Observations on the initiation and stimulation of oviposition of theVarroa mite

FemaleVarroa mites were collected from adult bees and were classified as swollen or not swollen. After introduction of these mites into recently sealed worker brood cells the average number of offspring of reproducing swollen mites was similar to that of naturally invaded mites, but the non-swollen mites produced a significantly lower number of offspring. This suggests that the oviposition of adult mites is stimulated by a preceding stay on adult bees. When (non-swollen) mites collected from brood cells were kept for 35 days in Eppendorf test tubes containing a larva or a pupa, their reproduction was similar to that of swollen mites.Contact of young mites, collected from brood cells, with adult bees was not essential for the initiation of oviposition. However, the number of offspring of reproducing mites, even after a third or fourth introduction into brood cells, was as a rule lower than that of mites that had been in contact with adult bees.The period of artificial introduction into sealed brood cells proved to be essential for subsequent reproduction. When introduced 48–52 h or 72–76 h after cell sealing, the mites did not produce eggs. When introduced 0–4 h after cell sealing a high percentage of the mites reproduced. Contact of the mites with a spinning larva seems necessary for initiation of oviposition.     

Countercurrent multistage fluidized bed reactor for immobilized biocatalysts: II. Operation of a laboratory-scale reactor

In Part I of this series,(1) we derived a model and made simulations for a multistage fluidized bed reactor (MFBR). It was concluded that the MFBR can be an attractive alternative for a fixed bed reactor when operated with a deactivating biocatalyst. In Part II of this series, the design of a laboratory-scale MFBR and its evaluation to investigate the practical feasibility of this reactor type, will be described. Experiments with a duration as long as 10 days were carried out successfully using immobilized glucose isomerase as a model reaction system. The results predicted by the model are in good agreement with the measured glucose concentration and biocatalyst activity gradients, indicating perfect mixing of the particles in the reactor compartments.The diameters of the biocatalyst particles used in the experiments showed a large spread, with the largest being 1.7 times the smallest. Therefore, an additional check was carried out, to make sure that the particles were not segregating according to size. Particles withdrawn from the reactor compartments were investigated using an image analyzer. Histograms of particle size distribution do not indicate segregation and it is concluded that the particles used have been mixed completely within the compartments. As a result, transport of biocatalyst is nearly plug flow.     

Some features of feeding,respiration and energy conversion of Dapnia Magna

Some results of studies with Daphnia magna are presented. These results can be used as background information for toxicologists, but the techniques referred to might well be used for toxicity tests. Daphnia magna is a filter-feeder. With the Coulter Counter it was shown that the feeding mechanism is aselective for size of the food particles. It was also shown that algal cells can pass the gut of Daphnia magna several times before being completely digested. The uptake of food is proportional to the food concentration up to a critical concentration. Above this concentration the food uptake is constant. Respiration is also dependent on the food concentration, and has a maximum value at food concentrations near the critical concentration of the feeding process. Growth efficiency is independent of the food concentration. The effect of temperature on the feeding process is different for low and high food concentrations. Growth efficiency is maximal at 10°C and above 22°C growth efficiency was negative, which means that the population cannot survive under the experimental conditions used, at temperatures above 22°C.     

Spontaneous insertion of plant plasma membrane (H+)ATPase into a preformed bilayer

Summary The purified (H⁺ATPase from corn roots plasma membrane inserted spontaneously into preformed bilayer from soybean lipids. The yield of the protein insertion, as measured from its H⁺-pumping activity, increased as a function of lipids and protein concentrations. In optimum conditions, all the (H⁺)ATPase molecules were closely associated with liposomes, exhibiting a high H⁺-pumping activity (150,000% quenching· min^–1·mg^–1 protein of the probe 9-amino-6-chloro-2-methoxyacridine). The insertion was achieved within a few seconds. No latency of the (H⁺)ATPase hydrolytic activity was revealed when lysophosphatidylcholine was added to permeabilize the vesicles. This indicated that the (H⁺)ATPase molecules inserted unidirectionally, the catalytic sites being exposed outside the vesicles (inside-out orientation), and thus freely accessible to Mg-ATP. The nondelipidated (H⁺)ATPase could also functionally insert into bilayer from PCPEPG or PCPEPI, due to the presence of both hydrophobic defects promoted by PE, and negative phospholipids specifically required by the (H⁺)ATPase from corn roots. The detergent octylglucoside facilitated the delipidated (H⁺)ATPase reinsertion probably by promoting both a proper protein conformation and hydrophobic defects in the bilayer. Lysophosphatidylcholine facilitated the delipidated protein insertion only when hydrophobic defects were already present, and thus seemed only capable to ensure a proper protein conformation     

