Neonatal malnutrition in the rat affects the delivery of sulfatides from microsomes and their entry into myelin

Brain slices from 18 day old normal and malnourished rats were incubated in the presence of [³⁵S]sulfate to explore its incorporation into sulfatides of a total brain homogenate and the appearance of labeled sulfatides in different subcellular fractions. While the incorporation of label into sulfatides of the total homogenate was similar in both groups of animals, in subcellular fractions separated on a linear sucrose density gradient, labeling of sulfatides in malnourished animals was relatively higher in the region corresponding to the microsomal fraction. Time course incorporation and pulse-chase experiments were carried out to explore the kinetics of labeling of microsomal and myelin sulfatides. In pulse-chase experiments, normal controls showed a decrease in the specific radioactivity of sulfatides in the microsomal fraction after the chase, which was not observed in malnourished animals, while the appearance of labeled sulfatides in the myelin fraction of the latter group of animals was found to be lower than in normals. These results suggest that in neonatal malnutrition there is a defect in the transport of de novo synthesized sulfatides towards myelin or/and a problem in the assembly of these lipids into the myelin membrane.     

Mixing patterns in Amazon lakes

The diel mixing patterns of two small floodplain lakes, Lago Jacaretinga in the Amazon drainage, and Lago Cristalino in the Rio Negro system, were investigated during both the high-water and low-water states of the Amazon River hydrograph. Measurements included temperature, oxygen, ammonia, phosphate, and chlorophyll. In both lakes thermal stratification developed during the day and was eroded at night. During the low-water period when the lakes were shallow, nocturnal circulation extended to the lake bottom, whereas when the lakes were deeper (greater than about 5 m), circulation did not reach the bottom and an anoxic hypolimnion developed. During the low-water period, percent of oxygen concentrations were relatively high but always less than saturation. Low oxygen concentrations were observed during the high-water period. At all times nocturnal mixing supplied a significant amount of oxygen to the lake ecosystems. Nighttime upward mixing of recycled nitrogen and phosphorus also appeared to be important nutrient sources for algal productivity.     

High density of transmembrane glycoproteins on the flagellar surface of boar sperm cells

Membrane halves of boar sperm flagella were produced by freeze-fracture and labeled in situ with concanavalin A and wheat germ agglutinin; the lectins were visualized with protein-gold complexes. Concanavalin A and wheat germ agglutinin binding sites partition with both protoplasmic and exoplasmic halves of the membrane. A high density of lectin marking was found on protoplasmic membrane halves; we conclude that the label corresponds to transmembrane glycoproteins that, on freeze-fracture, are dragged across the outer (exoplasmic) half of the phospholipid bilayer. Our demonstration of numerous transmembrane proteins in sperm flagella offers the structural setting for previous models on flagellar surface motility that postulate accessibility of motile membrane components to the submembranous cytoskeleton.     

The innervation of the pyloric region of the crab,Cancer borealis: Homologous muscles in decapod species are differently innervated

Summary The muscles of the pyloric region of the stomach of the crab,Cancer borealis, are innervated by motorneurons found in the stomatogastric ganglion (STG). Electrophysiological recording and stimulating techniques were used to study the detailed pattern of innervation of the pyloric region muscles. Although there are two Pyloric Dilator (PD) motorneurons in lobsters, previous work reported four PD motorneurons in the crab STG (Dando et al. 1974; Hermann 1979a, b). We now find that only two of the crab PD neurons innervate muscles homologous to those innervated by the PD neurons in the lobster,Panulirus interrruptus. The remaining two PD neurons innervate muscles that are innervated by pyloric (PY) neurons inP. interruptus. The innervation patterns of the Lateral Pyloric (LP), Ventricular Dilator (VD), Inferior Cardiac (IC), and PY neurons were also determined and compared with those previously reported in lobsters. Responses of the muscles of the pyloric region to the neurotransmitters, acetylcholine (ACh) and glutamate, were determined by application of exogenous cholinergic agonists and glutamate. The effect of the cholinergic antagonist, curare, on the amplitude of the excitatory junctional potentials (EJPs) evoked by stimulation of the pyloric motor nerves was measured. These experiments suggest that the differences in innervation pattern of the pyloric muscles seen in crab and lobsters are also associated with a change in the neurotransmitter active on these muscles. Possible implications of these findings for phylogenetic relations of decapod crustaceans and for the evolution of neural circuits are discussed.Abbreviations ACh acetylcholine - Carb carbamylcholine - cpv muscles of the cardio-pyloric valve - cpv7n nerve innervating muscle cpv7 - cv muscles of the ventral cardiac ossicles - cv1n nerve innervating muscle cvl - cv2n nerve innervating muscle cv2 - EJP excitatory junctional potential - IC inferior cardiac neuron - IV inferior ventricular neuron - IVN inferior ventricular nerve - LP lateral pyloric neuron - LPG lateral posterior gastric neuron - lvn lateral ventricular nerve - mvn medial ventricular nerve - p muscles of the pylorus - PD pyloric dilator neuron - PD _in intrinsic PD neuron - PD _ex extrinsic PD neuron - pdn pyloric dilator nerve - PY pyloric neuron - pyn pyloric nerve - STG stomatogastric ganglion - VD ventricular dilator neuron     

