POPULATION STRUCTURE IN ZAMIA DEBILIS (ZAMIACEAE) I. SIZE CLASSES,LEAF PHENOLOGY,AND LEAF TURNOVER

Population structure, leaf phenology and leaf turnover were followed over a 29-month period in Zamia debilis L.f. ex Aiton (Zamiaceae), an understory species in the Cambalache Forest in northern Puerto Rico. It was not possible to determine plant age or to measure the subterranean stems; size classes based on leaf number and leaf × leaflet number indices were used to determine population structure. Despite seasonal and year to year fluctuations in leaf number at the individual and population level, population profiles remained relatively constant. At any one time, over 50% of the population was composed of unbranched individuals with one or two leaves. Only 7% of the plants were branched. Plants with seven or more leaves comprised at a maximum 8% of the population, but accounted for 28% of the total foliage. Size classes based on leaf number and on a leaf × leaflet index gave approximately reverse J-shaped curves typical of trees with shade tolerant seedlings and saplings. New leaves emerged throughout the year, with a peak at the beginning of the rainy season in May or June and lowest production during the dry months of February through April. Average leaf life expectancy was approximately 2.3 years. Leaf death occurred over an extended period of time by the loss of individual leaflets. Patterns in leaf production and loss differed between few- and many-leaved plants. On the average, as the number of mature leaves on a plant increased, time between emergence of new leaves decreased. In many-leaved plants more than one event of new leaf emergence per year was common. Individuals with one to three mature leaves and individuals with four or more mature leaves differed in their response to water stress: few-leaved plants generally reduced the rate of new leaf production and retained old leaves longer. Plants with more than three leaves continued to produce new leaves, but the rate of leaf mortality increased so that most had a net leaf loss. There was no evidence that leaf emergence or retention were affected by cone production or seed maturation.     

Fluidized bed design parameters affecting novel lactic Acid downstream processing.

Lactic acid purification was directly done from fermentation utilizing a fluidized bed column refilled with a strong anionic exchange resin. The purpose of this work was to study the influence of two important design parameters, bed-diameter (D) and bed-height (H), in the lactic acid binding and elution capacity of the matrix. By changing the settled bed height from 2.5 to 5 cm for each diameter of column analyzed it was possible to obtain an 50% increase in the binding capacity of the resin in all experiments. This fact was attributed to a higher contact time between the culture broth and the anionic resin produced by the increase of back mixing and lactic acid residence time.     

Development of a fermentation procedure to produce a tempe-related food using common beans as substrate

Summary A basic procedure was developed to produce a tempe-like product using the mouldRhizopus oligosporus and black common beans (Phaseolus vulgaris) as substrate. The initial pH of the substrate was 5.8, and fermentation was conducted at 37°C with a relative humidity of 70% for 72 hrs. Levels of soluble solids and soluble protein increased dramatically as a result of fermentation. Some changes were as well observed in fatty acid contents of fermented samples. It was concluded that the common bean used was an acceptable substrate for preparing this product.     

Studies on the simultaneous production of single cell protein and polygalacturonase fromKluyveromyces fragilis

Summary Kluyveromyces fragilis produces polygalacturonase (PG) on a lactose medium. Although the enzyme is normally repressed at high aeration levels, significant amounts of PG can be produced under such conditions when pectin is added as inducer. The productivity and yield of cell mass were not significantly affected by the presence of inducer, suggesting potential applications to current single cell protein processes from whey.     

Effect of temperature and long-term operation on passively immobilizedZymomonas mobilis for continuous ethanol production

Summary A fibrous support was used forZ. mobilis immobilization. The system showed a broad optimum temperature range (25–35°C) for highest ethanol productivity, ethanol yield and glucose conversion during continuous fermentation of a 100 g/L glucose medium. Ethanol production and glucose conversion kept steady during two months of continuous operation at D=1h^–1.     

Ca2+- and voltage-dependent K+ conductance in dispersed parathyroid cells

The membrane ionic conductances of dispersed parathyroid cells kept in primary culture were studied using the "whole-cell" and "inside-out excised patch" variants of the patch-clamp technique. The major component of the total current was a voltage-dependent outward K+ current without an appreciable inward current. The amplitude of the K+ current was markedly reduced when free internal Ca2+ was buffered by addition of 10 mM EGTA. Recordings of single-channel current in excised membrane patches revealed the presence of K+ channels with large unitary conductance (200 pS in symmetrical 130 mM K+ solutions) which were also activated by depolarization when internal Ca2+ concentration was about 10(-5)-10(-6) M. At any membrane voltage these channels were closed most of the time at internal Ca2+ concentrations lower than 10(-10) M. These results demonstrate the existence of a Ca2+- and voltage-dependent K+ permeability in parathyroid cells which may participate in the unusual membrane potential changes induced by alterations of external Ca2+ and, possibly, in the regulation of parathormone secretion.     