Novel Surface Display System for Proteins on Non-Genetically Modified Gram-Positive Bacteria

A novel display system is described that allows highly efficient immobilization of heterologous proteins on bacterial surfaces in applications for which the use of genetically modified bacteria is less desirable. This system is based on nonliving and non-genetically modified gram-positive bacterial cells, designated gram-positive enhancer matrix (GEM) particles, which are used as substrates to bind externally added heterologous proteins by means of a high-affinity binding domain. This binding domain, the protein anchor (PA), was derived from the Lactococcus lactis peptidoglycan hydrolase AcmA. GEM particles were typically prepared from the innocuous bacterium L. lactis, and various parameters for the optimal preparation of GEM particles and binding of PA fusion proteins were determined. The versatility and flexibility of the display and delivery technology were demonstrated by investigating enzyme immobilization and nasal vaccine applications.     

On the origin of the limited control of mitochondrial respiration by the adenine nucleotide translocator

A thermodynamic control theory previously developed has been applied to mitochondrial oxidative phosphorylation with emphasis on the role of delta microH and coupling and within the paradigm of delocalized chemiosmotic coupling. The basis for the observed distribution of flux control over the participating enzymes is shown to lie in the relative magnitudes of so-called delta microH elasticity coefficients, i.e., the delta microH dependencies of the different mitochondrial processes. In particular the relatively strong delta microH dependence of mitochondrial respiration is responsible for the significant role of the adenine nucleotide translocator in the control of oxidative phosphorylation. Uncoupling decreases the control exerted by this translocator on respiration but increases that exerted on phosphorylation.     

Alterations of plasma lipids in mice via adenoviral-mediated hepatic overexpression of human ABCA1

ATP binding cassette transporter A1 (ABCA1) is a widely expressed lipid transporter essential for the generation of HDL. ABCA1 is particularly abundant in the liver, suggesting that the liver may play a major role in HDL homeostasis. To determine how hepatic ABCA1 affects plasma HDL cholesterol levels, we treated mice with an adenovirus (Ad)-expressing human ABCA1 under the control of the cytomegalovirus promoter. Treated mice showed a dose-dependent increase in hepatic ABCA1 protein, ranging from 1.2-fold to 8.3-fold using doses from 5 x 108 to 1.5 x 109 pfu, with maximal expression observed on Day 3 posttreatment. A selective increase in HDL cholesterol occurred at Day 3 in mice treated with 5 x 108 pfu Ad-ABCA1, but higher doses did not further elevate HDL cholesterol levels. In contrast, total cholesterol, triglycerides, phospholipids, non-HDL cholesterol, and apolipoprotein B levels all increased in a dose-dependent manner, suggesting that excessive overexpression of hepatic ABCA1 in the absence of its normal regulatory sequences altered total lipid homeostasis. At comparable expression levels, bacterial artificial chromosome transgenic mice, which express ABCA1 under the control of its endogenous regulatory sequences, showed a greater and more specific increase in HDL cholesterol than Ad-ABCA1-treated mice. Our results suggest that appropriate regulation of ABCA1 is critical for a selective increase in HDL cholesterol levels.     

Differential use of zooplankton prey by Ancient murrelets and Cassin's auklets in the Queen Charlotte Islands

The distribution at sea and the food of two similar sized plankton-feedingalcids were examined during the 1981 breeding seasons in thenorthwestern Queen Charlotte Islands, British Columbia. Thetwo alcids, the Ancient murrelet (Synthliboramphus antiquus)and the Cassin's auklet (Prychoramphus aleuticus) have differentchick-rearing strategies. Both species fed predominantly atthe shelf break, although the Cassin's auklet also foraged overseamounts. The feeding distributions of the species appear tobe related to those of their prey. Zooplankton sampling indicatedthat each alcid selects a small and different portion of thezooplankton available in surface waters. The Ancient murrelet'smain foods were euphausiids (Thysanoessa spinifera and Euphausiapacifica) and larval and juvenile fishes. The Cassin's aukletchicks fed chiefly on calanoid copepods (Neocalanus cristatus).euphausiids (mostly Thysanoessa longipes in 1981, but in otheryears also Thysanoessa spinifera), and larval and juvenile fishes.The Cassin's auklets took smaller prey than the Ancient murrelet.Differences in the diets of the two alcid species were associatedwith differences in morphology and chick-rearing strategies.