Analysis of a continuous, aerobic, fixed-film bioreactor. I. Steady-state behavior

The analysis of a continuous, aerobic, fixed-film bioreactor is performed by simulating the behavior of penicillin production in a three-phase fluidized bed. Rigorous mathematical models are developed for a fluidized-bed fermentor in which bioparticles are fluidized by the liquid medium and air. The steady-state performance of the fluidized-bed reactor is appraised in terms of penicillin productivity and outlet concentration by considering the two extremes in contacting patterns, complete back-mix and plug flow, in the absence of a growing biofilm. The results show that the complete back-mix contacting pattern is preferred over that of plug flow due to the nature of the penicillin kinetic relationships. It is also shown that for the dual-nutrient (glucose and oxygen) penicillin reaction system the optimum biofilm thickness does not equal the penetration depth of a limiting nutrient, but depends upon the total reactor configuration.     

Monoclonal antibody against K562 cell line accelerates killing of the target cells by large granular lymphocytes

A monoclonal antibody (MoAb 11-4) was raised against K562, a human erythroleukemia cell line sensitive to natural killer cell-mediated cytotoxicity (NK-CMC). Immunological analysis revealed MoAb to be IgG_2b. Alone, the MoAb was not cytotoxic for K562 and did not bind to the effector cells, but the addition of this antibody to macrophage-depleted human peripheral blood lymphocytes increased killing of K562 in a 4-hr NK-CMC assay. The maximum increase in NK-CMC was observed when MoAb 11-4 was added to target cells prior to the formation of effector/target cell conjugates. This effect was dose dependent, was specific for K562, and, contrary to conventional antisera, occurred at very low concentrations of MoAb. When MoAb was added either to Percoll-purified large granular lymphocytes (LGL) or to LGL-depleted lymphocytes, only the latter demonstrated a significant increase in the killing of K562 in a 4-hr chromium release assay. Kinetics studies revealed that although the overall LGL-mediated lysis was only slightly increased at 4 hr, the maximum lytic activity was reached within 2 hr. These studies suggest that (1) human LGL and LGL-depleted cell populations bear Fc receptors for mouse IgG_2b and (2) although the cytotoxic activities of both cell populations are increased by treatment with MoAb 11-4, the kinetics of this increase are different.     

Molecular cloning and sequence analysis of cDNA for human transferrin

A cDNA clone for human transferrin was identified from a human liver cDNA library by pre-screening with different ss-cDNA probes against length-fractionated liver mRNAs, positive hybridization-selection and nucleotide sequence analysis. The insert was of 1 kb, encoding human transferrin from aminoacid 403 through the COOH terminus, with a 3' non coding region of 166 nucleotides. This insert hybridized with a single major mRNA species of about 2.4 kb and several genomic DNA restriction fragments. Hybridization of the Southern blots with different parts of the transferrin insert and at different stringences suggest that the various bands observed correspond to splice sites inside one gene rather than to hybridization to several related genes. Finally, a single or a low number of transferrin gene copies seem to exist in the human genome.     

New affinity adsorbents containing deoxycytidine, deoxyadenosine, or deoxyguanosine and their interactions with deoxynucleoside-metabolizing enzymes

3'-(4-Aminophenyl phosphate) derivatives of deoxycytidine (dCyd), deoxyadenosine (dAdo), and deoxyguanosine ( dGuo ) were synthesized. The inhibitory effects of these compounds on mammalian and bacterial deoxynucleoside kinases and several other deoxynucleoside-metabolizing enzymes were examined. The same derivatives were coupled to carboxyl-terminal Sepharose CL-6B (3-8 mumol of ligand/mL of gel), and each of the resulting affinity adsorbents was tested with various partially purified enzymes. Reasonable correlation between the inhibitory effect of a soluble deoxynucleoside 3'-phosphate diester and affinity of the corresponding Sepharose adsorbent for the enzyme was observed. Among the three dCyd kinases examined, only the bovine mitochondrial enzyme was adsorbed onto the dCyd-Sepharose column and eluted biospecifically by 1 mM dCyd (1400-fold purification). Its Ki toward the dCyd derivative was relatively low (1.1 mM), whereas no measurable inhibition was seen with mammalian cytosol or bacterial enzymes that did not stick to the column. The Ki of the dAdo derivative toward three dAdo kinases was more than 5 mM in each case, and none of these were retained by dAdo-Sepharose. Among the other dAdo-metabolizing enzymes examined, nucleoside phosphotransferase from barley (Ki = 1.2 mM) was adsorbed to dAdo-Sepharose at pH 5.0 and was biospecifically eluted with dAdo or AMP after suppressing ionic binding by adjusting the pH to 6.0 (480-fold purification to homogeneity). Mammalian mitochondrial dGuo kinase (beef liver) showed the lowest Ki (0.16 mM) among the enzymes tested and was biospecifically purified with dGuo -Sepharose (2800-fold purification).(ABSTRACT TRUNCATED AT 250 WORDS)     

