Qualitative and quantitative analysis of glycine- and GABA-immunoreactive nerve terminals on motoneuron cell bodies in the cat spinal cord: A postembedding electron microscopic study

The distribution of glycine- and gamma-aminobutyric acid (GABA)-like immunoreactivity (LI) in nerve terminals on the cell soma of motoneurons in the aldehyde-fixed cat L7 spinal cord was examined using postembedding immunogold histochemistry in serial ultrathin sections. Quantitative examination of 405 terminals on eight neurons of α-motoneuron size in the L7 motor nuclei from one animal was performed. A majority of the terminals (69%) were immunoreactive to glycine and/or GABA. These terminals contained flat or oval synaptic vesicles, thus classifying them as F type or as C type in one case. In no case was a type-F terminal unlabeled for both glycine and GABA. Most of the immunolabeled terminals were immunoreactive to glycine only (62.5%), whereas 35.4% contained both glycine- and GABA-LI. A very small number of immunolabeled terminals (2%) were immunoreactive to GABA only. In those terminals, where glycine- and GABA-LI coexisted, the gold particle density for each amino acid was only half of that seen in boutons containing only one of the two amino acids. The involvement of glycine and GABA in postsynaptic inhibition of spinal α-motoneurons is discussed, with particular reference to the possibility that these two inhibitory amino acids may be coreleased from a significant proportion of the nerve terminals impinging on the cell bodies. © 1996 Wiley-Liss, Inc.     

Cancer in offspring of parents engaged in agricultural activities in Norway: Incidence and risk factors in the farm environment

In this study of cancer in offspring we demonstrate that factors linked to horticulture and use of pesticides are associated with cancer at an early age, whereas factors in animal husbandry, in particular poultry farming, are associated with cancers in later childhood and young adulthood. Incident cancer was investigated in offspring born in 1952–1991, to parents identified as farm holders in agricultural censuses in Norway in 1969–1989. In the follow-up of 323,292 offspring for 5.7 million person-years, 1,275 incident cancers were identified in the Cancer Registry for 1965–1991. The standardized incidence for all cancers was equal to the total rural population of Norway, but cohort subjects had an excess incidence of nervous-system tumours and testicular cancers in certain regions and strata of time that could imply that specific risk factors were of importance. Classification of exposure indicators was based on information given at the agricultural censuses. Risk factors were found for brain tumours, in particular non-astrocytic neuroepithelial tumours: for all ages, pig farming tripled the risk [rate ratio (RR), 3.11; 95% confidence interval (CI), 1.89–5.13]; indicators of pesticide use had an independent effect of the same magnitude in a dose-response fashion, strongest in children aged 0 to 14 years (RR, 3.37; 95% CI, 1.63–6.94). Horticulture and pesticide indicators were associated with all cancers at ages 0 to 4 years, Wilms' tumour, non-Hodgkin's lymphoma, eye cancer and neuroblastoma. Chicken farming was associated with some common cancers of adolescence, and was strongest for osteosarcoma and mixed cellular type of Hodgkin's disease. The main problem in this large cohort study is the crude exposure indicators available; the resulting misclassification is likely to bias any true association towards unity. © 1996 Wiley-Liss, Inc.     

Temporary loss of perivascular aquaporin-4 in neocortex after transient middle cerebral artery occlusion in mice

