ER-to-Golgi carriers arise through direct en bloc protrusion and multistage maturation of specialized ER exit domains

Protein transport between the ER and the Golgi in mammalian cells occurs via large pleiomorphic carriers, and most current models suggest that these are formed by the fusion of small ER-derived COPII vesicles. We have examined the dynamics and structural features of these carriers during and after their formation from the ER by correlative video/light electron microscopy and tomography. We found that saccular carriers containing either the large supramolecular cargo procollagen or the small diffusible cargo protein VSVG arise through cargo concentration and direct en bloc protrusion of specialized ER domains in the vicinity of COPII-coated exit sites. This formation process is COPII dependent but does not involve budding and fusion of COPII-dependent vesicles. Fully protruded saccules then move centripetally, evolving into one of two types of carriers (with distinct kinetic and structural features). These findings provide an alternative framework for analysis of ER-to-Golgi traffic.     

Monitoring of etiological agents of acute enteric infections in the Moscow region

The fecal microflora of patients with acute enteric infections (AEI) has been examined on the territory of the Moscow region. The pathogens of high, moderate and low priority levels have been detected. As revealed in this study, shigellae, salmonellae, enteropathogenic and enteroinvasive Escherichia are the etiological agents of bacterial diarrheas on the territory of the Moscow region. The dynamics of the etiological agents of AEI in the region has been established.     

Dynamics of infection of Fringilla coelebs chaffinch nestlings with feather mites (Acari: Analgoidea)

A process of infecting the chaffinch nestlings Fringilla coelebs with three analgoid feather mites, Analges passerinus L., 1758, Monojoubertia microphylla (Robin, 1877), and Pteronyssoides striatus (Robin, 1977), commonly occurred on this bird species was investigated. 15 nests contained totally 65 nestlings, from 2 to 6 individuals in a brood, have been examined from the day of hatching till 11th day. Observations were held in the neighbourhood of the bird banding station "Rybachy" (Russia, Kaliningrad Province) in June of 1982. Number of mites on alive nestlings taken temporarily from their nest was counted by means of binocular lens under the magnification x12.5 and x25. The nestlings receive the mites from the chaffinch female during the night time, when the female sits together with the young birds and heats them. In the condition of this prolonged direct contact the mites migrate from the female onto the nestlings. As it was shown in our study of seasonal dynamics of mites on the chaffinch (Mironov, 2000), the chaffinch female only gives its mites to young generation and looses about three quarter of its mite micropopulation during the nesting period (June), hile in the chaffinch males the number of mites continues to increase during all summer. The infections with three feather mite species happen in the second part of the nestling's stay in the nest. The starting time of this process, its intensity, and sex and age structure of mite micropopulations on the nestlings just before their leaving the nest are different in the mite species examined. These peculiarities of feather mite species are determined by the biology of examined species, and first of all by their morphological characteristic and specialisation to different microhabitats, i.e. certain structural zones of plumage. Pteronyssoides striatus (Pteronyssidae) is rather typical mite specialised to feathers with vanes. In adult birds with completely developed plumage this species occupies the ventral surface of the big upper coverts of primary flight feathers. This species appears on the chaffinch nestlings in a significant number on 7th day. The mites occupy the basal parts of primary flight feathers represented in that moment by the rods only. They sit on practically open and smooth surface of this microhabitat, which is uncommon for them, because the vanes of the big upper coverts are not yet open and also represented by thin rods. During the period of the last 5 days (from 7 to 11th day) the mean number of mites per one nestling increases from 2.3 +/- 0.5 to 17.1 +/- 1.8 mites. Just before the day, when the nestling leave the nest, the tritonymphs absolutely predominate (82.4%) in the micropopulation of P. striatus. Analges passerinus (Analgidae) is specialised to live in the friable layer formed by numerous not-engaged thread barbles of the down feathers and basal parts of the body covert feathers. Mites have special hooks on legs used for hard attaching to the barbles and for fast moving in the friable layer of feathers. On the chaffinch nestlings, these mites appear usually on 8th day, when the rod-like body covert feathers begin to open on apices and form short brushes; however some individuals occur on the skin of nestlings even on 6th day. The mean number of mites per nestling on the 11th day reaches 16.5 +/- 1.4 individuals. The micropopulation of A. passerinus is represented on the nestlings mainly by the females (45.5%), tritonymphs (23.6%) and males (11.5%). Monojobertia microphylla (Proctophyllodidae) is a typical dweller of feathers with large vanes. Mites of this species commonly occupy the ventral surface of primary and secondary flight feathers and also respective big upper covert feathers of wings. M. microphylla appears on the nestlings in a significant number (7.1 +/- 1.2 mites) on 9th day, only when the primary flight feathers already have short vanes about 10 mm in length. In next three days the number of mites increases very fast and reaches on 11th day 60.3 +/- 5.7 mites per nestling. In the micropopulation of this species, the tritonymphs count 38.3%, and the quota of males and females is 25.3% each. The migration of this species goes most intensively, than in two other species. An analitic selection of logistic curves shows, that the increasing of mite number during the process of infection with three mite species may be most adequately described by the sigmoid curves with clearly recognizable levels of saturation, which can be theoretically reached. Indeed, the number of mite individuals being able to migrate onto the nestlings is limited by their number on a respective chaffinch female. In a contrast, the increasing of plumage indices, for instance the length of flight feathers, has almost linear character during the period of observation. The beginning of mite migration is determined by the development of respective microhabitats in the plumage of nestlings, or at least by the development of certain structure elements of plumage, where mites are able to attach for a while, before that moment, when the nestlings will develop the plumage completely and begin to fly. In three mite species examined, the process of infection was performed by older stages, namely by the imago and/or tritonymphs. This can be explained by two reasons. On the one hand, the older stages are most active in their movement, resistible and able to survive successfully on new host individuals. On the other hand, the older stage are ready for the reproduction or will be ready after one moulting. The older stages of mites can quickly create a large and self-supporting micropopulations on the birds, therefore this strategy ensures a successful subsequent existence of the parasite species. In cases, when mites (A. passerinus, M. microphylla) migrate into the respective microhabitats structurally corresponding to their normal microhabitats on adult birds, the micropopulations of these mite species include a significant or dominant quota of females and males. When the normal microhabitat is not yet formed, feather mites migrate into neighboring structure elements of plumage, where they can survive and wait for the development of normal microhabitat, to which they are well adapted. Therefore, in the case of P. striatus, its micropopulations on the chaffinch nestlings are represented mainly by the tritonymphs.     

