Can we determine the biological availability of sediment-bound trace elements?

It is clear from available data that the susceptibility of biological communities to trace element contamination differs among aquatic environments. One important reason is that the bioavailability of metals in sediments appears to be altered by variations in sediment geochemistry. However, methods for explaining or predicting the effect of sediment geochemistry upon metal bioavailability are poorly developed. Experimental studies demonstrate that ingestion of sediments and uptake from solution may both be important pathways of metal bioaccumulation in deposit/detritus feeding species. Relative importance between the two is geochemistry dependent. Geochemical characteristics of sediments also affect metal concentrations in the tissues of organisms collected from nature, but the specific mechanisms by which these characteristics influence metal bioavailability have not been rigorously demonstrated. Several prerequisites are necessary to better understand the processes that control metal bioavailability from sediments. 1) improved computational or analytical methods for analyzing distribution of metals among components of the sediments; 2) improved computational methods for assessing the influences of metal form in sediments on sediment-water metal exchange; and 3) a better understanding of the processes controlling bioaccumulation of metals from solution and food by metazoan species directly exposed to the sediments. Such capabilities would allow mechanistic explanations essential to the development of practical tools sought for determining sediment quality criteria for metals.     

New antifungal agents for the systemic mycoses

The azoles are the prominent broad spectrum oral antifungal agents in use or under clinical investigation for the systemic mycoses. This class of antifungal agents is represented by the marketed drug ketoconazole (Nizoral) and the experimental triazoles furthest along in clinical trials in the United States, itraconazole and fluconazole. Ketoconazole use is limited by its side effect profile and activity spectrum. Itraconazole appears to be better tolerated and less toxic to liver function, does not cause adrenal suppression and is more active against Aspergillus and Sporothrix schenckii. Fluconazole appears to be a highly promising agent due its highly favorable pharmacokinetic profile; it is water soluble, is well tolerated, is not metabolized to inactive constituents, it has a long half-life and, unlike the other azoles, high cerebrospinal fluid levels are readily attained for consideration in meningeal mycoses. It remains to be determined what place these new triazoles have in managing immunosuppressed patients including those with acquired immune deficiency syndrome known as AIDS. Other experimental antifungal agents, including ambruticin, amphotericin B methyl ester and saramycetin are also described. Sales figures are presented of drugs marketed in the United States for the systemic mycoses and reflect the growing problem of fungal diseases in the population.Presented as part of the Everett S. Beneke Symposium in Mycology, May 27, 1988.     

In vitro stimulation and inhibition of steroid hormone release from postovulatory follicles of the tilapia,Oreochromis mossambicus

Summary Postovulatory follicles of the tilapia, Oreochromis mossambicus, were incubated with graded doses of salmon gonadotropin to identify the steroid hormones released by this tissue. In addition, the effects of either cytochalasin B or colchicine on steroid hormone release were studied. After the incubation, the tissue was examined by electron microscopy. Postovulatory follicles released testosterone and estradiol-17B in a dose-dependent manner with gonadotropin. There was no detectable release of progesterone or 17a-OH-progesterone. When stimulated with high doses of gonadotropin, the steroidogenic cells showed an increase in smooth endoplasmic reticulum, Golgi complexes, and lipid droplets. Also, microfilaments became arranged in orderly bundles and were found close to the numerous secretory vesicles and lipid droplets. Upon incubation with gonadotropin and either colchicine or cytochalasin B, the cells still appeared steroidogenic, but the filaments were not organized nor associated with vesicles or lipid droplets. Release of steroid hormone decreased significantly. Also in these tissues, vesicles were no longer numerous in the apical region of the granulosa cells, but were located primarily near smooth endoplasmic reticulum and Golgi complexes. This suggests that disruption of the cytoskeleton results in reduced steroid hormone synthesis or release.     

γ-Aminobutyric Acid Function in the Rat Striatum Is Under the Double Influence of Nigrostriatal Dopaminergic and Thalamostriatal Inputs: Two Modes of Regulation?

Glutamic acid decarboxylase (GAD), gamma-[3H]-aminobutyric acid [( 3H]GABA) high-affinity uptake into synaptosomes, and endogenous GABA content were measured in the rat striatum 2-3 weeks following 6-hydroxydopamine injection in the ipsilateral substantia nigra to destroy the nigrostriatal dopaminergic pathway and after kainic acid injection into the centromedial-parafascicular complex of the ipsilateral thalamus to lesion the thalamostriatal input. Both lesions resulted in apparent GAD increase concomitant with a decreased [3H]GABA uptake into striatal synaptosomes. GABA content was increased selectively following the dopaminergic lesion. Kinetic analysis of the uptake process for [3H]GABA showed selectively a decreased Vmax following the dopaminergic lesion; in animals with thalamic lesion, however, the change only concerned the Km, which showed a decreased affinity of the transport sites for [3H]GABA. Determination of Km and Vmax for GAD action on its substrate glutamic acid showed an increased affinity of GAD for glutamic acid in the case of the dopaminergic lesion without any change in Vmax, whereas the thalamic lesion resulted in GAD increase concomitant with a selective increase in Vmax. These data suggest that striatal GABA neurons are under the influence of nigrostriatal dopaminergic neurons which may reduce the GABA turnover, whereas the exact nature of the powerful control also revealed on these neurons following thalamic lesion remains to be determined. Both lesions induced adaptive neurochemical responses of striatal GABA neurons, possibly reflecting in the case of the dopaminergic deprivation an increased GABA turnover.     

