Neurobehavioral effects from exposure to dental amalgam Hg(o): new distinctions between recent exposure and Hg body burden

Potential toxicity from exposure to mercury vapor (Hg(o)) from dental amalgam fillings is the subject of current public health debate in many countries. We evaluated potential central nervous system (CNS) toxicity associated with handling Hg-containing amalgam materials among dental personnel with very low levels of Hg(o) exposure (i.e., urinary Hg <4 microg/l), applying a neurobehavioral test battery to evaluate CNS functions in relation to both recent exposure and Hg body burden. New distinctions between subtle preclinical effects on symptoms, mood, motor function, and cognition were found associated with Hg body burden as compared with those associated with recent exposure. The pattern of results, comparable to findings previously reported among subjects with urinary Hg >50 microg/l, presents convincing new evidence of adverse behavioral effects associated with low Hg(o) exposures within the range of that received by the general population.     

Craf-1 protein kinase is essential for mouse development

The complete cDNA of the mouse integral membrane protein 2B gene (Itm2b) was determined by sequence analysis of expressed sequence tag (EST) clone L26775 and a clone isolated from a cDNA library of the osteogenic stromal cell line MN7 (Mathieu et al., 1992. Calcif. Tissue Int. 50, 362-371) and by 5' rapid amplification of cDNA ends (RACE). Alignment of different mouse ESTs confirmed the entire sequence. Northern blot analysis of different neonatal and adult mouse tissues showed that Itm2b is ubiquitously expressed. There are three mRNAs with different lengths in neonatal as well as in adult tissues, originating from alternative polyadenylation by usage of one consensus and two additional variant polyadenylation signals. The cDNA sequence of the human Itm2b homolog (ITM2B) was assembled using data from available human ESTs. Both the mouse and the human gene code for a protein of 266 amino acids (aa) that is homologous to a previously described integral membrane protein, Itm2A, of which the expression is restricted to osteo- and chondrogenic tissues. Itm2A and Itm2B belong to a family of type II integral membrane proteins, which contains a third member, Itm2C (Deleersnijder et al., 1996. J. Biol. Chem. 271, 19475-19482). The human ITM2B and mouse Itm2b genes were previously mapped as unknown ESTs to conserved syntenic regions Homo sapiens 13q12-13 and Mus musculus 14.     

Overtraining and glycogen depletion hypothesis

Low muscle glycogen levels due to consecutive days of extensive exercise have been shown to cause fatigue and thus decrements in performance. Low muscle glycogen levels could also lead to oxidation of the branched chain amino acids and central fatigue. Therefore, the questions become, can low muscle glycogen not only lead to peripheral and central fatigue but also to overtraining, and if so can overtraining be avoided by consuming sufficient quantities of carbohydrates? Research on swimmers has shown that those who were nonresponsive to an increase in their training load had low levels of muscle glycogen and consumed insufficient energy and carbohydrates. However, cyclists who increased their training load for 2 wk but also increased carbohydrate intake to maintain muscle glycogen levels still met the criteria of over-reaching (short-term overtraining) and might have met the criteria for overtraining had the subjects been followed for a longer period of time. Thus, some other mechanism than reduced muscle glycogen levels must be responsible for the development and occurrence of overtraining.     

Neurophysiologic study of beta-thalassemia patients

Neurophysiologic investigations were performed in 34 Chinese patients with beta-thalassemia major maintained on long-term desferrioxamine treatment to look for subclinical toxicity in the auditory, visual, peripheral, or central neural pathways. In the auditory pathway study, four patients (12%) had mild sensorineural hearing impairment. Two patients (6%) had increased P 100 latencies in the visual evoked potential study, and nine patients (26%) had abnormal electroretinogram results. All had normal electrooculograms. Ophthalmoscopic examination was abnormal in three patients (9%), and three (9%) had a visual field defect. In the peripheral or central nervous pathways, seven patients (21%) had sensory neuropathy, of which three cases were probably related to diabetes mellitus. All had normal motor conduction velocities. Four patients (12%) had increased cortical latencies of median or posterior tibial somatosensory evoked potential. Abnormalities in multiple neural pathways were seen in four patients (12%). There was a significant association between subclinical toxicity to the peripheral or central nervous systems and serum ferritin level (P < .03) and the presence of diabetes mellitus (P < .002). There was no significant relationship between the age, dosage, or duration of desferrioxamine used and the increased risk of neurotoxicity to the auditory, visual, peripheral, or central nervous systems. There was also no association between the risk of neurotoxicity and the serum zinc, copper, or fructosamine levels.     

Object-oriented experiences with ERIC

The authors have developed an architecture simulation toolkit from which a RISC simulator has been built by employing object-oriented software development techniques. Object-oriented design makes it easy to extend the simulated RISC architecture. Equally, more or even different functionality can be incorporated by uniformly extending the framework of the simulator. The basic framework is explained by simulating a subset of the Acorn ARM RISC's instruction set. This instruction set is then extended to provide further functionality by the addition of a multiply with accumulate instruction. The reader is expected to be reasonably conversant with the C++ programming language and with the basic concepts of object-oriented programming.     

非均质油藏压力数据分析——井筒存储和表皮效应

我们认为一个非均质油藏中的一口井完成后，它的渗透率是位置的函数；而且我门要研究受蟛筒存储和表皮效应影响的数据分析结果（用来估算表皮效应的压力降落的方法已经提供）。显示出如果井筒存储效应很小或者可以用反卷积去掉。那么，就可以算出等效的径向渗透率分布。通过结合等效的渗透率分布和合理确定的表皮系数估算值，可以得到有应用价值的油井动态长期预测。     

Regulation of matrix synthesis rates by the ionic and osmotic environment of articular chondrocytes

Chondrocytes in cartilage are embedded in a matrix containing a high concentration of proteoglycans and hence of fixed negative charges. Their extracellular ionic environment is thus different from that of most cells, with extracellular Na+ being 250-350 mM and extracellular osmolality 350-450 mOsm. When chondrocytes are isolated from the matrix and incubated in standard culture medium (DMEM; osmolality 250-280 mOsm), their extracellular environment changes sharply. We incubated isolated bovine articular chondrocytes and cartilage slices in DMEM whose osmolality was altered over the range 250-450 mOsm by Na+ or sucrose addition. 35S-sulphate and 3H-proline incorporation rates were at a maximum when the extracellular osmolality was 350-400 mOsm for both freshly isolated chondrocytes and for chondrocytes in cartilage. The incorporation rate per cell of isolated chondrocytes was only 10% that of chondrocytes in situ both 4 and 24 hours after isolation. For freshly isolated chondrocytes, the rate increased 30-50% in DMEM to which NaCl or sucrose had been added to increase osmolality. In chondrocytes incubated overnight in DMEM, the rate was greatest in DMEM of normal osmolality and fell from the maximum in proportion to the change in osmolality. The effects of sucrose addition on incorporation rates were similar but not identical to those of Na+ addition. Changes in cell volume might be linked to changes in synthesis rates since the cell volume of chondrocytes (measured by Coulter-counter) increased 30-40% when the cells were removed from their in situ environment into DMEM. Synthesis rates can thus be partly regulated by changes in extracellular osmolality, which in cartilage is controlled by proteoglycan concentration. This provides a mechanism by which the chondrocytes can rapidly respond to changes in extracellular matrix composition.