Performance-Guarantee Gene Predictions via Spliced Alignment

An important and still unsolved problem in gene prediction is designing an algorithm that not only predicts genes but estimates the quality ofindividualpredictions as well. Since experimental biologists areinterested mainly in the reliability of individual predictions (rather than in the average reliability of an algorithm) we attempted to develop a gene recognition algorithm that guarantees a certain quality of predictions. We demonstrate here that the similarity level with a related protein is a reliable quality estimator for thespliced alignmentapproach to gene recognition. We also study the average performance of the spliced alignment algorithm for different targets on a complete set of human genomic sequences with known relatives and demonstrate that the average performance of the method remains high even for very distant targets. Using plant, fungal, and prokaryotic target proteins for recognition of human genes leads to accurate predictions with 95, 93, and 91% correlation coefficient, respectively. For target proteins with similarity score above 60%, not only the average correlation coefficient is very high (97% and up) but also the quality of individual predictions isguaranteedto be at least 82%. It indicates that for this level of similarity the worst case performance of the spliced alignment algorithm is better than the average case performance of many statistical gene recognition methods.     

Molecular cloning of the structural genes of the Escherichia coli deo-operon in plasmid RSF2124]

A specialized phage lambda ddeo carrying the deo operon of Escherichia coli is analyzed by exposing the DNA to the specific restriction endonucleases EcoRI and BamHI. Using the lambda ddeo DNA fragment, obtained by digestion with BamHI and plasmid RSF2124 as a vehicle, the hybrid plasmid pAM1 carrying all the genes of the deo operon is constructed and cloned in E. coli cells. It is shown that the activity of thymidine phosphorylase in the strain AM061, which contains hybrid plasmid pAM1 is 30-fold greater than that in strains of E. coli with chromosomal localization of the deo operon.     

Effect of mutations for adenylate cyclase (cya) and the cyclic adenosine monophosphate receptor protein (cgp) on the gene expression of nucleoside catabolism in Escherichia coli]

The effect of cya and crp mutations on the expression of the activity of nucleoside catabolizing genes has been studied in Escherichia coli. It is found that cya and crp mutants lose their ability to grow on nucleosides as carbon sources in spite of the preservation of the basal levels of nucleoside catabolizing enzymes, found in cell-free extracts of cya and crp mutants. It is shown that cya and crp mutations completely release the influence of the regulatory gene cytR on the activity of uridine phosphorylase (udp gene) and thymidine phosphorylase (tpp gene). On this ground it is assumed that the cytR gene product acts at the level of promotors of the corresponding structural genes, causing their insensitivity to the positive action of cAMP--CRP complex. The same data concerning the effect of cya and crp mutations on cytR regulation have been reported [8], but these authors favoured the hypothesis that the cytR gene product is a repressor protein, which binds to the specific operator.     

Study of the lympho- and hemomicrocirculatory bed of lymph nodes by scanning electron microscopy

The spatial interrelation of the lymphatic and blood beds has been studied in the lymph node together with its stromal and lymphoid elements, using scanning electron microscopy of corrosive casts and native preparations. There is a great variety of pathways for lymph transport and blood vessels in dependence of their localization in the lymph node. Of a special interest are the pathways of lymphocytes migration across the walls in the cortical and medullary sinuses and in the postcapillary venules, as well as participation of the reticular tissue in the lymph node immune reactions.