Ultrastructure of type-I salivary-gland acini in four species of ticks and the influence of hydration states on the type-I acini ofAmblyomma americanum

We describe the ultrastructure of type-I salivary-gland acini in two argasid and two ixodid species. The basic cell types in the agranular or type-I acini, and their associations, are very similar in argasids and ixodids; therefore, we propose an anatomical nomenclature for cells in the type-I acinus based on the adult ixodidsAmblyomma americanum andDermacentor variabilis, and the argasid adultArgas (Persicargas) arboreus and on nymphalOrnithodoros moubata. Four cell types were present in all specimens: one central lamellate cell, a variable number of peripheral lamellate cells, a variable number of peritubular cells depending on the species, and one circumlumenal cell. The lamellate cells had infolded basal plasma membranes that presented an amplified surface area to the hemolymph. These cells most likely secreted the fluid involved in water vapor uptake by ticks. ForAmblyomma americanum females, abundant K⁺-dependent, ouabain-sensitive Na⁺, K⁺-ATPase complexes were located on the infolded basal plasma membranes of the lamellate cells. Apical membranes of the lamellate cells, and plasma membranes of other cell types in the acinus had little or no evidence of Na⁺, K⁺-ATPase activity. Only the central lamellate cell extended from the hemolymph of the acinus to its lumen; peripheral cells did not contact the lumen. Except when the ticks were rehydrating, lipid inclusions were common features in the lamellate cells of the ixodids. Lipid inclusions were not seen in argasid type I acini; however, glycogen deposits were common. To determine if acinar cells respond to the changing hydration state of the tick, unfed femaleA. americanum were subjected to dehydration/rehydrating conditions. During rehydration, mitochondria in the lamellate cells changed from a matrix of medium electron-density and intermembrane space (orthodox configuration) to a matrix of greater density and larger intermembrane space (condensed configuration). The orthodox configuration was consistently observed in control and dehydrating ticks. The condensed configuration was the norm for mitochondria in lamellate cells of rehydrating ticks. Lipid inclusions were depleted in the rehydrating ticks compared to control or dehydrating ticks. Acini appeared to be reverting to the control or desiccated state when ticks were returned to low humidity, suggesting that these changes were cyclical. Nymphs ofO. moubata subjected to the same dehydration/rehydrating conditions showed no obvious ultrastructural changes.     

Stimulated T cell and natural killer (NK) cell lines fail to synthesize leukotriene B4

The ability of leukotriene B4 (LTB4) to influence T cell and natural killer (NK) cell functions makes the question of LTB4 generation by these cells important to address. Consequently, LTB4 generation was evaluated in a human (Jurkat), and in a murine (EL-4) T cell line as well as in a rat NK cell line (RNK-16). Incubation of each of the 3 cell lines with [1-14C]arachidonic acid alone or in the presence of phytohemagglutinin (PHA), of calcium ionophore A23187, or of concanavalin A (Con A) plus the phorbol ester 12-0-tetradecanoylphorbol-13-acetate (TPA) failed to generate radiolabelled LTB4 or other eicosanoids as determined by thin layer radiochromatography. Using two different radioimmunoassays for LTB4 also failed to demonstrate the generation of LTB4 under basal or stimulated conditions. These results support earlier studies that demonstrate that T cells are not capable of de novo synthesis of prostaglandins, thromboxanes, or leukotrienes and also provide evidence that NK cells also do not have the capacity to generate LTB4 or other eicosanoids. Our findings are also critically discussed in relation to studies claiming eicosanoid synthesis by T cells.     

Glutamate is the endogenous amino acid selectively released by rat hippocampal mossy fiber synaptosomes concomitantly with prodynorphin-derived peptides

The release of endogenous amino acids from depolarized rat hippocampal mossy fiber synaptosomes was investigated to assess the possible role(s) of glutamate and aspartate in mediating the excitatory mossy fiber synaptic input. The relative proportions of prodynorphin-derived peptides concomitantly released with amino acids were also determined to further characterize the biochemical basis for mossy fiber synaptic transmission. Of the 18 amino acids shown to be present in superfusate fractions by liquid chromatographic analysis, only glutamate was released at a significantly enhanced rate from K⁺-stimulated (35 mM KCl) mossy fiber nerve endings. The rates of glutamate and aspartate release were increased by 360±27% and 54±12% over baseline respectively. However, the K⁺-evoked release of glutamate was substantially more Ca²⁺-dependent (80%) than was the release of aspartate (49%). The veratridine (45 M)-evoked release of both acidic amino acids was entirely blocked by 1 M tetrodotoxin. Depolarization (45 mM KCl) also stimulated the release of the four prodynorphin (Dyn) products examined, in a rank order of Dyn B >> Dyn A(1–17) > Dyn A(1–8) >> Dyn A(1–13), with Dyn B efflux increasing by more than 5-fold over baseline values. These results suggest that the predominant excitatory amino acid in hippocampal mossy fiber synaptic transmission may be glutamate and that this synaptic input may be modulated by at least four different products of prodynorphin processing.The animals involved in this study were procured, maintained and used in accordance with the Animal Welfare Act and the Guide for the Care and Use of Laboratory Animals prepared by the Institute of Laboratory Animal Resources—National Research Council.     

