Application of morphometric methods to the cytologic study of intradermal nevi.

Twenty-one intradermal nevi were studied by morphometric methods in an attempt to morphologically characterize the two types of nevus cell--epithelioids, type A, and fusiforms, type C--and to quantify the differences between them. Morphometric parameters of the intradermal nevi were compared with similar parameters of melanocytes and melanoma cells so that the maturation rates of the nevi cells could be established and to see if the parameters might indicate the degree of malignancy. Superficial nevus cells were differentiated from deep cells by their larger size and larger nuclear area. Nuclear area appeared to have potential for differentiating benign from malignant tumors. Decrease in cellular area appeared to indicate maturation rather than atrophy. Melanoma cells were differentiated by their larger size. Cell nuclear perimeter appeared to have confirmatory value, while cell perimeter was inconclusive.     

Urinary excretion of digoxin-like immunoreactive factor and arginine-vasopressin in rats after several osmotic loads

Urinary digoxin-like immunoreactive factor (DLIF), arginine-vasopressin (AVP) and other urinary parameters were investigated under normal conditions and after the i.p. injection of the following solutions: distilled water, isotonic and hypertonic NaCl, NaHCO3, KCl and urea, at a rate of 3 ml/100 g body weight. The measurement of digoxin-like immunoreactivity by two different radioimmunoassays showed that DLIF was stimulated by all volume loads regardless of the presence or absence of osmolar compounds. This dissociation between DLIF and urinary sodium excretion suggests that DLIF may not constitute the natriuretic hormone. Moreover, a dissociation between DLIF and AVP excretion also were found, which speaks against the hypothesis of a common mechanism of stimulation for both substances.     

A Comparison of the Efficacy of Nuclear Polyhedrosis and Granulosis Viruses in Spray and Bait Formulations for the Control of Agrotis segetum (Lepidoptera: Noctuidae) in Maize

Agrotis segetum nuclear polyhedrosis virus (AsNPV) and granulosis virus (AsGV), propagated in laboratory cultures of A. segetum in England and A. ipsilon in Spain, respectively, were applied to plots of maize plants at the one‐ to four‐leaf stage of growth. Plots were arranged in a 6 x 6 Latin square design and infested with second‐instar A. segetum larvae (the common cutworm). Each virus was applied in separate treatments by two application methods; as an aqueous spray containing 0.1% Agral as a wetting agent, and as a bran bait. The NPV was applied at a rate of 4 X 10¹² polyhedra/ha, and the GV at 4 X 10¹³ granules/ha. Soil and plants were sampled for larvae on three occasions following virus treatment: 24 h, 4 days and 11 days. The larvae were reared on diet in the laboratory, until death or pupation, to examine the rate and level of viral infection. Infection data showed 87.5% and 91% NPV infection and 12.5% and 55% GV infection in spray and bait treatments, respectively, in larvae sampled 24 h after treatment. In larvae sampled 4 days after treatment, the results were 78% and 100% NPV infection, and 13% and 6% GV infection. A total of only six larvae were retrieved on day 11. In both treatments larvae infected with AsNPV died significantly more rapidly and at an earlier instar than those infected with AsGV, indicating that AsNPV appears to have better potential as a control agent for A. segetum.     

Sea urchin sperm head plasma membranes: characteristics and egg jelly induced Ca2+ and Na+ uptake

Sea urchin sperm respond to egg factors with changes in the ionic permeability of their plasma membrane. It has been previously shown that plasma membranes isolated preferentially from sea urchin sperm flagella respond to egg jelly increasing their Ca2+ and Na+ uptake (Darszon et al. (1984) Eur. J. Biochem. 144, 515-522). However, the egg jelly induced acrosome reaction occurs in the sperm head, and there is evidence for an heterogeneous distribution of plasma membrane components within the various regions of this cell. We here report a method for purifying sperm head membranes using positively charged beads according to Jacobson (1977) Biochim. Biophys. Acta 471, 331-335). Under the transmission electron microscope these membranes appeared homogeneous and apparently free of internal membranes. The yield of the preparation was 0.9% of the total protein in the sperm homogenate. The preparation contained less than 5% of the mitochondrial marker cytochrome oxidase, and 10% of the total DNA/mg protein. Surface labeling with 125I indicated a 2.5-3-fold enrichment in specific activity of the head membranes with respect to whole sperm. The SDS band pattern and the lipid composition of this preparation were different from those of isolated flagellar membranes. Phosphatidylcholine was higher in the head membranes, while phosphatidylserine and phosphatidylethanolamine were lower. The head membranes displayed a 1.7-2.3-fold higher Ca2+-ATPase activity and a 2.5-fold lower Na+/K+-ATPase activity, than the flagellar membranes. These results are consistent with a heterogeneous distribution of membrane components along the sea urchin sperm plasma membranes. Isolated head membranes sonicated in the presence of soybean phospholipid liposomes responded to egg jelly with a species-specific increase in Ca2+ and Na+ uptake. As in whole sperm, Ca2+ uptake was inhibited by the Ca2+ channel blocker nisoldipine. A close analog of this compound, [3H]nitrendipine, binds with high affinity to head membranes in a saturable, reversible manner, showing a Kd and Bmax of 31 nM and 5.3 pmol/mg protein, respectively.     