Kinetics of the 5′-nucleotidase and the adenosine deaminase in subcellular fractions of rat brain

Suspensions of rat brain microsomes, synaptosomes, and synaptic vesicles were able to convert adenosine to inosine by means of adenosine deaminase. Isosbestic points of this transformation, at 222, 250 and 281 nm, remained unchanged with time-course. This fact suggests that adenosine deaminase (ADA, E.C. 3.5.4.4) is located on the surface of the vesicles whereas purine nucleoside phosphorylase (PNP, E.C. 2.1.2.4) is located inside the vesicles. Kinetic parameters of the particulate 5-nucleotidase (5N, E.C. 3.1.3.5) and adenosine deaminase were analogous to those of the cytosolic enzymes. These results suggest that soluble and particulate enzymes represent different pools of the same molecular species.     

Heterogeneous localization of some purine enzymes in subcellular fractions of rat brain and cerebellum

The activity of guanine deaminase (GAH, E.C. 3.5.4.3) was lower in rat cerebellum soluble and microsomal fractions than in rat brain subfractions. Adenosine deaminase (ADA, E.C. 3.5.4.4) activity was released in higher proportion than guanine deaminase, purine nucleoside phosphorylase (PNP, E.C. 2.1.2.4), 5-nucleotidase (5N, E.C. 3.1.3.5), and lactate (LDH, E.C. 1.1.1.27) and malate (MDH, E.C. 1.1.1.37) dehydrogenase in press-juices of rat brain. Furthermore, nerve ending-derived fractions (synaptosomes and synaptic vesicles) showed an enrichment of adenosine deaminase and also of 5-nucleotidase. The action of deoxycholate over the subfractions did not increase the activity of either enzyme. The contrary occurred with the remaining enzymes studied. Thus, it is possible that one set of enzymes are located on the surface of the particulate vesicles, whereas another set are located inside these vesicles, suggesting a compartmentation of purine catabolic enzymes in different areas of the central nervous system.     

Heterogeneity of Benzodiazepine Receptors: Experimental Differences Between [3H]Flunitrazepam and [3H]Ethyl-β-carboline-3-carboxylate Binding Sites in Rat Brain Membranes

Abstract: This study was designed to analyze possible differences in the binding of [³H]flunitrazepam ([³H]FNZP) and [³H]ethyl - β - carboline - 3 - carboxylate ([³H]β-CCE), to rat brain membranes, in various experimental conditions. In cerebral cortex, hippocampus, cerebellum, and orain stem the number of binding sites for [³H]β-CCE was higher than for [³H]FNZP; both were displaced by clonazepam. Until the 7th day of postnatal brain development the numbers of [³H]FNZP and [³H]β-CCE sites were equivalent; but later on, the β-carboline sites increased to a higher level. Noradrenergic denervation by 6-hydroxydopamine was followed in the hippocampal formation. Already after 2 days, there was a decrease in [³H]FNZP sites, which reached 70% of control after 14 days. Similar results were obtained with DSP-4 denervation. This change was only in B_max and not in K_D, In contrast, the [³H]β-CCE sites did not change with denervation. Neonatal injection of l - 2,4,5 - trihydroxyphenylalamine or DSP-4 produced in the adult a decrease in [³H]FNZP sites in the cerebral cortex, in parallel with the noradrenergic denervation. On the other hand, there was an increase in the cerebellum and brain stem, in correspondence with the hyperinnervation by sprouting. In these rats, the number of sites for [³H]β-CCE did not change in the different brain regions. With 0.1% Triton X-100, applied to synaptosomal membranes, [³H]FNZP binding was reduced by 35%, while that of [³H]β-CCE was not significantly changed. These results suggest that there is heterogeneity of binding sites for benzodiazepine receptors in rat brain. A tentative interpretation of the experiments involving noradrenergic denervation and hyperinnervation, as well as those with Triton X-100, is that [³H]FNZP binds to pre- and postsynaptic receptors, while [³H]β-CCE binds mainly to postsynaptic benzodiazepine receptors.     

Development of a homologous radioimmunoassay for secreted hamster prolactin

A specific and sensitive homologous radioimmunoassay has been developed for secreted hamster prolactin. Hamster serum and pituitary extracts showed parallel dilution-response curves with hamster prolactin. The sensitivity of the assay ranged from 0.5 to 1.0 ng/ml, and the intra- and inter-assay coefficients of variation were 6 and 10%, respectively. Additionally we have demonstrated that the rat prolactin radioimmunoassay kit distributed by the National Institute of Arthritis, Metabolism, and Digestive Diseases is an inadequate method for the measurement of hamster prolactin.     

Thermodynamic approach to biomass distribution in ecological systems

In the derivation of the biomass distribution function for an ecological population critical use is made of an energetic constraint on the maximization of biomass diversity. The nature of this constraint is explored in detail using Kleiber's relation σ(m)=cm ^γ between animal metabolic rate σ(m) and body weightm in conjuction with the Prigogine-Wiame thermodynamic paradigm for specific entropy production in biological stationary states. These two inputs fix the energetic constraint on the maximization of biomass diversity to be the constancy of the mean metabolic rate of the ecosystem. The resulting biomass distribution function is tested against observational data.