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Brief review of main conceptions of Yu. S. Balasov in fundamental parasitology: types of host-parasite relations, evolution, transmissive infections, econiches, population structure, parasite communities.

Postembryonic development of Paraphelenchus myceliophthorus has been studied. The first molt takes place inside the egg-shell; outside the latter 3 molts were revealed, dividing 2nd, 3rd, 4th stage juveniles, and the adults. Descriptions of morphology of all juvenile stages were given, as well as morphology of all molting juveniles and adults. Stages of development differ in the genital primordium structure and in body length. In juveniles of 3rd and 4th stage the sex of juvenile can be distinguished--male juveniles have cloacal primordium, whereas female juveniles have vulval primordium. In male 3rd stage juveniles the large germinal cell is situated in the posterior part of the genital primordium, whereas female 3rd stage juvenile has the large germinal cell in the anterior part of the genital primordium. Adults differ from juveniles in the presence of copulative structures--vulva in adult female and spicules in male. The adult male has caudal alae (bursa) in the form of lateral cutucular folds and 4 pairs of caudal papillae, one preanal pair at mid-spicule level and 3 postanal pairs--p1 situated just posterior to cloacal opening, p2 at mid tail, p3 and p4 on the tail terminus. An unpaired papilla is also present just anterior to the cloacal opening. Gubernaculum is present. The tracery inner tail framework supporting the spicules has been described. In females 2 pairs of tail tip tuberculi are present, and 2 ventral ones are distinctly longer than 2 dorsal ones. These tuberculi correspond to p3 and p4 pairs of papillae in male and are homologous to tail tip papillae of the Aphelenchus females, which earlier were considered to be phasmids. These 4 tuberculi are joined with 4 one-celled glands of tail terminus.

Four new records of Bursaphelenchus mucronatus in saw-timbers from the Asian part of Russia (Irkutsk Oblast and Krasnoyarsk Krai, larch, pine and spruce wood) intercepted in St. Petersburg, are described, measured and illustrated. The diagnosis of B. mucronatus is amended and its relationships within species group xylophilus, and especially its differences from a quarantine pests B. xylophilus, are given. The record of the B. mucronatus transition from Asiatic into European part of Russia suggests possible transcontinental way of the xylophilus group penetration with saw-timber. Pest risk analysis of B. xylophilus for the European part of Russia is discussed in scope of the global warming.

Postembryonic development of Bursaphelenchus mucronatus has been studied. First molt takes place within the egg-shell, and three subsequent molts after hatching. Structure of all juvenile stages are described, as well as molting juveniles and adults. Juvenile stages differ in genital primordium structure, copulatory structures primordial and the body length. In juveniles of 3rd and 4th stage the sex of juvenile was distinguished: male juveniles have cloacal primordium, whereas female juveniles have vulval primordium. Adults differ from juveniles in presence of vulva in females and spicules in males. The key to identify juvenile stages and their sex is given. Male has the terminal bursal flap and 3 pairs of iail papillae: p1 anadanal; p2 and p3 at the bursal flap base: p2 close to mid-line of the ventral body surface, p3 located laterally to p2 at the same level. Unpaired papilla is present on the upper cloacal lip, on the ventral mid-line.

Phylogenic models for each aphelenchid family and phylogeny of the order Aphelenchida as a whole were developed on the base of detailed comparative morphological and bionomical analysis of the order. Bionomical and morphological characters having a phylogenetic significance were selected. Classification proposed by Hunt, 1993 was used as the starting-point of the study. Life cycles and their evolution in Aphelenchida were analyzed on the base of phylogenetic trees. It is concluded, that aphelenchid ancestors combined mycophagy, plant parasitic, and partly predaceous feeding. Relations of the primitive Aphelenchida with their symbionts developed from the spots of the fungal organic matter decomposition in the "nema- tode-fungi" associations, followed by a transition to the temporary endoparasitic habit omitting ectoparasitism. With a complication of the nematodes' life cycles, the insect vector (detritophagous or pollinator) transformed into the real insect host of the parasitic nematode in the 2-host life cycle (with the plant and insect hosts) or in the obligate 1-host entomoparasitic life cycle of the aphelenchid nematodes. Specialization of the aphelenchid life cycles to insect vectors followed two main ways. In the first way, the resistant to unfavorable environmental conditions nematode juveniles, known already for the primitive aphelenchids transformed into dispersal juveniles, and later into parasitic juveniles. In the second evolution line the dispersal function were laid on inseminated but non-gravid (not egg-producing) females. Both above-mentioned trends of parasitic specialization were arisen independently in different phylogenetic lines of the Aphelenchida. In each line of the parasitic development in different nematode families, the highly specialized ectoparasites, as well as endoparasites on insects, were formed. In the evolution of life cycle of parasitic nematodes, a tendency to decrease the body size took place. The function of dispersion shifted to more junior juvenile stage (the first line of specialization), or body sizes of non-gravid females and males copulated with the latter become smaller (second specialization line, till the development of dwarf males and location of the males and small inseminated non-gravid females in the uterus of gravid nematode female). The hypothetic fundamental model of the parasitic cycles' specialization in the order Aphelenchida was developed, basing on the comparison of known life cycles in different phylogenetic lines within aphelenchid families. The conception of the geographic origin and historic dispersal of the order Aphelenchida was proposed. The origin of the superfamily Aphelenchoidoidea and order Aphelenchida as a whole probably took place in eastern areas of Gondwana (parts of which are recently Hindustan, Indo-Malaya, Australia and Antarctica), presumably in the Devonian period. When the Gondwana and Laurasia paleocontinents were joined into Pangea in Carbon period, aphelenchids dispersed in the Laurasian part of Pangea. Endemism of the advanced entomophilic ectoparasitic Acugutturidae indicates on the secondary hotbed of speciation in Caribbean area. Development of the anhydrobiotic adaptations in the Aphelenchida promoted their successful invasion in the cold regions of Holarctic. Another important adaptations was the transformation of the initially resistant nematode life cycle phase into the dispersal phases vectored by insects.

