SEC7 encodes an unusual, high molecular weight protein required for membrane traffic from the yeast Golgi apparatus

Saccharomyces cerevisiae with mutations at the sec7 locus are pleiotropically deficient in protein transport within the Golgi apparatus and proliferate a large array of Golgi cisternae at a restrictive growth temperature (37 degrees C). The SEC7 gene and its product (Sec7p) have been evaluated by molecular cloning and sequence analysis. Two genes that allow sec7 mutant cells to grow at 37 degrees C are represented in wild-type yeast DNA libraries. A single copy of the authentic SEC7 gene permits growth of mutant cells, whereas the other gene suppresses growth deficiency only when expressed from a multicopy plasmid. The SEC7 gene is contained on a 8.4-kilobase pair SphI restriction fragment, portions of which hybridize to a single 6-kilobase pair mRNA. The gene is essential for yeast vegetative growth. DNA sequence analysis of this region detects a single open reading frame with the potential to encode a 2008-amino acid-long hydrophilic protein of 230 kDa. Putative Sec7p contains an unusual, highly charged acidic domain of 125 amino acids with 29% glutamate, 18% aspartate, and 21% serine. Within this region, stretches of 14 consecutive glutamate residues and 13 consecutive glutamates/aspartates are predicted. This domain in Sec7p may serve a structural role to interact with lipids or proteins on the cytoplasmic surface of the Golgi apparatus.

An audit of electroconvulsive therapy

OBJECTIVE

To audit five years experience with electroconvulsive therapy (ECT).

METHOD

Retrospectively audit the case records of all patients receiving ECT from 1981 to 1985. This enabled us to compare our clinical practise with published guidelines for optimal use of ECT.

RESULTS

Review 486 courses of ECT yielded a total of 3936 treatments. The audit identified several areas of clinical practise which do not comply with recommended standards for ECT.

GAL2 codes for a membrane-bound subunit of the galactose permease in Saccharomyces cerevisiae

The gene encoding the galactose permease of Saccharomyces cerevisiae (GAL2) was cloned. The clone restores galactose permease activity to gal2 yeasts and is regulated by galactose in a manner similar to other GAL gene products (GAL1, -7, and -10). Experiments with temperature-conditional secretory mutants indicated that transport of the GAL2 gene product to the cell surface requires a functional secretory pathway. In addition, gene fusions were constructed between the GAL2 gene and the Escherichia coli lacZ gene. The GAL2-lacZ gene fusions code for galactose-regulated beta-galactosidase activity in yeasts. The beta-galactosidase activity was found to be membrane bound.

Chlorpromazine effects on stereotypic and conditioned behaviour of severely retarded patients--a pilot study

An attempt was made to test the hypothesis that anti-psychotic medication may induce adaptive changes by suppressing stereotypic behaviour. Six profoundly retarded residents were selected for the presence or absence of stereotypic behaviour and tested in a placebo controlled, cross-over study. Chlorpromazine caused noticable drowsiness in all subjects over the 2-week drug period. Body rocking was significantly suppressed in the wards, but other clinical behaviours were not influenced by the drug. Performance on an operant conditioning task was significantly impaired in most subjects. Body rocking, which was also assessed during operant responding, was unrelated to presence or absence of clinical stereotypy, observed on the wards. The results were discussed in terms of chlorpromazine's clinical effects and improved ways of assessing the hypothesis that anti-psychotic drugs may enhance adaptive behaviour in some retarded individuals.

Yeast secretory mutants that block the formation of active cell surface enzymes

Yeast cells secrete a variety of glycosylated proteins. At least two of these proteins, invertase and acid phosphatase, fail to be secreted in a new class of mutants that are temperature-sensitive for growth. Unlike the yeast secretory mutants previously described (class A sec mutants; Novick, P., C. Field, and R. Schekman, 1980, Cell., 21:205-420), class B sec mutants (sec 53, sec 59) fail to produce active secretory enzymes at the restrictive temperature (37 degrees C). sec 53 and sec 59 appear to be defective in reactions associated with the endoplasmic reticulum. Although protein synthesis continues at a nearly normal rate for 2 h at 37 degrees C, incorporation of [3H]mannose into glycoprotein is reduced. Immunoreactive polypeptide forms of invertase accumulate within the cell which have mobilities on SDS PAGE consistent with incomplete glycosylation: sec 53 produces little or no glycosylated invertase, and sec 59 accumulates forms containing 0-3 of the 9-10 N-linked oligosaccharide chains that are normally added to the protein. In addition to secreted enzymes, maturation of the vacuolar glycoprotein carboxypeptidase Y, incorporation of the plasma membrane sulfate permease activity, and secretion of the major cell wall proteins are blocked at 37 degrees C.