Extreme temperatures and thermal tolerances for seedlings of desert succulents

Summary Extreme temperatures near the soil surface, which can reach 70°C at the main study site in the northwestern Sonoran Desert, markedly affect seedling survival. Computer simulations indicated that for the rather spherical barrel cactus Ferocactus acanthodes (Lem.) Britt. & Rose the maximum surface temperature decreased 8°C and the minimum temperature increased 3°C as the seedling height was increased from 1 mm up to 50 mm. Simulated changes in shortwave and longwave irradiation alone showed that shading could decrease the maximum temperature by about 5°C for the common desert agave, Agave deserti Engelm., and raise the minimum 1°C. Actual field measurements on seedlings of both species, where shading would affect local air temperatures and wind speeds in addition to irradiation, indicated that shading decreased the average maximum surface temperature by 11°C in the summer and raised the minimum temperature by 3°C in winter.Seedlings grown at day/iight air temperatures of 30°C/20°C tolerated low temperatures of about -7°C and high temperatures of about 56°C, as measured by the temperature where stain uptake by chlorenchyma cells was reduced 50%. Seedling tolerance to high temperatures increased slightly with age, and F. acanthodes was more tolerant than A. deserti. Even taking the acclimation of high temperature tolerance into account (2.7°C increase per 10°C increase in temperature), seedlings of A. deserti would not be expected to withstand the high temperatures at exposed sites, consistent with previous observations that these seedlings occur only in protected microhabitats. Based primarily on greater high temperature acclimation (4.3°C per 10°C), seedlings of F. acanthodes have a greater high temperature tolerance and can just barely survive in exposed sites. Wide ranges in photoperiod had little effect on the thermal sensitivities of either species. When drought increased the chlorenchyma osmotic pressure from about 0.5 MPa to 1.3 MPa, seedlings of both species became about 2°C less tolerant of high temperatures, which would be nonadaptive in a desert environment, and 2°C more tolerant of low temperatures, which also occurs for other species.In conclusion, seedlings of A. deserti and F. acanthodes could tolerate tissue temperatures over 60°C when acclimated to high temperatures and below -8°C when acclimated to low temperatures. However, the extreme environment adjacent to desert soil requires sheltered microhabitats to protect the plants from high temperature damage and also to protect them from low temperature damage at their upper elevational limits.     

Productivity of Agave deserti: measurement by dry weight and monthly prediction using physiological responses to environmental parameters

Summary An environmental productivity index based on physiological responses to three environmental variables was used to predict the net productivity of a common succulent perennial of the Sonoran Desert, Agave deserti, on a monthly basis. Productivity was also independently measured in the field from dry weight changes. The index was based on soil water availability, day/night air temperatures, and photosynthetically active radiation (PAR), which were individually varied in the laboratory and the effect on net CO₂ uptake by the leaves determined. From monthly precipitation, temperature, and PAR at the field site together with the responses measured in the laboratory, an index (maximum value of unity) was assigned to each of these three environmental variables and their product was termed the environmental productivity index. This index indicates the fraction of maximal CO₂ uptake expected in the field for each month (well-watered A. deserti assimilated 285 mmol CO₂ m^-2 leaf area day^-1 at PAR saturation and optimal day/night temperatures of 25° C/15° C). The dry weight analysis was based on the monthly unfolding of new leaves from the central spike of the rosette and their seasonal increase in dry weight, which were determined in the field. The production of new leaves was highly correlated with the environmental productivity index (r²=0.93), which in turn was highly correlated with the water status index (r²=0.97). After correction for respiration by folded leaves, stem, and roots, plant productivity predicted by the average environmental productivity index (0.36) over a wet June-to-October period agreed within 4% with the productivity based on the conventional dry weight analysis. The net productivity of A. deserti over this 5-month period was 0.57 kg m^-2 ground area (5.7 Mg ha^-1), a large value for a desert CAM plant. The environmental productivity index proposed here may provide a reliable means for predicting net productivity on a monthly basis, which may be particularly useful for species in relatively variable environments such as deserts.     

Increased acidic phospholipids in rat brain membranes after chronic ethanol administration

Two types of plasma membranes isolated from rat brain cortex were used to study the membrane-perturbing properties of ethanol. Rats administered ethanol in the form of a liquid diet showed an increase in levels of phosphatidylserines, phosphatidylinositols and phosphatidic acids as compared to controls. The results present evidence that chronic ethanol treatment results in an increase in the acidic phospholipids in brain membranes. This type of membrane modification may have important implications for the function of membrane transport enzymes such as (Na+, K+)-ATPase, which also increases in activity upon chronic ethanol administration.     

An electrogenic proton pump associated with the Golgi apparatus of mouse liver driven by NADH and ATP

Golgi-apparatus membranes, isolated from mouse liver, pump protons inwards, when supplied with NADH or ATP. The acidification of Golgi-apparatus cisternae and vesicles was detected with neutral red, a permeant dye, as a difference in absorbance at 550 nm minus that at 600 nm. The maximum rates detected with NADH and ATP were between 0.0006-0.0009 and 0.0030-0.0050 delta OD units/mg of protein/min, respectively, at pH 7.5. The outside buffer used was a bovine serum albumin suspension. The acidification of Golgi apparatus was inhibited from 45 to 100% by ionophores and from 22 to 100% by uncouplers. The results implicate both ATP and a redox system coupled to NADH oxidation in the acidification of Golgi-apparatus membranes.     

广谱肾综合征出血热病毒单克隆抗体的A35的生物学性状

具有中和及血凝抑制活性的、能和世界各地分离到的肾综合征出血热病毒(HFRSV)发生反应的、广谱的单克隆抗体(McAb),对HFRSV的诊断和分子生物学研究都有重要意义。 本文着重比较了HFRSV McAbA5、A19、A25-1、A25-7和A35的生物学性状,并观察了对感染动物的实验治疗效果。     

广西德峨苗族、彝族体质调查

对广西隆林县德峨乡男性22至60岁与女性20至60岁的576名苗族人(男395、女181)和178名彝族人(男88、女90)进行了活体观察与测量,计算出各项数据,总结德峨苗族、彝族的体质特征,并与国内一些民族相比较。