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.     

Effects of CaSO4 and NaCl on growth and nitrogen fixation ofLeucaena leucocephala

Effects and interactions of varying CaSO₄ and NaCl levels on growth and nitrogen fixation ofLeucaena leucocephala K8 were examined. Leucaena was grown in nutrient solution at four levels of CaSO₄ (0.5, 1.0, 2.5 and 5.0 mM) and NaCl (1, 25, 50 and 100 mM) in randomized blocks with five replications. While NaCl significantly reduced plant growth, additions of CaSO₄ increased plant height, leaf number, and biomass of salt treated plants. For the nonsaline treatments, high CaSO₄ levels slightly depressed growth, which contradicts suggestions that Leucaena has a high calcium requirement. A significant calcium/sodium interaction was not seen for nodule number or weight. Nodule number was significantly depressed by 100 mM NaCl and nodule weight of the salt stressed plants significantly increased as CaSO₄ concentration increased from 0.5 to 2.5 mM. Effects of NaCl and CaSO₄ on nitrogen content of plant parts were inconclusive. The promotion of Leucaena salinity tolerance by addition of CaSO₄ may be attributed to the effect of calcium in maintaing the selective permeability of membranes.     

Control ofThrips tabaci [Thysanoptera: Thripidae] on glasshouse cucumber using large introductions of predatory mitesAmblyseius barkeri [Acarina: Phytoseiidae]

The phytoseiid miteAmblyseius barkeri (Hughes) (=Amblyseius mckenziei Sch. & Pr.) was used for biological control ofThrips tabaci Lind. in 7 commercial glasshouses with cucumber (a total of 5780 m²). Predatory mites were introduced 3–4 times in densities ranging from 40 to 300/m² at each release. In 6 of the 7 glasshouses, control of thrips was satisfactory throughout the growing season. Thrips densities were kept below 15 individuals per leaf. In 1 glasshouse, thrips damage was seen on the fruits at densities of 25 thrips per leaf, but the thrips population was quickly reduced and remained at low densities for the next 3 months.      

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.     

Increased working capacity with hyperoxia in humans

The purpose of the study was to examine the influence of oxygen-breathing on maximal oxygen uptake (VO2max) and submaximal endurance performance. Six young women and five men rode a cycle-ergometer while breathing compressed air (normoxia, NOX) or a 55% O2 in N2 mixture (hyperoxia, HOX). The VO2max increased significantly by 12% (P less than 0.01) with HOX in the women but not in the men (+4%; nonsignificant). Maximal heart rate was also increased with HOX in the women but not in the men. Endurance time during work to exhaustion at 80% of normoxic VO2max was 41% longer in HOX than in NOX (P less than 0.025) with no significant difference between the men and the women. The variation among individuals was large. The oxygen uptake and respiratory quotient were not different in the two endurance tests, but pulmonary ventilation (VE) and blood lactate concentration were lower in HOX than in NOX, especially during the latter part of the task. Plasma base deficit (BDpl) increased initially by 3.5 mmol.l-1 during HOX and then stabilized. In NOX, a continuous increase was seen and the change was more than twice as large. Relative to BDpl, VE was higher in HOX than in NOX indicating a more efficient ventilatory compensation of the metabolic acidosis. The reduced ventilatory demand and lower metabolic acidosis in HOX in combination with lower relative exercise intensity may have contributed to the longer time to exhaustion. However, the pattern of individual variation suggested that other mechanisms were also involved.     

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.     

Mineralization budgets in sediment microcosms: Effect of the infauna and anoxic conditions

Abstract A number of sediment incubations were set up to reproduce some of the conditions used by Kristensen and Blackburn [1] and to make a comparison with their results. There were three types of microcosm: aerobic (OX), anaerobic (AN) and aerobic with Nephtys (NOX). In addition to other measurements, dissolved organic nitrogen (DON) pools and fluxes, were measured. The sediment in this experiment contained more particulate organic matter (POM). Nephtys (NOX) had the same effect as Nereis in increasing the rate of mineralization of POC and PON, compared with the OX-cores (2.1 and 2.6 times, respectively). Again, the AN-cores had a higher mineralization rate (loss of POM) than that of the OX-cores, but in addition, mineralization in NOX-cores was not significantly different from AN-cores. It was thus confirmed that anoxic mineralization could be as high, or higher, than the oxic process. Both the temporal patterns of O₂-and and CO₂-fluxes and their magnitudes were very similar to those reported earlier. This contrasts with the higher loss of POM in the present experiment. However, the loss of C in DOC (associated with the measured DON) can account for the extra POM loss. The pore-water profiles of σCO₂ and NH₄⁺ were similar to those in the earlier report, and the fluxes of σCO₂, O₂, NH₄⁺ and NO₃⁻ followed the same temporal pattern.     

Initial reactions in the mineralization of 2-sulfobenzoate by Pseudomonas sp. RW611

Abstract Pseudomonas sp. strain RW611 utilized the ammonium salt of 2-sulfobenzoate as sole source of carbon, sulfur, nitrogen, and energy. The xenobiotic sulfo substituent was dioxygenolytically eliminated as sulfite, which was then slowly oxidized to sulfate. 2,3-Dihydroxybenzoate, which resulted from desulfonation underwent meta -cleavage, mediated by 2,3-dihydroxybenzoate 3,4-dioxygenase activity. This enzyme was inhibited by 3-chlorocatechol and 2,3,4-trihydroxybenzoate.     

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.