Flow cytometric analysis of the effects of high protein diet on isolated rat liver mitochondria

We have investigated changes that occur in mitochondria obtained from the livers of rats that had been maintained on a high protein diet (80% casein instead of 20%) for 6 months. Liver homogenates were separated by centrifugation into a mitochondrial fraction, a nuclear fraction and the supernatant fluid of the nuclear fraction (nuclear wash). Rhodamine-123 was used to selectively stain mitochondria depending upon their membrane potential. The stained organelles were processed through a flow cytometer where the fluorescent stains were excited by the 488 nm wavelength of a laser and the resultant fluorescence signals analysed. After 6 months on a high protein diet, mitochondria displayed an increase in the fluorescence associated with rhodamine-123 uptake in both mitochondrial and nuclear wash fractions, while mitochondrial fluorescence in the nuclear fraction showed a heterogeneous distribution. This was interpreted as an increase in membrane potential in most of the liver mitochondria under these nutritional conditions, with a certain degree of heterogeneity. These functional changes may be correlated with morphological alterations previously reported and show the usefulness of flow cytometry for biochemical analysis of isolated mitochondria.     

The molecular organization of nerve membranes

Summary The lipid content and composition from an axolemma-rich preparation isolated from squid retinal axons was analyzed.The lipids, which accounted for 45.5% of the dry weight of this membrane, were composed of 22% cholesterol, 66.7% phospholipids and 5.2% free fatty acids. The negatively charged species phosphatidyl ethanolamine (37%), phosphatidyl serine (10%) and lysophosphatidyl ethanolamine (4%) made up 51% of the phospholipids. The amphoteric phosphatidyl choline and sphingomyelin accounted for 39% and 4%, respectively.The relative distribution of fatty acids in each of the isolated phospholipids was studied. The most remarkable feature of these phospholipids was the large proportion of long-chain polyunsaturated fatty acids. The 226 acyl chain accounted for 37% in phosphatidyl ethanolamine, 21.7% in phosphatidyl choline, 17.5% on phosphatidyl serine and 20.3% in sphingomyelin (all expressed as area %).The molar fraction of unsaturated fatty acids reached 65% in phosphatidyl ethanolamine and 42.0 and 44.8% in phosphatidyl choline and phosphatidyl serine, respectively. The double bond index in these species varied between 1.0 and 2.6.The lipid composition of the axolemma-rich preparation isolated from squid retinal axons appears to be similar to other excitable plasma membranes in two important features: (a) a low cholesterol/phospholipid molar ratio of 0.61; and (b) the polyunsaturated nature of the fatty acid of their phospholipids.This particular chemical composition may contribute a great deal to the molecular unstability of excitable membranes.The preceding papers of this series were published inArchives of Biochemistry and Biophysics.     

Competition between laboratory populations of green leafhoppers,Nephotettix spp. (Homoptera: Cicadellidae)

Intra- and interspecific competition between laboratory populations of four green leafhoppers, Nephotettix spp. was studied in the laboratory under three different temperature regimes of 24°C, 27°C and 30°C. For the single-species population of the three tropical species, the equilibrium density increased as the temperature increased. On the other hand, for the temperature species N. cincticeps, the highest equilibrium density was at the intermediate temperature and the lowest at high temperature. Interspecific interactions between two tropical (N. virescens vs. N. nigropictus), a tropical and a temperature (N. virescens vs. N. cincticeps) and a rice-feeding and a grass-inhabiting (N. virescens vs. N. malayanus) Nephotettix species were also studied in the laboratory at the three temperature regimes. Temperature differentially affected the outcome of competition between two Nephotettix species. Between N. virescens and N. nigropictus, the latter was more successful over the former at low and intermediate temperatures, while the former was more successful at high temperature. Between N. virescens and N. cincticeps, the temperate species inhibited the growth of the tropical species at low temperature while the tropical species inhibited the growth of the temperate species at high temperature. At intermediate temperature, the population of N. virescens persisted at a slightly higher density over the population of N. cincticeps. Between the rice-feeding N. virescens and the grass-inhabiting N. malayanus, regardless of temperature the population density of the latter was greatly reduced and later became extinct while the population of the former continued its growth. These consequences of competition between two Nephotettix species conformed fairly well to those predicted by theLotka-Volterra model using demographic parameters specified for each species.     

Order-disorder phenomena in myelinated nerve sheaths. II. The structure of myelin in native and swollen rat sciatic nerves and in the course of myelinogenesis

The algorithm described in the accompanying paper was applied to X-ray scattering experiments performed with rat sciatic nerves, either as a function of the age of the animal (4 to 30 days), or with adult nerves swollen in non-isotonic media. The results were all consistent with the model of disorder used in the theoretical treatment. The algorithm leads, in one step, from the data to the numerical values of the parameters, avoiding all intermediate manipulation. For each experiment a variety of parameters was determined: the average D and the variance sigma 2D of the repeat distance, the average number [N] of motifs per crystallite, the set [idiff(h/D)], which defines the diffuse scattering, the fraction alphaloose of myelin that does not belong to the compact sheaths, and the set [imotif (k/2D)], which suffices to define the continuous intensity curve of the motif imotif(s). Note the remarkable wealth of information, especially by contrast with conventional analyses which, as a rule, only yield the values of D and of the set [imotif(h/D)] (insufficient to determine the function imotif(s]. The function imotif(s) and the parameters D and sigma D (and thus the local structure of the myelin sheaths) were shown to be almost invariant in the course of myelinogenesis; what varies is mainly the total amount of myelin in the nerve and the number of membranes per sheath. Swelling agents have a dramatic influence on the X-ray scattering spectra, but in spite of the conspicuous variation of D, sigma D and [N] the structure of the motif is invariant. The structure of the motif was shown to be quite different in the native and in the swollen samples; the stacking disorder appears to involve mainly the cytoplasmic space in native myelin, the external space in swollen nerves. The very notion of electron density profile, when disorder is present, is discussed. Two criteria were proposed to select the "best" signs of the reflections: two sets came out at almost the same rank, one corresponding to Caspar & Kirschner's the other to Worthington & McIntosh's proposals, neither of which can be ruled out according to the criteria used in this work.