The aquaporin-4 (AQP4) pool in the perivascular astrocyte membranes has been shown to be critically involved in the formation and dissolution of brain edema. Cerebral edema is a major cause of morbidity and mortality in stroke. It is therefore essential to know whether the perivascular pool of AQP4 is up- or down-regulated after an ischemic insult, because such changes would determine the time course of edema formation. Here we demonstrate by quantitative immunogold cytochemistry that the ischemic striatum and neocortex show distinct patterns of AQP4 expression in the reperfusion phase after 90 min of middle cerebral artery occlusion. The striatal core displays a loss of perivascular AQP4 at 24 hr of reperfusion with no sign of subsequent recovery. The most affected part of the cortex also exhibits loss of perivascular AQP4. This loss is of magnitude similar to that of the striatal core, but it shows a partial recovery toward 72 hr of reperfusion. By freeze fracture we show that the loss of perivascular AQP4 is associated with the disappearance of the square lattices of particles that normally are distinct features of the perivascular astrocyte membrane. The cortical border zone differs from the central part of the ischemic lesion by showing no loss of perivascular AQP4 at 24 hr of reperfusion but rather a slight increase. These data indicate that the size of the AQP4 pool that controls the exchange of fluid between brain and blood during edema formation and dissolution is subject to large and region-specific changes in the reperfusion phase.     

Morphological and GABA-immunoreactive development of the embryonic chick telencephalon

The development of neurons utilizing γ-aminobutyric acid (GABAergic neurons) in prosencephalon and telencephalon from chicken embryonic days 4–14 (E4–E14) was studied by means of immunohistochemistry. Furthermore, routine histology and transmission electron microscopy, respectively, were performed in order to study the morphological development in the designated area. The main finding is that development of GABAergic neurons in the chick telencephalon is rapid; the GABA neurons are appearing in bulk at day 8, being “overexpressed” at days 10–11, decreasing in numbers thereafter and achieving mature morphology on day 14, which is considerably faster than in the rodent.Morphological analysis revealed that the prosencephalon mainly consisted of a thin layer of undifferentiated neuroblasts in the E4 embryo. By E6, the prosencephalon had increased in thickness and occasional cells outside the neuroepithelium showed a more mature morphology with a few cells weakly staining positive for GABA. At E8, the prospective granular and subventricular layers had developed. At E14, the appearance of the telencephalon is approximating that of the adult since both ependymal cells and morphologically mature neurons can be seen.     

Lung function at 10 yr is not impaired by early childhood lower respiratory tract infections

The causal relationship between lower respiratory tract infections (LRIs) in early life and reduced lung function later in childhood is unsettled. Therefore, we assessed whether LRIs the first 2 yr of life influenced lung function development from birth to school age. In the prospective Oslo birth cohort, ‘the Environment and Childhood Asthma (ECA) study’ lung function was measured at birth in 802 infants by tidal flow volume loops and in 664 infants by passive respiratory mechanics and half yearly questionnaires, including LRI questions, were completed until 2 yr of age. The present study includes 607 children with information about LRIs the first 2 yr of life and successfully forced expiratory flow (FEF) volume measurements at the 10‐yr follow‐up assessment. At 10 yr of age, FEF at 50% of forced vital capacity (FEF₅₀) (mean 95% confidence interval) was reduced in children with at least one bronchiolitis (85.0, 80.6–89.5, p = 0.020) or bronchitis (86.2, 82.6–89.8, p = 0.030) or ≥3 LRIs (83.4, 78.1–88.8, p = 0.017) when compared with no LRIs (90.6, 88.8–92.5) by 2 yr of life. The effects were significant in girls only when stratifying for gender. Among girls with later bronchiolitis compliance of the respiratory system (3.64, 3.17–4.10 vs. 4.18, 3.98–4.37, p = 0.031) and the ratio of time to peak tidal expiratory flow to total expiratory time (t_PTEF/t_E) measured at birth was significantly reduced (0. 26, 0.23–0.29 vs. 0.32, 0.30–0.33, p = 0.005) when compared with children with no LRIs. Change in lung function from birth (by t_PTEF/t_E) to 10 yr of age was not significantly associated with LRIs the first 2 yr of life, and LRIs by 2 yr of life were not significantly associated with lung function at 10 yr of age in regression analyses including lung function at birth and other possible predictors of lung function at 10 yr. In our study, LRIs during the first 2 yr of life did not impair lung function development from birth until 10 yr of age.