Compromises between water-use efficiency and nitrogen-use efficiency in five species of California evergreens

In five California evergreen trees and shrubs cooccurring in this study but most common in habitats of different moisture availability, leaf nitrogen was a major determinant of photosynthetic capacity. Within each species, stomatal conductance was highly correlated with photosynthetic capacity, resulting in little variation in the concentration of CO₂ in the intercellular spaces. Among species, intercellular CO₂ concentrations varied significantly. Under controlled conditions, the leaves that realized the highest photosynthesis per unit of leaf nitrogen tended to realize the lowest photosynthesis per unit of water transpired. The ratio of photosynthesis to transpiration, an instantaneous measure of intrinsic water-use efficiency, was highest in the species commonly found in the direst habitats and lowest in the species most common in the wettes habitats.

Photocontrol of the Functional Coupling between Photosynthesis and Stomatal Conductance in the Intact Leaf : Blue Light and Par-Dependent Photosystems in Guard Cells

The photocontrol of the functional coupling between photosynthesis and stomatal conductance in the leaf was investigated in gas exchange experiments using monochromatic light provided by lasers. Net photosynthesis and stomatal conductance were measured in attached leaves of Malva parviflora L. as a function of photon irradiance at 457.9 and 640.0 nanometers.Photosynthetic rates and quantum yields of photosynthesis were higher under red light than under blue, on an absorbed or incident basis.Stomatal conductance was higher under blue than under red light at all intensities. Based on a calculated apparent photon efficiency of conductance, blue and red light had similar effects on conductance at intensities higher than 0.02 millimoles per square meter per second, but blue light was several-fold more efficient at very low photon irradiances. Red light had no effect on conductance at photon irradiances below 0.02 millimoles per square meter per second. These observations support the hypothesis that stomatal conductance is modulated by two photosystems: a blue light-dependent one, driving stomatal opening at low light intensities and a photosynthetically active radiation (PAR)-dependent one operating at higher irradiances.When low intensity blue light was used to illuminate a leaf already irradiated with high intensity, 640 nanometers light, the leaf exhibited substantial increases in stomatal conductance. Net photosynthesis changed only slightly. Additional far-red light increased net photosynthesis without affecting stomatal conductance. These observations indicate that under conditions where the PAR-dependent system is driven by high intensity red light, the blue light-dependent system has an additive effect on stomatal conductance.The wavelength dependence of photosynthesis and stomatal conductance demonstrates that these processes are not obligatorily coupled and can be controlled by light, independent of prevailing levels of intercellular CO(2). The blue light-dependent system in the guard cells may function as a specific light sensor while the PAR-dependent system supplies a CO(2)-modulated energy source providing functional coupling between the guard cells and the photosynthesizing mesophyll.

Photosynthetic capacity in relation to leaf position in desert versus old-field annuals

Desert annuals of Death Valley, California have higher average light-saturated photosynthetic capacities and leaf nitrogen contents than do early-successional annuals of Illinois. The leaves of annuals in the light-unlimited Death Valley environment change little in specific weight, nitrogen, or photosynthetic capacity with age. In contrast, these properties decrease markedly with age in the leaves of the Illinois annuals even in leaves not exposed to the usual shading that accompanies canopy development. These results are interpreted in a carbon-gained-per-nitrogen-invested context.

Identification of 23 complementation groups required for post-translational events in the yeast secretory pathway

Cells of a Saccharomyces cerevisiae mutant that is temperature-sensitive for secretion and cell surface growth become dense during incubation at the non-permissive temperature (37 degrees C). This property allows the selection of additional secretory mutants by sedimentation of mutagenized cells on a Ludox density gradient. Colonies derived from dense cells are screened for conditional growth and secretion of invertase and acid phosphatase. The sec mutant strains that accumulate an abnormally large intracellular pool of invertase at 37 degrees C (188 mutant clones) fall into 23 complementation groups, and the distribution of mutant alleles suggests that more complementation groups could be found. Bud emergence and incorporation of a plasma membrane sulfate permease activity stop quickly after a shift to 37 degrees C. Many of the mutants are thermoreversible; upon return to the permissive temperature (25 degrees C) the accumulated invertase is secreted. Electron microscopy of sec mutant cells reveals, with one exception, the temperature-dependent accumulation of membrane-enclosed secretory organelles. We suggest that these structures represent intermediates in a pathway in which secretion and plasma membrane assembly are colinear.

