Determination of the numerical density of perforated synapses in rat neocortex

Summary The numerical density and frequency of perforated synapses in the molecular layer of rat parietal cortex have been determined using 4 procedures in an attempt to overcome problems associated with the size and complex three-dimensional shape of perforated synapses. The following procedures were compared: A, single-section analysis; B, adjacent-section analysis; C, semi-serial-section analysis; and D, complete serial-section analysis. All procedures made use of an unbiased counting rule.Estimates of the numerical density of perforated synapses ranged from 0.06 to 0.27×10⁹ mm^-3, and that of all synapses (non-perforated and perforated) from 1.88 to 2.50×10⁹ mm^-3. The frequency of perforated synapses varied from 4.5 to 18.0%. Procedures B (adjacent-section analysis) and D (complete serial-section analysis), neither of which utilize assumptions regarding the shape of synapses, produced comparable results (numerical density of perforated synapses 0.19–0.27×10⁹ mm^-3, and of all synapses 2.24–2.45×10⁹ mm^-3; frequency of perforated synapses 8.6–10.9%). The frequency of perforated synapses appeared to be underestimated by procedure A (single section analysis; 4.5%) and overestimated by C (semi-serial section analysis; 18%).It is concluded that adjacent-section analysis is the most efficient and effective procedure for determining the numerical density and frequency of complex particles, such as perforated synapses. There is, however, no significant difference in the performance of this procedure compared with that of single-section analysis, for determining the numerical density of synapses in general. Nevertheless, inherent problems of bias within the single-section procedure make the adjacent section method the procedure of choice.     

Frequent gain and loss of pyrrolizidine alkaloids in the evolution of Senecio section Jacobaea (Asteraceae)

Pyrrolizidine alkaloids (PAs) of the macrocyclic senecionine type are secondary metabolites characteristic for most species of the genus Senecio (Asteraceae). These PAs are deterrent and toxic to most vertebrates and insects and provide plants with a chemical defense against herbivores. We studied the PA composition of 24 out of 26 species of Senecio section Jacobaea using GC-MS. The PA profiles of eight of these species have not been studied before and additional PAs were identified for most other species that were included in previous studies. With one exception (senecivernine) all 26 PAs identified in sect. Jacobaea can be regarded as derivatives of the biosynthetic backbone structure senecionine. Based on the PA profiles of the species of sect. Jacobaea and the results of previous tracer studies, we constructed two hypothetical biosynthetic scenarios of senecionine diversification. Both scenarios contain two major reactions: the conversion of the necine base moiety retronecine into the otonecine moiety and site-specific epoxidations within the necic acid moiety. Further reactions are site-specific hydroxylations, sometimes followed by O-acetylations, site-specific dehydrogenations, E, Z-isomerizations, and epoxide hydrolysis and chlorolysis. The GC-MS data and both biosynthetic scenarios were subsequently used to study the evolution of PA formation in sect. Jacobaea by reconstructing the evolutionary history of qualitative PA variation in this section. This was achieved by optimizing additive presence/absence data of PAs and types of enzymatic conversions on a maximum parsimony cladogram of section Jacobaea inferred from DNA sequence and morphological data. Besides showing large intra- and interspecific variation, PA distribution appears to be largely incidental within the whole clade. These results together with the finding that all but one of the PAs identified in sect. Jacobaea are also present in species of other sections of Senecio indicate that differences in PA profiles in Senecio can not be explained by the gain and loss of PA specific genes, but rather by a transient switch-off and switch-on of the expression of genes encoding PA pathway-specific enzymes.     

Depth distribution of adults and immatures of twoTribolium Castaneum strains in pure and mixed cultures

1. The distribution of adults and immatures of two Tribolium castaneum strains in plexiglas towers was studied both in single-strain and in mixed cultures.
2. The adults of the + + strain tended to be, on the average, deeper in the flour than the bb adults, in pure and in mixed cultures.
3. Adult distribution was independent of sex.
4. The correlation between adult and egg distribution was usually negative, due to either adult movement in the flour, or to reduced fecundity and increased cannibalism of eggs where adults were numerous, or both.
5. Larvae, and especially pupae, of bb were more abundant in the upper sections, and + + in the lower sections, of towers, both in pure and in mixed cultures and, in particular, at the higher density.
6. In general, the distribution of the strains in the mixed cultures was very similar to the pure cultures, showing a very small effect of the interaction between the two strains, in comparison with GHENT’S results with two species. It seems that the two strains are very much alike in their ability to exploit their environment and therefore their success is the same (when pupal cannibalism is reduced) whether the biological component of the environment is composed of one or two strains.

     

The effect of beta-endorphin on natural cytotoxicity and antibody dependent cellular cytotoxicity

The ability of the central nervous system to modulate immune responsiveness has received increasing attention. A potential mechanism that would allow the central nervous system to alter the immune system is the release of neuroendocrine and neurotransmitter polypeptides into the peripheral circulation with subsequent modulation of immunocyte function. In this report, we demonstrate that the neuropeptide, beta-[D-ALA2]-endorphin augments natural cytotoxicity but does not effect antibody-dependent cellular cytotoxicity. The observations are discussed in relation to the mechanisms for natural cytotoxicity and antibody dependent cellular cytotoxicity.     

