ULTRASTRUCTURAL LOCALIZATION OF COMPLEX CARBOHYDRATES AND PHOSPHATASES IN DIGESTIVE GLAND CELLS OF FEEDING AND HIBERNATING SNAILS, HELIX LUCORUM (GASTROPODA: HELICIDAE)

The digestive gland of normally-fed snails Helix lucorum, aswell as that of snails which had hibernated for 4 months wereexamined by the use of cytochemical techniques for detectionof acid and alkaline phos-phatase, as well as of periodate-reactive(PA-TCH-SP technique), sulfated (HID-TCH-SP technique) and carboxylatedcarbohydrates (LID-TCH-SP technique). The cytochemical resultssupport the hypothesis of intracellular digestion via lysosomalactivity of material taken up by endocytotic processes by thecells of the digestive gland. Four months hibernation did notaffect the intracellular distribution of polysac-charides andphosphatases in the cells of the digestive gland of H. lucorumcompared to that in the control snails. In addition, hibernationaffected the percentage of the calcium cells which significantlyincreased compared to the non-hibernating snails, whiie thepercentages of the digestive and excretory cells remained almoststable. However, the periodate-reactive sulfated and carboxylatedpolysaccharides of the digestive gland cells decreased in thehibernated snails compared to the controls. The results suggestthat the cytochemistry of periodate-reactive, sulfated and carboxylatedpolysaccharides used in the present study could, also, be appliedto the study of lysosomal activities. (Received 1 October 1991; accepted 4 December 1991)     

The role of biofoam in shielding spittlebug nymphs (Insecta,Hemiptera, Cercopidae) against bright light

1. Biofoam in spittlebugs has traditionally been seen as a defence against predation and a microclimate that reduces the risks of overheating and drying out. This study addresses the possible role of the foam as a light attenuator. 2. Nymphs exhibit higher mortalities when reared under brighter light (1800–2000 lux) than under less bright light (600–800 lux). At all developmental stages, photoavoidance is strongest when the nymphs are depleted of foam covers. First‐ and second‐instar nymphs appear to be the most vulnerable to exposures by bright light. 3. Smaller bubbles are more effective as light attenuators than are larger ones. As younger instars possess smaller canals from which bubbles are released and, furthermore, exhibit higher concentrations of proteins in bubble liquid, they can produce smaller‐sized bubbles and their foams are more effective at reducing light than are those of older nymphs. 4. The findings of this study show that most of the visible and UV radiation is reflected by the foam: transmittance of visible light was 15% at 600 nm and 12% at 350 nm. 5. These results demonstrate that spittlebug foam also possesses properties that render it an effective barrier against potentially damaging solar radiation.     

Mutant p21ras in vinyl chloride exposed workers

The production of mutations in cellular oncogenes such as ras is involved in the development of many human cancers. These mutations result in the expression of mutant forms of the encoded p21 protein which can potentially serve as a biomarker for this carcinogenic process. Workers exposed to vinyl chloride (VC) who are at risk for the development of the sentinel neoplasm angiosarcoma of the liver (ASL) represent a model population for the study of such a mutant p21ras biomarker, since VC is known to cause a specific ras mutation in ASL. In order to determine the relationship between VC exposure and this biomarker, serum samples from a cohort of 225 French VC workers and 111 age-sex-race-smoking-drinking matched unexposed controls were examined for the presence of mutant p21ras by immunoblotting with a mouse monoclonal antibody specific for the mutant protein. Stratifying the exposed workers by degree of VC exposure in estimated ppm-years by quartiles yielded a statistically significant trend for increasing odds ratio for sero-positivity of the p21ras biomarker with increasing exposure. These results suggest that this serum biomarker is related to VC exposure and may be an early indicator of carcinogenic risk in exposed individuals.     

A NEW TRAVERSODONTID CYNODONT (THERAPSIDA, EUCYNODONTIA) FROM THE MIDDLE TRIASSIC SANTA MARIA FORMATION OF RIO GRANDE DO SUL, BRAZIL

Abstract:  Remains of a peculiar traversodontid cynodont, Protuberum cabralensis gen. et sp. nov., are described herein. The material was collected from two outcrops representing the Therapsid Cenozone (Middle Triassic) of the Santa Maria Formation, and consists of a cranium with most of its dentition preserved and an associated postcranial skeleton. The upper postcanines have two sharp cusps that are connected by a medial crest on unworn postcanines. The specimens possess several autapomorphies, including: (1) presence of thickened bone on the dorsal surface of the skull; (2) thick dorsal ribs, with remarkable processes situated on their dorsal borders that decrease in size distally; and (3) an iliac blade with a series of rugosities along its dorsal border. The lumbar ribs bear overlapping costal plates and have distally projecting rib shafts that differ from the pattern observed in Thrinaxodon , Pascualgnathus and Cynognathus .     

FORMATION OF JOINED LARVAE IN THE STARFISH, ASTERINA PECTINIFERA

A method for joining larvae in the starfish, Asterina pectinifera , is presented. Any number of embryos are stably united by simple contact of the cell clusters (descendents of individual denuded eggs) before reaching the early blastula stage (ca. 6 1/2 hr after insemination at 21°C). Embryos do not combine with each other after closing into hollow blastulae. This is considered to indicate the transformation of the cell cluster from a mere collection of cells to an individual, multicellular system. Biological meanings of the fertilization membrane are discussed.