Localized secretion of acid phosphatase reflects the pattern of cell surface growth in Saccharomyces cerevisiae

Secretion of cell wall-bound acid phosphatase by Saccharomyces cerevisiae occurs along a restricted portion of the cell surface. Acid phosphatase activity produced during derepressed synthesis on a phosphate-limited growth medium is detected with an enzyme-specific stain and is localized initially to the bud portion of a dividing cell. After two to three generations of phosphate-limited growth, most of the cells can be stained; if further phosphatase synthesis is repressed by growth in excess phosphate, dividing cells are produced in which the parent but not the bud can be stained. Budding growth is interrupted in alpha-mating-type cells by a pheromone (alpha-factor) secreted by the opposite mating type; cell surface growth continues in the presence of alpha-factor and produces a characteristic cell tip. When acid phosphatase synthesis is initiated during alpha-factor treatment, only the cell tip can br stained; when phosphate synthesis is repressed during alpha-factor treatment, the cell body but not the tip can be stained. A mixture of derepressed alpha cells and phosphatase-negative alpha cells form zygotes in which mainly one parent cell surface can be stained. The cell cycle mutant, cdc 24 (Hartwell, L.H. 1971. Exp. Cell Res. 69:265-276), fails to bud and, instead, expands symmetrically as a sphere at a nonpermissive temperature (37 degrees C). This mutant does not form a cell tip during alpha-factor treatment at 37 degrees C, and although acid phosphatade secretion occurs at this temperature, it is not localized. These results suggest that secretion reflects a polar mode of yeast cell- surface growth, and that this organization requires the cdc 24 gene product.

Multiple-drug chemotherapy in the management of acute lymphocytic leukemia during pregnancy

Acute leukemia associates with pregnancy is relatively uncommon, and because of the age distribution of patients with acute leukemia the majority have had acute granulocytic leukemia. Various combinations of chemotherapeutic agents are commonly employed now to obtain maximal benefit, related to differing pharmacologic activities of single agents. The present case documents the use of multiple cytotoxic drugs in the management of acute lymphocytic leukemia, with successful delivery of a normal infant. In this patient severe anemia and potentially teratogenic drugs did not appear to affect the fetus.

Survival of anaerobic and aerobic bacteria on cotton swabs in three transport systems

The capacity of aerobic and anaerobic bacteria to survive on cotton swabs placed into a dry gassed-out CO2-filled tube (DGT), dry sterile aerobic tube (DAT), and a tube containing a modified Stuarts' transport medium (MST), was assessed. Pseudomonas aeruginosa increased in numbers by 2 and 3 logs when stored in MST and DAT, respectively. The viability of P. aeruginosa, although retarded when compared to MSA and DAT, was not adversely affected by the CO2 environment in the DGT. The MST maintained relatively constant numbers of Streptococcus pyogenes during the 48-h storage period. The DAT and the DGT were unable to maintain the viability of S. pyogenes. Staphylococcus aureus, when stored in a DGT, DAT, or MST, was maintained in relatively constant numbers throughout the entire storage period. Of the four anaerobic bacteria evaluated (Bacteroides fragilis ssp. thetaiotaomicron, Bacteroides melaninogenicus ssp. asaccharolyticus, Fusobacterium nucleatum, and Peptostreptococcus anaerobius), only B. fragilis ssp. thetaiotamicron survived the 48-h storage period in the DGT. Under these test conditions the DGT did not adequately maintain the viability of the majority of anaerobic bacteria tested (when held on cotton swabs). However, the MST did maintain the viability of all species tested for at least the first 2 h of storage.

The Immune Response of Mice to Serratia Marcescens LPS or Intact Bacteria

Injection of adult mice with lipopolysaccharide (LPS) somatic antigen, or a heat-killed vaccine of Serratia marcescens resulted in rapid appearance of specific antibody-forming cells in the spleen, as well as other lymphoid tissues such as the mesenteric nodes and the thymus. Either immunogen in a dose of 50 µg resulted in a maximum cellular antibody response 3 to 5 days later; higher or lower doses resulted in a lesser response. Injection of 500 or 750 µg antigen gave the least response. In mice injected with the high doses of antigen, there was no compensatory increase in the number of antibody-forming cells in lymphoid organs other than the spleen. Regardless of antigen dose used or the time period after immunization antiglobulin facilitation yielded no evidence for additional plaque-forming cells. All concentrations of antigen gave a rapid increase in hemagglutinin and bacterial agglutinin titers, the vaccine giving the highest titers. Mice injected with 500 or 750 µg of either form of antigen had lower serum titers. Mice given the higher doses of either LPS or vaccine displayed a marked increase in the number of nonspecific antibody-forming cells to sheep erythrocytes. These results are viewed as evidence for development of immunologic tolerance to large doses of Serratia antigens, either vaccine or LPS. The toxicity of the antigenic preparations did not appear to be involved in the immunodepression. Both the antigenic state and dose markedly influenced the number of antibody-forming cells appearing after immunization.