Antibody to immunoselected L-cell antigens mimics stimulating activity of antibody to whole L cells

A heterogeneous IgG antibody raised in rabbits in response to injections of whole L cells was used to identify and select relevant antigens in a nonionic detergent extract of L cells prelabeled with [35S]methionine by means of immunoprecipitation and immunoaffinity chromatography. When analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the immunoprecipitate and immunoeluate contained far fewer protein bands than the whole cell extract but selectively retained a 42,000-MW protein species. In response to injections of the immunoprecipitate, rabbits produced a new antiserum which reacted predominantly with the 42,000-MW protein when reacted with L-cell proteins separated by sodium dodecyl sulfate-gel electrophoresis and transferred to nitrocellulose paper by the Western blot technique. The new antiserum (raised to the immunoprecipitate) and the original antiserum (raised to whole cells) were equipotent in stimulating calcium transport, phospholipid metabolism, and DNA synthesis in L cells. Binding of the IgG fractions of the two antisera displayed identical high affinity binding to L-cell surface antigens, with the same average association constant of 1.5 X 10(6) M-1. These studies have shown that an antiserum raised to whole L cells has a much narrower reactive spectrum with L-cell membrane antigens than might be imagined and has identified a 42,000-MW membrane protein as an important immunogen which itself elicits a potent immune response resulting in an antibody capable of mimicking the cell stimulatory properties of the original antiserum.     

Histamine-releasing activity. IV. Molecular heterogeneity of the activity from stimulated human thoracic duct lymphocytes

Previous studies with the lymphokine, histamine-releasing activity (HRA), showed that HRA consisted of a heterogeneous group of molecules. The possibility of using thoracic duct lymphocytes (TDL) as a source of large quantities of HRA has been investigated. Antigen-stimulated TDL synthesize and release HRA in quantities similar to an equivalent number of peripheral blood lymphocytes (PBL). Streptokinase (SK) antigen routinely caused TDL to produce HRA approximately 15,000 Da. In contrast, staphylococcus enterotoxin B (SEB) induced the formation of a heterogeneous mixture of HRAs with apparent molecular weights of 50,000 and 15,000. Two peaks of activity (HRA I and II) were recovered when the supernatant from SK-stimulated TDL was subjected to ion-exchange chromatography. Interestingly, basophil chemotactic activity (BCA) was also eluted in these two peaks. Although interferon (IFN) is also released by antigen-stimulated TDL, the nonidentity of IFN and HRA was established by fundamental differences in chromatographic properties and specific antisera to IFN. In contrast, these studies suggest that HRA and BCA may be present on the same molecular entity.     

Histamine-releasing activity. V. Characterization and purification using high-performance liquid chromatography

The production of large quantities of the lymphokine(s) histamine-releasing activity (HRA) and its partial purification by Sephadex G-75 and ion-exchange chromatography on carboxymethyl (CM) Sepharose 6B have been detailed (M. A. Lett-Brown, D. O. Thueson, D. E. Plank, M. P. Langford, and J. A. Grant, Cell. Immunol. 87, 434-444, 1984). Two peaks of activity (HRA I and II) were recovered. Preparations of HRA have now been analyzed by high-performance liquid chromatography (HPLC). Thoracic duct lymphocytes stimulated with 200 U/ml streptokinase were used as a source of HRA. Gel-filtration HPLC on a TSK 3000 column separated HRA into two peaks of activity (10,000-20,000 and 1300 Da). Reverse-phase high-performance liquid chromatography using a Nucleosil C-8 column showed that HRA II (the activity eluted at a conductivity of 18-20 mmho on the CM-Sepharose column) eluted as a single sharp peak, the main protein contaminant being cytochrome c, the carrier protein added to enhance the yield of HRA. High-performance liquid chromatography was found to be a useful analytical tool and may be suitable for the large-scale purification of HRA.     

Behavioral stress decreases plasma oxytocin concentrations in primates

Using rhesus monkeys, we studied the effects of a behavioral stress on plasma concentrations of adrenocorticotropin, oxytocin, and vasopressin. The stress resulted in significant increases in adrenocorticotropin and significant decreases in oxytocin concentrations. No significant changes were seen in vasopressin concentrations. To further explore the relationship between plasma oxytocin and pituitary-adrenal function, dexamethasone was administered to rhesus monkeys. This resulted in significant increases in plasma oxytocin concentrations, while adrenocorticotropin decreased.     

改良革兰染色法在显示石蜡切片真菌中的应用

目的建立真菌的病理切片改良革兰染色法。方法选取确诊真菌感染的组织蜡块,切若干空白片,通过苏木素-伊红染色（HE）、高碘酸-无色品红染色（PAS）、六胺银染色（GMS）、改良革兰染色后,比较改良革兰染色法的染色效果。结果改良革兰染色法的染色效果好,该法具有易操作、染色效果稳定等优点。结论改良革兰染色法能够清晰地显示出组织切片中的真菌,并且染色效果稳定,在检测组织中的真菌时可发挥重要的辅助诊断价值,具有广泛的应用前景。     

新疆乌鲁木齐郝家沟剖面郝家沟组和八道湾组孢粉组合及地层意义

作者系统研究了新疆乌鲁木齐郝家沟剖面郝家沟组、八道湾组的孢粉化石,共计98属300种(包括2新属4新种)。根据孢粉属种组成及其含量的变化,自下而上分为5套组合:1.Concavisporites-Dictyophyllidites-Chas-matosporites-Cycadopites组合(组合1),2.Cyathidites-Deltoidospora-Chasmatosporites-Cycadopites组合(组合2),3.Cyathidites-Brevilaesuraspora-Chasmatosporites-Cycadopites-Perinopollenites组合(组合3),4.Cyathidi-tes-Osmundacidites-Pinuspollenites-Piceites-Perinopollenites组合(组合4),5.Cyathidites-Contignisporites组合(组合5)。依据组合中一些重要分子的地质时限讨论及其与相关组合的对比,将组合1归为晚三叠世,组合2—组合4归为早侏罗世早期,组合5归为早侏罗世晚期。并讨论了三叠系与侏罗系的界线及八道湾组的地质时代问题。文中描述孢子花粉2新属4新种,图示孢子花粉及疑源类共74属175种。