Development of resistance to lead encephalopathy during maturation in the rat pup

The purpose of this study was to determine the maturational period during which the rat pup becomes resistant to the toxic effects of lead on the brain. Pups were fed lead, as lead acetate, by esophageal catheter for 14 days beginning at various ages between 14-24 days. The daily lead doses, which produced a hemorrhagic cerebellar encephalopathy in at least 50% of pups, were 400 micrograms Pb/g body weight for animals fed from 14 days of age, 800 micrograms/g for animals fed from 16 days, and 1600 micrograms/g for animals fed from 18 days. In contrast, pups fed even higher lead doses beginning at 20 days showed only a patchy cerebellar edema by light microscopy while pups fed from 24 days had normal cerebellums by light microscopy. The encephalopathic lead doses in the younger pups resulted in the same cerebellar lead concentrations (about 30 micrograms/g protein) as the higher lead doses fed pups beginning at 20 ot 24 days. When corrected for blood lead concentrations, the cerebellar lead concentrations were 20-25% higher in the encephalopathic compared to the older encephalopathy-resistant animals. This difference may be accounted for by cerebellar hemorrhages in the younger animals. Polarographic studies showed inhibition of respiration in cerebellar slices from animals fed lead from 14 days of age but not in animals fed from 20 or 24 days of age. Our results that, during the encephalopathy-sensitive age period, a critical cerebellar concentration of lead is associated with the encephalopathy. Resistance to lead encephalopathy in older animals, with similar cerebellar lead concentrations, may be related to a capacity to sequester lead in new cellular locations away from its site of action on aerobic energy metabolism.

Rat cerebral cortical slice respiration in media of various osmolarities

Freshly separated immature (5-day-old) and mature (60-day-old) rat cerebral cortical tissue demonstrates a Na+-dependent respiratory component similar to that recently described in primary cultured astrocytes. This respiratory component, which is not coupled to oxidative phosphorylation, increases as the osmolarity is increased above 354 mOsm in media with NaCl as the osmotic agent. With decreasing osmolarity from 354 to 80 mOsm, this respiratory component decreases more in cortical tissue than in cultured astrocytes. We propose that the respiratory response of neurons to decreasing extracellular osmolarity may differ from that of astrocytes in situ.

Cell volume regulation in the proximal convoluted tubule

To evaluate the effect of hyper- and hypotonicity on proximal convoluted tubule (PCT) cell volume, nonperfused PCT were studied in vitro with hypertonic solutions containing sodium chloride, urea, or mannitol (450 mosmol/kg H2O) and with hypotonic low sodium chloride solutions (160 mosmol/kg H2O). When the tubules were subjected to hypertonic peritubular solutions containing NaCl, cell volume immediately decreased by 15.5% and remained constant throughout the experimental period (60 min). With mannitol, the initial decrease was identical to that with NaCl (17.7%), but the PCT volume increased slightly during the experimental period. With urea, the decrease in cell volume was smaller (7%) and transient. In hypotonicity, the PCT swelled rapidly, but this swelling was followed by a rapid regulatory phase in which PCT volume nearly returned to control values after less than 10 min. With a potassium-free peritubular medium or 10(-3) M ouabain, the regulatory phase of hypotonicity completely disappeared, whereas the cells did not maintain their reduced volume in NaCl-induced hypertonicity. These results suggest that Na-K-ATPase plays an important role in the maintenance of a reduced cellular volume in hypertonicity and in the regulatory phase of hypotonicity, probably by an active extrusion of sodium and water from the cell.

