Neonatal rat hepatocytes in primary tissue culture free from density-dependent regulation of growth

Summary Studies employing [³H]thymidine and radioautography as well as colchicine and Feulgen staining of DNA showed that up to 19-fold increases in the degree of cell crowding in vitro, i.e. from 1.45 to 27.55×10⁴ cells per specimen, did not change the rates of entry into DNA synthesis and mitosis of cultivated primary neonatal rat hepatocytes.     

Effects of purine cyclic nucleotides on the growth of neonatal rat hepatocytes in primary tissue culture

cGMP and db-cGMP administered for 20–24 h to neonatal rat hepatocytes in primary culture stimulated their DNA synthesis and proliferation only at concentrations higher than the physiological one, whereas at concentrations equal to or lower than the physiological concentration they were ineffective or inhibitory for both activities. Induction of DNA synthesis to be effected by cGMP required 15 h of treatment, preceded, however, by inhibition of the same process between the 6th and the 14th hour of exposure. In contrast, cAMP and db-cAMP stimulated the flow of cultivated hepatocytes into the S and M stages of their mitotic cycle when administered at very wide concentration range, including the physiological for cAMP and the sub-physiological for db-cAMP. cAMP was effective after 12–14 h of treatment. Equimolar mixtures of cGMP with cAMP and of db-cGMP with db-cAMP also stimulated the proliferative activity of primary hepatocytes, but only at very low doses, which induced a first peak of DNA synthesis between the 2nd and the 6th hour of treatment and a second peak at about the 18th hour. These actions of the cyclic compounds, employed singly or in equimolar combination, were shown to be specific, since they could not be reproduced by their main metabolites. The present results strengthen the view that cAMP plays a pre-eminent role in the positive regulation of hepatocyte proliferation. Contrary to the postulate of the dualistic doctrine, cGMP by itself is not proliferogenic in the physiological range; in fact, cGMP acts as an ancillary, possibly dispensable, compound whose physiological role may be to help, in cooperation with cAMP, liver cells to cross the G1/S boundary of their growth-division cycle.     

A cytochemical approach to the wound repair mechanism inUdotea petiolata (Siphonales)

Summary When injured, the thalli of the coenocytic algaUdotea petiolata undergo a rapid sealing process mainly due to the extrusion of two successive plugs. In the first, external and transitory plug, sulphated polysaccharides are the predominant components. In the second, permanent and internal plug, roundish bodies having a complex polysaccharidic composition are embedded in a fibrillar matrix of still unknown nature. The sulphated sugars were identified and located by means of Alcian Blue staining and X-ray microanalysis. A periodic acid-thiocarbohydrazide-silver proteinate technique proved useful especially in the study of the roundish bodies and in the compositional and structural comparison of the siphon wall with the wound wall. Phosphotungstic acid at low pH was used to evidentiate an extensive plasma membrane activity in the repairing cytoplasm.Supported by a grant of C.N.R.     

MICROHETEROGENEITY OF BRAIN CYTOPLASMIC AND SYNAPTOPLASMIC ACTINS

Abstract— Actin present in whole rat brain cytoplasm and in synaptosomes was purified by DNase I affinity chromatography. By use of two-dimensional gels and one-dimensional isoelectric focusing gels, brain actin was shown to be composed of two isomeric forms. By comparison with muscle actins, brain actins were identified as the β and γ isomers. Muscle type α actin is not present in brain. Synaptosomal protein with high affinity for DNase I is primarily composed of β and γ actin, however, two minor synaptosomal proteins, S₁ and S₂, with similar DNase I affinity were also isolated. S₁1 and S₂ have the same apparent molecular weight as whole brain actin, are more acidic than the major actin forms and are distinct from a actin. Relative to β and γ actin, the content of S₁ and S₂ is 3-fOld greater in synaptosomes when compared to similar non-synaptosomal species. The results demonstrate heterogeneity of brain actins and compartmentalization of brain proteins with high affinity for DNase I at the synapse. It was also shown that tubulin has selective affinity for the DNase I-actin complex.     

Cannibalism in prehistoric Europe

The key argument for the identification of prehistoric cannibalism is provided by analysis of close similarities in the treatment of human and animal remains. Such analysis requires precise data on depositional context, meticulous excavation records, detailed bone modification studies, a relatively large sample of human and animal postcranial bones, and data on local mortuary practices. With the exception of Fontbrégoua Cave, these necessary conditions are lacking at all Stone Age European sites where it has been hypothesized that cannibalism occurred. The alternative hypothesis of secondary burial practices has been proposed informally for some sites and, in a more formal and detailed way, for Krapina and Fontbrégoua. However, this hypothesis does not have a higher probability, is not justified by current data, and uses ethnographic analogies to prop up interpretations of materials for which contextual data are missing or have been neglected. At Fontbrégoua, cannibalism remains the simplest and most plausible explanation of the evidence; at Krapina and other sites the available evidence is insufficient to prove either secondary burial or cannibalism.     

Sesquiterpenes from Lactarius blennius

Six sesquiterpene lactones were isolated from Lactarius blennius. The structures of two new sesquiterpenes, blennin A and blennin B were determinated by spectroscopic methods and the structure of the seco-compound, blennin C, is revised. The two known furan sesquiterpenes and lactarorufin A were also identified.     

Non-enzymatic and microsome-dependent binding of polycyclic hydrocarbons to DNA and polynucleotides

The binding of tritium-labelled 7,12-dimethylbenz[a]anthracene (DMBA), benzo[a]pyrene (BP) and 3-methylcholanthrene (MCA) to DNA or polynucleotides in vitro was re-examined both in the presence and in the absence of rat liver or human placental microsomes.A high level of non-enzymatic binding was evident when thymus DNA was used as acceptor. This non-enzymatic binding made it difficult to determine the effect of microsomes, except in the case of BP when induced rat microsomes were used. Better results were obtained using polynucleotides: a definite microsome-dependent binding occurred between all the polynucleotides and all the hydrocarbons tested.No clear evidence of binding catalysed by microsomes from human placenta was found except in polynucleotide-BP interactions: further studies are required to completely evaluate the ability of such nucleic acid-microsomal system for testing in vitro possible oncogenic substances in animals and humans.     

Observations on the biology and behaviour of the predaceous miteTyphlodromus italicus [Acarina: Phytoseiidae] in peach orchards

The results of investigations onTyphlodromus italicus Chant in some peach orchards in the Verona district, where the predator is wide-spread, are described. Both field and laboratory studies have shown thatT. italicus grows rapidly (egg to adult 6 days at 25°C.) and has a long reproductive period, especially when prey is available. It speedily recovers in number and has a high prey-searching capacity. It is fast-moving, and its distribution over the tree corresponds to that of the phytophagous mites. It can live and reproduce on the tree in the absence of prey. A density of 50–60T. italicus/100 leaves is reached in August. FemaleT. italicus are found on leaves till November feeding whenever prey is available, and wintering in a mated condition in bark crevices. Many enter diapause in late autumn. Overwinter mortality is high. These characteristics enableT. italicus to play a very significant role in the control of peach mites and in orchards, which are unsprayed, it keeps their populations at a low density from spring to autumn.