Depressed basal hypothalamic neuronal activity in type-1 diabetic mice is correlated with proinflammatory secretion of HMBG1

We recently found indicators of hypothalamic inflammation and neurodegeneration linked to the loss of neuroprotective factors including insulin-like growth factor (IGF-1) and IGF binding protein-2 (IGFBP-3) in mice made diabetic using streptozotocin (STZ). In the current work, a genetic model of type-1 diabetes (Ins2(Akita) mouse) was used to evaluate changes in neuronal activity and concomitant changes in the proinflammatory mediator high-mobility group box-1 (HMBG1). We found basal hypothalamic neuronal activity as indicated by manganese-enhanced magnetic resonance imaging (MEMRI) was significantly decreased in 8 months old, but not 2 months old Ins2(Akita) diabetic mice compared to controls. In tissue from the same animals we evaluated the expression of HMBG1 using immunohistochemistry and confocal microscopy. We found decreased HMBG1 nuclear localization in the paraventricular nucleus of the hypothalamus (PVN) in 8 months old, but not 2 months old diabetic animals indicating nuclear release of the protein consistent with an inflammatory state. Adjacent thalamic regions showed little change in HMBG1 nuclear localization and neuronal activity as a result of diabetes. This work extends our previous findings demonstrating changes consistent with hypothalamic neuroinflammation in STZ treated animals, and shows active inflammatory processes are correlated with changes in basal hypothalamic neuronal activity in Ins2(Akita) mice

Sound levels in nursery schools

Introduction. Children and teenagers often suffer from hearing loss because of exposure to sound levels above 100 dB generated by toys, portable music players and stereo equipment in discotheques. Even in nursery schools and schools, considerable noise levels are produced by children's voices. Methods. Sound levels were measured in a nursery school in Cologne in four different rooms, each with 22 children aged between 3 and 6 years and two teachers. Sound dosimeters detected sound levels in each room for 5 days of the week. These were positioned in the room above the playing children as well as near the teachers' ears. The same measurements were repeated after the children had been instructed about noise and possible noise damage. In addition, the children were now able watch the noise lights, an instrument resembling traffic lights which translated the sound levels actually measured in their room into optical signals. A questionnaire containing 13 questions about noise and sensitivity to noise was distributed to 35 teachers at nursery schools in the Cologne municipal area. Results. Mean sound levels of an 8-h/day measuring period (L-eq) were 80.1 +/- 2.3 dB(A) near the ear of the teacher and 70.87 +/- 2.5 dB(A) measured in the room. The maximal sound level for 1 s, L-max dB(A), was 112.55 +/- 2.3 dB(A) near the ear and 103.77 +/- 8.1 dB(A) in the room. After the children had learned about noise and were able to check the sound level they produced with the help of the noise lights, a tendency towards a reduction of sound levels in the room and near the teachers'ears could be seen. An evaluation of the questionnaire revealed the high physical strain and emotional stress the teachers were subjected to due to noise. Conclusions. Children and teachers in nursery schools are subjected to high sound levels. Therefore, the education and early sensitization of children to noise in order to prevent prospective hearing damage, e.g. using the noise light, should be set as a goal. Soundproofing measures are also possible. Further investigations to assess the effects of these measures are planned