Antigenic mapping of a human λ light chain: Correlation with three dimensional structure

Although the amino acid sequence and three-dimensional structure of human immunoglobulin light chains have been known for more than 15 years, the location of antigenic markers characteristic of chains has not been determined. Here, we use a set of synthetic overlapping peptides to completely model the sequence of the chain Mcg and test these for the binding or rabbit and goat antisera specific for chain determinants. We assess peptide contributions to -antigenic reactivity and also to identify a portion of C-region where conformational factors contribute to the antigenicity. Specific determinants occur both in the constant and variable (first and third framework) domains of the molecule. The fourth framework of the variable region, a segment specified by the joining gene, is also recognized and cross-reacts antigenically with the homologous region of T cell receptor chains. Major specific determinants are localized in the N- and C-terminal segments, which are linear and devoid of major conformational folding. Other segments that are strongly antigenic, such as the third framework of the V region (residue 78–93) and a segment of the constant region (residues 177–192), show strong conformational dependence in antigenicity.     

Persistent measles virus infection enhances major histocompatibility complex class I expression and immunogenicity of murine neuroblastoma cells

The effect of persistent measles virus infection on the expression of major histocompatibility complex (MHC) class I antigens was studied. Mouse neuroblastoma cells C1300, clone NS20Y, were persistently infected with the Edmonston strain of measles virus. The persistently infected cell line, NS20Y/MS, expressed augmented levels of both H-2K^k and H-2D^d MHC class I glycoproteins. Activation of two interferon(IFN)-induced enzymes, known to be part of the IFN system: (2–5)oligoadenylate synthetase and double-stranded-RNA-activated protein kinase, was detected. Measles-virus-infected cells elicited cytotoxic T lymphocytes that recognized and lysed virus-infected and uninfected neuroblastoma cells in an H-2-restricted fashion. Furthermore, immunization of mice with persistently infected cells conferred resistance to tumor growth after challenge with the highly malignant NS20Y cells. The rationale for using measles virus for immunotherapy is that most patients develop lifelong immunity after recovery or vaccination from this infection. Patients developing cancer are likely to have memory cells. A secondary response induced by measles-virus-infected cells may therefore induce an efficient immune response against non-infected tumour cells.     

Effects of feeding enrichment on behavior of three species of captive bears

Bears are extremely popular among the zoo-going public, yet while many zoo exhibits have undergone dramatic design changes in recent years, most bears continue to be housed in moated grottos constructed largely of gunite. In these traditional exhibits they frequently demonstrate stereotypic locomotor patterns and are often encouraged by the public to beg. Thus, the manner in which most captive bears are exhibited does not facilitate conservation education. It is possible, however, to provide bears with opportunities to demonstrate species-typical feeding and foraging behaviors, even in standard exhibits. Subjects were four individuals of three bear species. Feeding enrichment was provided to one bear per week during three mornings during the summers of 1989 and 1990. Overall, animals were more active, less passive and less often engaged in abnormal behaviors during sessions with enrichment. Effects showed individual variation and were more profound during the second year of the study, when a greater variety of enrichment items was presented. These results suggest that simple and inexpensive methods of enrichment may have a significant, positive influence on the behavior of captive bears. © 1992 Wiley-Liss, Inc.     

Murine erythrocyte ankyrin cDNA: highly conserved regions of the regulatory domain

Ankyrin is an essential link between cytoskeletal proteins, such as spectrin, and membrane bound proteins, such as protein 3, the erythrocyte anion exchanger. Although the amino acid structure of human ankyrin is known, the functional regions have been only partially defined. Sequence comparisons between mouse and human ankyrin offer one mechanism of identifying highly conserved regions that probably have functional significance. We report the isolation and sequencing of a series of overlapping murine erythroid ankyrin (Ank-1) cDNAs from spleen and reticulocyte libraries (total span 6238 bp) and identify potentially important regions of murine-human reticulocyte ankyrin homology. Comparison of the predicted peptide sequences of mouse and human erythroid ankyrins shows that these ankyrins are highly conserved in both the N-terminal, protein 3 binding domain (96% amino acid identity) and in the central spectrin-binding domain (97% identity), but differ in the C-terminal regulatory domain (79% identity). However, the C-terminal regulatory domain contains two regions of peptide sequence that are perfectly conserved. We postulate these regions are important in the regulatory functions of this domain.     

Desorption chemical ionization mass spectrometry of 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholines and analogues

Ammonia desorption chemical ionization of ether-linked phospholipids of the type 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine (platelet-activating factors) and a series of analogues revealed a systematic fragmentation pattern that is characteristic for these compounds. The predominant ions included the protonated molecular ion and a series of fragments derived from the molecular ion having the following nominal mass losses: MH-14, MH-42, MH-59, and MH-183. Deuterated ammonia was used to elucidate the nature of several fragments. In addition, desorption chemical ionization was used to quantitate 1-O-hexadecyl-2-O-acetyl-sn-glycero-3-phosphocholine at the nanogram/sample level.