Human hepatoma (HepG2) cells secrete a single 65 K dalton triglyceride lipase immunologically identical to postheparin plasma hepatic lipase

A triacylglycerol lipase was isolated from the culture medium of HepG2 human hepatoma cells and its properties were compared to hepatic triglyceride lipase (H-TGL) from human postheparin plasma. The HepG2 cell enzyme bound to heparin-Sepharose, was eluted with 1 M NaCl and was not inhibited by 1 M salt. Western-blotting of the fractions from the heparin-Sepharose column with a monoclonal antibody prepared against postheparin plasma H-TGL and which binds to an epitope in the carboxyl-terminus of H-TGL gave a single immunoreactive protein band of 65 kDa. This finding of immunochemical identity was confirmed with polyclonal antibodies prepared against synthetic peptides of H-TGL corresponding to amino acid residues 82-94 near the amino-terminus and residues 468-477, the carboxyl-terminus of the enzyme. We conclude that HepG2 cells secrete a single triacylglycerol lipase with molecular weight properties and immunological characteristics identical to post-heparin plasma H-TGL.     

Localization of the structural difference between bovine blood coagulation factors X1 and X2 to tyrosine 18 in the activation peptide

Bovine Factor X is isolated in two chromatographically separable forms, Factor X1 and Factor X2. Whereas only a single form of Factor Xa, the active protease, exists, the activation peptides also exist as two chromatographically distinct species. These peptides have been shown to differ at a tyrosyl residue by ultraviolet spectrophotometry, and in their composition after alkaline hydrolysis. On the basis of the spectral properties, and elution position of the modified tyrosine on Dowex 1 columns and on an amino acid analyzer, it has been concluded that Factor X2 contains a tyrosyl-O-SO4 residue at position 18 in the activation peptide whereas Factor X1 contains only tyrosine. Alternative explanations such as differences in carbohydrate composition, differences in phosphate content, or differences in the number of gamma-carboxyglutamic acid residues were demonstrated to be unrelated to the difference in chromatographic behavior between bovine Factors X1 and X2.     

Reduction of plant tissue nitrate to nitric oxide for mass spectrometric 15N analysis.

A procedure based on that of Van Slyke and LoMonte (Microchem. J.14, 608–626, 1969) is described for the mass spectrometric analysis of ¹⁵N in nitrate extracted from plant tissue. The extract is evaporated to dryness in a disposable borosilicate test tube, which forms the basal part of a reaction flask. After evacuation of the flask, nitrate is reduced to nitric oxide by sonication with mercury in 18 n H₂SO₄. The atom percentage ¹⁵N is calculated from the relative intensities of the ¹⁴NO and ¹⁵NO peaks of the mass spectrum. The method is unaffected by reduced nitrogen compounds which are present in plant tissue extracts.     

Comparative protective actions of gonadotrophins and testosterone against the antispermatogenic action of ethane dimethanesulphonate

After a single dose of ethane dimethanesulphonate (EDS) (75 mg/kg) to rats the prolonged antispermatogenic action is due to a temporary elimination of the functional Leydig cell population. Replacement therapy with testosterone propionate (3 mg/day) maintains the spermatogenic epithelium but the EDS effect develops when hormone treatment is discontinued. In contrast, a short treatment with hCG (10-100 i.u./day) or LH (714 micrograms/day), starting before the EDS dose, permanently protects the spermatogenic epithelium. FSH treatment was completely ineffective. Although histological protection of spermatogenesis appeared complete with testosterone or hCG, effects on fertility remained but over different periods of time. Antispermatogenic and antifertility effects were produced in mice using much higher doses of EDS (5 X 250 mg/kg) but there was no protection from androgen or hCG. It is suggested that EDS binds to Leydig cells irreversibly, interfering with the action of gonadotrophin. At the dose level used the evidence suggests that the degree of reaction renders most of the Leydig cell population non-viable. A direct cytotoxic effect of the compound upon the spermatogenic epithelium might account for the inability of testosterone or hCG alone or in combination to maintain fertility at normal levels.     

Predatory and nesting behaviour of Cocalus gibbosus,a spartaeine jumping spider (Araneae: Salticidae) from Queensland

Abstract

Cocalus gibbosus was studied in the field in Queensland and in the laboratory. This is the first behavioural study of a species from the spartaeine genus Cocalus. C. gibbosus often omitted elements which are usually present in the predatory sequences of typical salticids and tended to lunge at prey from close range rather than leap from afar. Experiments showed that C. gibbosus prefers moths to other prey. In nature, C. gibbosus moulted and oviposited on silk sheets spun against tree trunks, and in the laboratory on sides of cages or blocks of wood, but this species never built an enclosing nest like typical salticids nor a large prey-catching web like some other spartaeines. C. gibbosus stalked across alien webs to catch spiders and insects, but it did not make vibratory signals. It did not stick to cribellate or ecribellate glue on alien webs. The behaviour of C. gibbosus is compared to that of other spartaeine salticids.     

Learning and Exposure Affect Environmental Perception Less than Evolutionary Navigation Costs

Most behaviors are conditional upon successful navigation of the environment, which depends upon distance perception learned over repeated trials. Unfortunately, we understand little about how learning affects distance perception–especially in the most common human navigational scenario, that of adult navigation in familiar environments. Further, dominant theories predict mutually exclusive effects of learning on distance perception, especially when the risks or costs of navigation differ. We tested these competing predictions in four experiments in which we also presented evolutionarily relevant navigation costs. Methods included within- and between-subjects comparisons and longitudinal designs in laboratory and real-world settings. Data suggested that adult distance estimation rapidly reflects evolutionarily relevant navigation costs and repeated exposure does little to change this. Human distance perception may have evolved to reflect navigation costs quickly and reliably in order to provide a stable signal to other behaviors and with little regard for objective accuracy.