The amended diagnosis of the genus Pratylenchoides and list of its valid species with synonyms are given. All the efficient diagnostic characters are listed. Modern taxonomic standard for the description of Pratylenchoides species is proposed; it may be used also in taxonomic databases. Tabular and text keys for all species of the genus are given. Five following groups are considered within the genus Pratylenchoides. The group arenicola differs from other groups in the primitive adanal bursa type; the groups magnicauda, crenicauda, ritteri, and megalobatus differ from each other in the position of cardium along the body axis in relation to the pharyngeal gland nuclei, pharynx types are named according to the stages of its evolution from the primitive tylenchoid pharynx (cardium situated posteriorly) to the advanced hoplolaimoid one (cardium situated anteriorly). Diagnoses and species compositions of the groups are given. Basing on the matrix of species characters, the dendrogram has been generated for all species of Pratylenchoides and for all characters (UPGMA, distance, mean character difference, random, characters ordered). Taking in view that the PAUP software gives equal weights to all characters, including the most important ones which define the prognostic species groups, the separate dendrograms for each prognostic species group were generated using the same above mentioned tree parameters. On the base of the records of Pratylenchoides species the matrices of plant host ranges, geographic distribution, and preferred soil-climatic conditions were developed. The dendrograms of the faunal similarities were generated using these matrices, with conclusions on a possible origin and evolution of the genus. The genus evolved from the flood lands with swampy soils and prevalence of dicotyledons (herbaceous Lamiaceae and woody Salicaceae families) to the forest mainland communities with balanced humidity and predominance of herbaceous Poaceae and Fabaceae with woody Fagaceae, Betulaceae, and Oleaceae. The leading factor of the evolutional adaptation to soil-climatic conditions was the factor of humidity, but its significance gradually decreased with the host change to more advanced plant taxa adapted to the communities with more dry balanced humidity. The genus took its origin on the south shores of Laurasia in the Cainozoe. Later, when Hindistant and Arabian Peninsula joined with Laurasia creating the Himalayas barrier, the Pratylenchoides spp. distributed by two branches: the northern one moved into Central Asia, East Europe and North America, and the south branch came into Indo-Malaya, West Asia and the north of Africa. The remnants of the ancient species groups remain in West Europe and East Asia. In the North America the genus gave an origin to its sister genus Apratylenchoides, which spread to the south up to Antarctica; another advanced branch spread in the North America reaching Alaska.

The use of a present-day method of statistical investigation allowed to present the variety of pathological changes in acute cholecystitis in a parametric form, i.e. as a scale of scores. The scale allows determination of comparative severity of one or another changes characteristic of acute cholecystitis in the concrete patient. The correlation analysis as well as scores assessment show a substantial importance of the functional ability of detoxicating mechanisms for the characteristic of the degree of pathological changes.

The authors made an analysis of early operations on 6076 patients. This tactics used in 84.3% of the patients allowed to reduce postoperative lethality up to 2.5%.

Morphogenesis of the genital system of 14 species of nematodes of the superfamily Tylenchoidea was studied. The evolution of the genital system of females in the superfamily was considered. The initial type for the group is a paired gonade of the females. In different families the reduction of the hind branch of the gonade proceeds in parallel. During ontogenesis the development of the posterior part of the trophicogenital department and the gonade branch restrains. In the family Pratylenchidae this phenomenon is associated with the shortening of the body during the transition to endoparasitism; in the family Tylenchidae the phenomenon is connected with the acquiring of the streamline form suitable for living in humid biotopes. In the family Anguinidae takes place the hypertrophy of the female genital system connected with the transition to the cavitary endoparasitism. A new technique for making preparations of nematodes is suggested.

The tactics of early operations for acute cholecystitis in patients with diabetes mellitus gives substantially better results of surgery. In the recent years the incidence of complications in this group of patients has been 20.3%, lethality--6.3%. Control of the carbohydrate metabolism must be made at short terms. It is the operation in combination with the rational insulin therapy which gives the correction of the carbohydrate metabolism.

An investigation of specific course of the disease in 911 patients operated upon for acute cholecystitis with bilirubinemia has shown that mechanical jaundice resulting from choledocholithiasis takes place in a third of the patients. Obstruction of the bile duct was confirmed in 27.1% of the patients during cholangiography. Prevalence of a number of factors was noted indicating of a toxic lesion of the liver (destructive forms of acute cholecystitis in 81.0% of the patients, higher level of bilirubinemia in long terms of the disease, the presence of coexistent pancreatitis in 30.5%, cholangitis--in 39.3%). An investigation of 207 bioptates of the liver in acute cholecystitis has revealed fatty degeneration of hepatocytes in 56.5%, pericholangitis--in 43.0%, cholestasis--in 21.3% of the cases. The cause of jaundice in acute cholecystitis mainly is an alteration of the hepatic cells due to pyo-resorptive intoxication manifested as cholestasis and hepatitis.