Deletion analysis of sucrose metabolic genes from a Salmonella plasmid cloned in Escherichia coli K12

The sucrose operon from pUR400, a 78-kbp conjugative Salmonella plasmid, was cloned in Escherichia coli K12. The operon was located in a 5.7-kbp SalI restriction fragment and was subcloned, in each of two possible orientations, using the expression vector pUC18. The insert DNA was restriction mapped and duplicate restriction sites in the insert and in the polylinker of the vector were used to create various deletions promoter distal in the operon sequence. Additional deletions were made with the restriction exonuclease Bal31. Cells containing hybrid plasmids with specified deletions lacked the ability to transport sucrose or were constitutive for hydrolase and/or uptake activities. The scrA (enzyme IIScr) and scrR (regulatory) genes resided within 2900-bp SmaI-SalI DNA fragment and were assigned the order scrB, scrA, scrR. An amplified sucrose-inducible gene product, Mr 68,000, was detected only in the membrane fraction from recombinant cells that contained plasmid with the intact operon sequence. This protein represented 11% of the total membrane protein and was resistant to extraction with 0.5 M sodium chloride, 2% Triton X-100, and 0.5% sodium deoxycholate. The protein did not appear to be the product of either the scrA, scrB, or scrR gene and may therefore represent a previously unidentified membrane-bound sucrose protein. A new gene, scrC, is proposed. In addition, the cloned 5.7-kbp SalI and 2.5-kbp SmaI-SalI DNA fragments failed to hybridize to chromosomal DNA from Bacillus subtilis, Streptococcus lactis, Streptococcus mutans, and Lactobacillus acidophilus as well as to DNA from a sucrose plasmid from Salmonella tennessee. However, the probes showed weak homology with a 20-kbp EcoRI restriction fragment from Klebsiella pneumoniae.     

Covalent labeling of opioid receptors with 3H-D-Ala2-Leu5-enkephalin chloromethyl ketone. I. Binding characteristics in rat brain membranes

The chloromethyl ketone derivative of D-Ala2-Leu5-enkephalin was synthesized in a radioactive form, and the resulting compound (3H-DALECK) was used to label opioid receptors. 3H-DALECK binds with high affinity, specificity and saturability to rat brain membranes. The number of sites labeled is 130 fmoles/mg protein. Unlabeled opioids inhibited the binding of 3H-DALECK; etorphine and DAGO being most potent. A 10-fold preference for mu sites over delta was seen in site-specific competition experiments; while DALECK displayed low affinity for kappa sites of rat brain. DALECK irreversibly blocked a certain population of sites. Approximately 40% of 3H-DALECK binding at 15 min, and 60% at 60 min association time did not dissociate in the presence of a large excess of unlabeled DALECK and was resistant to washing. Autoradiography performed after SDS-PAGE revealed specific alkylation of proteins with molecular weight of 74, 65, 56, 43 and 34 kD. These results demonstrate the applicability of using 3H-DALECK to covalently label opioid receptors.     

Microinjection of oxytocin into limbic-mesolimbic brain structures disrupts heroin self-administration behavior: a receptor-mediated event?

The systemic injection of oxytocin (OXT) decreases the self-administration of heroin in heroin-tolerant rats. Since OXT-ergic binding sites are present in limbic and mesolimbic brain regions, the effects of intracerebral microinjections of OXT were investigated. In heroin-tolerant rats, the microinjection of OXT (2 ng) into the anterodorsal part of the nucleus accumbens or into the ventral hippocampus disrupted the self-administration of heroin. The effect of intrahippocampal microinjections lasted longer than that of intraaccumbens injections. The administration of N alpha-acetyl-(2-0-methyltyrosine)-oxytocin (ACME-OXT), an inhibitor of oxytocin receptors, prevented the disruptive effect of intrahippocampal OXT injections on heroin self-administration. It is concluded that limbic-mesolimbic brain structures have an essential role in the expression of the disruptive action of OXT on heroin self-administration. It appears that OXT-ergic binding sites mediate the effects of OXT.