foreskin organ culture system has been developed to study the response of human skin to hormonal stimulation. Foreskins are maintained in culture on floating plastic supports which allows the epidermal surface to be exposed to air while the dermis is bathed in nutrient medium. Both black and white human foreskins can be maintained in organ culture for at least 1 wk with no change in the tissue structure or cell viability as determined by histochemical staining and by dopa reaction staining. Tyrosinase activity in both black and white human foreskin cultures decays markedly during the first 2 d of culture to a new steady state level which remains stable throughout the culture period. Both black and white foreskin cultures consistently demonstrate 2- to 10-fold increases in tyrosinase activity when treated with theophylline (1 mM). Approximately 90% of all skin cultures examined showed an increase in enzyme activity when treated with this phosphodiesterase inhibitor. Dibutyryl cAMP (0.1 mM) and [Nle⁴, D-phe⁷]-alpha MSH (10⁻⁸ M), were also found to markedly stimulate tyrosinase activity in some skin cultures, whereas alpha-MSH and prostaglandin E₁ produced only an inconsistent and small increase in the activity of the enzyme. Histamine (1 μM), vitamin D₃ (1 μM), and retinoic acid (1μM) failed to stimulate tyrosinase activity in either white or black foreskin cultures. This hormone-responsive organ culture system can be utilized to characterize the molecular processes responsible for the regulation of tyrosinase and pigmentation in human skin. This work was supported by a research contract from the Oklahoma Center for the Advancement of Science and Technology (OCAST) and by a research grant from the Presbyterian Health Foundation.     

A Second Gene for Cerulean Cataracts Maps to the β Crystallin Region on Chromosome 22

Congenital cataracts are one of the most common major eye abnormalities and often lead to blindness in infants. At least a third of all cases are familial. Within this group, highly penetrant, autosomal dominant forms of congenital cataracts (ADCC) are most common. ADCC is a genetically heterogeneous group of disorders, in which at least eight different loci have been identified for nine clinically distinct forms. Among these, Armitageet al.(Nature Genet.9: 37–40, 1995) mapped a gene for cerulean blue cataracts to chromosome 17q24. Bodkeret al.(Am. J. Med. Genet.37: 54–59, 1990) described a large family with cerulean blue cataracts, in which the affected daughter of affected first cousins was presumed to be homozygous for the purported gene. We report linkage in this family to the region on chromosome 22q that includes two β crystallin genes (CRYBB2, CRYBB3) and one pseudogene (CRYBB2P1). The affected female in question is homozygous at all markers.     

Fine mapping of the Autosomal Dominant Split Hand/Split Foot Locus on Chromosome 7, Band q21.3-q22.1

Split hand/split foot (SHFD) is a human developmental defect characterized by missing digits, fusion of remaining digits, and a deep median cleft in the hands and feet. Cytogenetic studies of deletions and translocations associated with this disorder have indicated that an autosomal dominant split hand/split foot locus (gene SHFD1) maps to 7q21-q22. To characterize the SHFD1 locus, somatic cell hybrid lines were constructed from cytogenetically abnormal individuals with SHFD. Molecular analysis resulted in the localization of 93 DNA markers to one of 10 intervals surrounding the SHFD1 locus. The translocation breakpoints in four SHFD patients were encompassed by the smallest region of overlap among the SHFD-associated deletions. The order of DNA markers in the SHFD1 critical region has been defined as PON–D7S812–SHFD1–D7S811–ASNS. One DNA marker, D7S811, detected altered restriction enzyme fragments in three patients with translocations when examined by pulsed-field gel electro-phoresis (PFGE). These data map SHFD1, a gene that is crucial for human limb differentiation, to a small interval in the q21.3-q22.1 region of human chromosome 7.     

Minimizing growth regulators in shoot culture of an endangered plant,Hackelia venusta (Boraginaceae)

Summary Hackelia venusta (Boraginaceae) is an endangered perennial herb endemic to the interior northwestern United States. Because of seed scarcity, micropropagation (anex situ conservation strategy) could produce true-to-type plantlets suitable for reintroduction. We hypothesized that clones of predetermined size could be rapidly produced by supplementing multiplication and rooting media with minimal levels of cytokinin and auxin. Microshoots derived from shoot expants were cultured on Murashige and Skoog (1962) media supplemented with 1% (wt/vol) agar and 0.0001 to 10 μM benzyladenine. Inverse regression estimates on 3 genotypes predicted that a target of 2.5 axillary microshoots per explant would require a minimal level of 0.04±0.02 μM benzyladenine. Culture of 25 genotypes with 0.04 μM benzyladenine resulted in an average of 2.3±0.1 axillary microshoots per explant. Elongated microshoots were transferred to media supplemented with 0.1 to 25 μM indoleacetic acid. Clones rooted from 36% to 100% success after 4 wk in 2.0 μM indoleacetic acid. Plantlets transplantedex vitro with three or more roots survived at 84% versus 46% of plantlets with fewer roots. Up to 84% of the plantlets survived in a planting trial. The data suggest that shoot culture ofHackelia venusta, with minimal growth regulators, can produce axillary microshoots for reintroduction.