One-step gene disruption by cotransformation to isolate double auxotrophs in Candida albicans

Summary The Candida albicans LEU2 gene was disrupted by substituting lambda DNA for a small deletion within the LEU2 gene. Cotransformation with a selectable URA3 ARS vector was used to introduce a linear fragment containing the disruption into the genome of a C. albicans ura3 deletion mutant. Cotransformants containing the lambda DNA were identified by colony hybridization and the URA3 plasmid was subsequently cured. Leu2 disrupted heterozygotes were detected by Southern hybridization and one disruptant was subsequently treated with UV irradiation. Only one leu2 ura3 mutant (SGY-484) was isolated out of 11,000 mutagenized cells. SGY-484 was transformed to Leu⁺ with either the C. albicans or Saccharomyces cerevisiae LEU2 gene. Southern hybridization analysis revealed that the mutant is not homozygous for the disruption; the leu2 mutation reverts and is most likely a point mutation. Unexpectedly, an ade2 ura3 mutant was isolated from the same mutagenesis.     

Vacuolar H(+)-translocating pyrophosphatases: a new category of ion translocase.

The membrane surrounding the central vacuole of plant cells contains an H(+)-translocating ATPase (H(+)-ATPase) and an H(+)-translocating inorganic pyrophosphatase (H(+)-PPase). Both enzymes are abundant and ubiquitous in plants but the H(+)-PPase is unusual in its exclusive use of inorganic pyrophosphate (PPi) as an energy source. The lack of sequence identity between the vacuolar H(+)-PPase and any other characterized ion pump implies a different evolutionary origin for this translocase. The existence of the vacuolar H(+)-PPase, in conjunction with increasing recognition of PPi as a key metabolite in plant systems, necessitates reconsideration of ATP as the primary energy source for membrane transport in plant cells.     

Suppressor T lymphocytes from lepromatous leprosy skin lesions

The immune response in leprosy forms a spectrum with lepromatous leprosy patients exhibiting specific unresponsiveness to antigens of Mycobacterium leprae. This unresponsiveness is thought to be related to the prevalence of T8-positive lymphocyte in these lepromatous lesions. To analyze the immunoregulatory function of these T8 cells, we developed simple procedures to extract lymphocytes from skin biopsy specimens of patients with leprosy. These lymphocytes were sorted for T8 and T4 positive cells, and cell lines were established by expansion with interleukin 2 (IL 2) and irradiated feeder cells. All T8 positive lines tested were positive for IL 2 receptors and HLA-DR determinants. These lines were additionally assayed for lepromin-induced suppression of the normal peripheral blood lymphocyte Con A proliferative response. Thirteen of 32 lines from six lepromatous patients showed significant suppressor activity, whereas nine lines from six tuberculoid patients and one line from normal peripheral blood failed to show suppression (p less than 0.001). Taken together, the finding of M. leprae-triggered suppressor cells within lepromatous skin lesions may in part explain the M. leprae unresponsiveness of lepromatous leprosy patients.     

MATCH-UP/MATRIX: a microcomputer program designed to search for protein primary structure homology

MATCH-UP/MATRIX is a program designed to aid the investigatorinterested in determining primary protein structure. It is writtenin Applesoft BASIC for the Apple lle microcomputer. MATCH-UPwill survey any set of proteinaceous materials for amino acidsequence homology; however, it is primarily intended to comparethe structures of newly sequenced peptides with the establishedstructure of a protein with suspected homology. Any peptide-to-proteinalignment which shows a homology greater than or equal to thepercentage specified by the user will result in output. MATRIXwill compare the sequences of two proteins (peptides) in whateveralignment specified by the user and is intended to spot insertionsand/or deletions between structures. Received on December 2, 1985; accepted on March 10, 1986     

Asthma mortality: comparison between New Zealand and England.

Causes for the high mortality from asthma in New Zealand were investigated by comparing deaths from asthma in caucasian subjects aged 15-64 in New Zealand with those from asthma in the same age group in two regions in England. There were no significant differences in the accuracy of death certification. The verified asthma mortality in New Zealand (4.2/100,000) was over twice that in England. Many characteristics of patients and management, including poor compliance with treatment and deficiencies in long term and emergency care, were qualitatively similar in the two countries. New Zealand had an apparently higher rate of non-preventable deaths from asthma, suggesting a greater severity of asthma in New Zealand. In both countries, however, most deaths were associated with poor assessment, underestimation of severity and inappropriate treatment (over-reliance on bronchodilators and underuse of systemic corticosteroids), and delays in obtaining help. A greater frequency of some of these deficiencies in management remains a possible additional explanation for part of the excess mortality in New Zealand.