Absence of right-left asymmetries in the rat hippocampus as demonstrated by Timm staining.

Although biochemical and behavioural studies have shown right-left differences in several areas of the rat limbic system, some anatomical studies reported no significant right-left differences in several morphological parameters of the hippocampus. The purpose of the present study was to determine whether there are asymmetries in the micro-anatomy of the rat hippocampus by examining the intensity of Timm staining in various hippocampal fields and the area occupied by mossy fibres by the use of combined microdensitometric and quantitative image analysis techniques. Timm staining demonstrates the distribution of intrahippocampal association pathways because it is a histochemical marker of zinc and other heavy transition metals. There were no right-left differences in the density of Timm staining at the level of the dentate gyrus, in the dendritic layer of CA1 and CA2 fields, in the mossy fibre area or in the subiculum. These findings provide further evidence of a lack of morphological asymmetry in the rat hippocampus.     

Desiccation of Panagrolaimus rigidus (Nematoda): survival,reproduction and the influence on the internal clock

Following the life-table experimental schedule, cohorts of aparthenogenetic strain of the free-living nematode Panagrolaimus rigidus were desiccated for six days at theages of4, 8, 12, and 19 d (age effect) and cohorts aged 8 d weredried for15, 20, 40, and 60 days (time effect) to determine theirability torecover and to reproduce.Nematode age had poor effect on recovery after 6 days ofdesiccation until the mean longevity of the nematode (19 daysinhydrated medium) is approached, while increasing times ofdesiccation (from 6 to 60 d) remarkably decreased capacity forrecovery (from 80 to 8%). Anhydrobiosis experienced atdifferentages or for different durations modified the timing of thenematodelife cycle events, but not the pattern of age-specificfecunditynor survival curves. The age-specific fecundity is largelyretainedfollowing anhydrobiosis, but when matched to that of thenematodeskept hydrated (controls), it declines for increasing durationsofdesiccation. Anhydrobiosis appears to cause a reset of theanimalsinternal clock, that is dependent on the duration ofdesiccation.     

Cleavage of the (1 goes to 3)-2-acetamido-2-deoxy-beta-D-glucopyranosyl linkage present in keratan sulfate. The A and B isoenzymes of human liver hexosaminidase (EC 3.2.1.30)

The disaccharide 2-acetamido-2-deoxy-beta-D-glucopyranosyl-(1 goes to 3)-D-[1-3H]-galactitol, prepared from keratan sulfate, was rapidly hydrolyzed by the A and B isoenzymes of normal human liver hexosaminidase (EC 3.2.1.30), and by the B isoenzyme prepared from the liver of a patient who had died of Tay-Sachs disease. The disaccharide substrate was also hydrolyzed by extracts of normal, cultured-skin fibroblasts, and fibroblasts of patients with Tay-Sachs disease, whereas it was not hydrolyzed by fibroblast extracts of patients with Sandhoff disease. Thus, effective degradation of keratan sulfate, secondary to a defect of the beta subunits present in the A and B isoenzymes of hexosaminidase, may contribute to the appearance of skeletal lesions in patients affected by Sandhoff disease.