[The muscular atrioventricular septum]

On the left ventricle septal wall, the tricuspid valve ring attachment is displaced forward, towards the cardiac apex. To this trapezoïdal area between the two atrio-ventricular annuli, the medial wall of the right atrium is attached (laminar attachment), resulting in a atrio-ventricular septum which is: --membranous at its superior extremity (membranous atrio-ventricular septum well described in all classical anatomy textbooks); --and muscular at its inferior extremity. Located in the inferior anterior portion of the Koch triangle, the muscular atrio-ventricular septum is roughly triangular in shape. Its superior and anterior borders are well delineated and represented by: --the pars muscularis crest, at its junction with the membranous atrio-ventricular septum; --and the insertion of the tricuspid septal leaflet on this pars muscularis of the inter-ventricular septum. On the contrary, its third border, the posterior inferior left, is not well defined and varies greatly with the amount of fat filling the crux of the heart. The atrio-ventricular septum separates the right atrium from the base of the left ventricle outflow tract. It shares the important relationship of the "carrefour" of the four cardiac chambers (7 - 8) and first of all the conduction system and its vascular supply. The concept of an atrio-ventricular septum, both muscular and membranous, is to be kept in mind for the good understanding and the surgical correction of different types of "common atrio-ventricular canal" (2 - 10).

In vitro cellular respiration at elevated temperatures in developing rat cerebral cortex

Cellular respiration in vitro was studied in cerebral cortical tissue from rats 2-60 days of age. Respiration was measured polarographically over the temperature range 34-44 degrees C in tissue slices in a basal condition; maximally stimulated by an uncoupler of oxidative phosphorylation, dinitrophenol; and inhibited by a blocker of mitochondrial oxidative phosphorylation, oligomycin. Basal respiration at 34 degrees C increased about 80% between 7 and 30 days of age. Oligomycin-insensitive respiration did not change with age. Dinitrophenol-stimulated respiration was unchanged from 2 to 10 days and then increased over 100% between 10 and 15 days of age. The Q10 for dinitrophenol-stimulated respiration increased from a value of 1 in tissue from rats 2-10 days of age to about 2 in tissue from rats 15 days and older. Our results confirm the previously reported maturational increases in basal respiration and in respiratory capacity in rat cerebral cortical tissue. The maturational increase in maximal respiratory capacity occurs in a short age interval coincident with a marked increase in the Q10 for the hyperthermic temperature range. Both these properties may be important in the increasing resistance to hyperthermia-induced seizures and their functional sequelae in the rat pup.

Maturation of potassium-stimulated respiration in rat cerebral cortical slices

Maximal dinitrophenol-stimulated respiration and K+-stimulated respiration were measured polarographically in cerebral cortical slices taken from rats aged 2-60 days. Increasing K+ concentrations produced an increase in respiration in slices from animals aged 15 days and older, but not in slices from animals aged 10 days and younger. Dinitrophenol-stimulated respiration, or the maximal respiratory capacity of the tissue, showed a similar increase between 10 and 15 days of age. At each age the maximal respiratory capacity was 6-8 ng at 0/mg protein min greater than the maximal K+-stimulated respiration.

A comparative trial of home and hospital psychiatric treatment: financial costs

The financial costs of community-based treatment, stressing home treatment, were compared with the cost of hospital-based treatment during one year. Of 155 patients destined to receive inpatient treatment, 76 were randomly assigned to home treatment, 79 to hospital treatment; the two groups were similar as to important social, demographic, and clinical characteristics. The principal differences between the two treatments concerned the focus of treatment, the locale of treatment, the degree to which continuity of treatment was maintained, and the roles of the respective treatment staffs. Manpower and operating costs, measured in dollars, were estimated in two ways. Either way, hospital-based treatment was more expensive during the year: 64.1% more expensive (+3,250 vs. +1,980 per patient) in the first instance, 108.9% more expensive (+6,750 vs. +3,230 per patient) in the second. With two exceptions during the first month of treatment, the proportions of patients and families receiving either treatment who incurred other costs of treatment were low, and the differences between groups were not significantly different. A higher proportion of patients and families receiving home-based treatment defrayed the cost of the patient's psychotropic drugs; second, a higher proportion of families of patients receiving hospital-based treatment defrayed transportation costs. The proportions of patients and families incurring costs of the consequences of illness were low, and the differences between treatment groups were not significant. We compared this study with similar studies, discussed the generalizability of the results of this study and similar studies, and identified issues for future research.