PubMed Health⌕ Search

Biomedical subjects

D Andreev

Publications and source records attributed to D Andreev.

At least 19 recordsLinked to original sources
PubMed2003

Localization and distribution of laminin in the basal lamina of certain mechanoreceptors--an immunogold study.

The applied immunogold cytochemical technique in investigating the cytologic distribution of the laminin (LAM) molecule in the capsulated Pacinian and Herbst mechanoreceptors shows the presence of LAM around most elements of the receptor structures. The LAM immunoreactivity (LAM-IR) is best expressed in the vicinity of the perineural capsule cells of both receptor types, where it is primarily concentrated around the perinuclear regions as well as the cytoplasmic lamellae. Such a localization overlaps with the already known ultrastructural localization of a basal lamina (BL) around these cells. Laminin immunoreactivity is less well expressed around the modified Schwann cells. Even in these cells, however, there is an apparent immunoreaction around the cytoplasmic lamellae regardless of the lamellar location. In both receptor types, there is no LAM-IR in the cells of the subcapsular space. Of particular significance we consider the localization of gold particles (respectively the presence of a BL) between the innermost lamellae of the modified Schwann cells and the non-myelinated part of the receptor nerve fiber and their endings, as well as around the axoplasmic protrusions of the nerve endings. We discuss the role of the BL and LAM in the investigated rapidly adapting mechanoreceptors and their trophic influence upon the sensory regions. We also assume the arresting and selective effect of these membranes in building up the ion channels of the axolemma which probably has a certain importance in mechanotransduction.

Animals↗
PubMed1999

Multiple origins of cyclodiene insecticide resistance in Tribolium castaneum (Coleoptera: Tenebrionidae).

The number of origins of pesticide resistance-associated mutations is important not only to our understanding of the evolution of resistance but also in modeling its spread. Previous studies of amplified esterase genes in a highly dispersive Culex mosquito have suggested that insecticide resistance-associated mutations (specifically a single-gene duplication event) can occur a single time and then spread throughout global populations. In order to provide data for resistance-associated point mutations, which are more typical of pesticide mechanisms as a whole, we studied the number of independent origins of cyclodiene insecticide resistance in the red flour beetle Tribolium castaneum. Target-site insensitivity to cyclodienes is conferred by single point mutations in the gene Resistance to dieldrin (Rdl), which codes for a subunit of a gamma-aminobutyric acid (GABA) receptor. These point mutations are associated with replacements of alanine 302 which render the receptor insensitive to block by the insecticide. We collected 141 strains of Tribolium worldwide and screened them for resistance. Twenty-four strains contained resistant individuals. After homozygosing 23 of these resistance alleles we derived a nucleotide sequence phylogeny of the resistant strains from a 694-bp section of Rdl, encompassing exon 7 (which contains the resistance-associated mutation) and part of a flanking intron. The phylogeny also included six susceptible alleles chosen at random from a range of geographical locations. Resistance alleles fell into six clades and three clades contained both resistant and susceptible alleles. Although statistical analysis provided support at only the 5-6% level, the pattern of variation in resistance alleles is more readily explained by multiple independent origins of resistance than by spread of a single resistance-associated mutation. For example, two resistance alleles differed from two susceptible alleles only by the resistance-associated mutation itself, suggesting that they form the susceptible ancestors and that resistance arose independently in several susceptible backgrounds. This suggests that in Tribolium Rdl, de novo mutations for resistance have arisen independently in several populations. Identical alleles were found in geographically distant regions as well, also implying that some Rdl alleles have been exported in stored grain. These differences from the Culex study may stem both from differences in the population genetics of Tribolium versus that of mosquitoes and differences in mutation rates associated with point mutations versus gene duplication events. The Tribolium data therefore suggest that multiple origins of insecticide resistance (associated with specific point mutations) may be more common than the spread of single events. These findings have implications for the way in which we model the evolution and spread of insecticide resistance genes and also suggest that parallel adaptive substitutions may not be uncommon in phyletic evolution.

Animals↗
PubMed1998

Lack of nucleotide variability in a beetle pest with extreme inbreeding.

The coffee berry borer beetle Hypothenemus hampei (Ferrari) (Curculionidae: Scolytinae) is the major insect pest of coffee and has spread to most of the coffee-growing countries of the world. This beetle also displays an unusual life cycle, with regular sibling mating. This regular inbreeding and the population bottlenecks occurring on colonization of new regions should lead to low levels of genetic diversity. We were therefore interested in determining the level of nucleotide variation in nuclear and mitochondrial genomes of this beetle worldwide. Here we show that two nuclear loci (Resistance to dieldrin and ITS2) are completely invariant, whereas some variability is maintained at a mitochondrial locus (COI), probably corresponding to a higher mutation rate in the mitochondrial genome. Phylogenetic analysis of the mitochondrial data shows only two clades of beetle haplotypes outside of Kenya, the proposed origin of the species. These data confirm that inbreeding greatly reduces nucleotide variation and suggest the recent global spread of only two inbreeding lines of this bark beetle.

Animals↗
PubMed1994

Tubular networks in soleus muscle fibers of the rat following tenotomy. I. Spatial organization.

Complex systems of tubules, 30-40 nm in diameter, were observed in myofibers of the soleus muscle of Wistar rats following experimental transection of the Achilles tendon. The appearance of these systems varied remarkably, depending upon the plane of sectioning. The spacial arrangement of the tubules was reconstructed by comparing several sections through individual systems. Such reconstructions revealed that they are networks of tubular elements arranged in an hexagonal pattern. A three-dimensional wire model was prepared, illustrating the spatial organization of the tubular systems. The model consists of four groups of lattices with a honeycomb-like arrangement. The lattices of each group are parallel to one another, and intersect those of the other groups at an inclination of 60 degrees.

Animals↗
PubMed1985

[Factors affecting the antigenicity of exogenous insulin in diabetics].

The antigenic properties of insulin and the effect of additional factors on them, HL-A-phenotype including were studied under different conditions in 3 groups of diabetic patients (I--71 patients treated with insulin, II--48 diabetic patients--never treated with insulin and III--51 diabetics, treated at least 6 months with conventional insulin and later treated with monocomponent insulin "Actrapid"). In some other experiments, making use of 7 groups guinea pigs, the antigenicity of different trade insulin preparations was tested. The antibody titre was assessed by the insulin-binding serum capacity, incubated with 131I-insulin. The authors established a significant dependence of antibody titre on insulin during insulin treatment and insignificant--with the age of the patients, duration of insulin treatment and HL-A phenotype. The last correlation with HLA-phenotype B 15 was highly significant. A reduction of antibody titre was established after changing from conventional to highly-purified monocomponent insulin preparation and anew elevation of titre with the resumed treatment with non-purified insulin forms according to special ways. All insulin preparations, that the separate groups of guinea pigs were injected, led to significant increase of antibody titre in the experimental animals. The better purified of them, however, as "insulin Comb" and Bulgarian "neutral porcine insulin"--Pharmachim, are less antigenic. A treatment with highly purified preparations is recommended for the diabetic patients with HLA-phenotype B 15.

Adult↗
PubMed1984

[Comparison between the incidence of diabetic macroangiopathy in a group of diabetics from Bulgaria and from 13 other countries].

A Bulgarian team, within the frames of a multinational study on diabetic vascular disease, sponsored by WHO, studied a group of 473 diabetic patients by the inquiry method and by the determination of blood cholesterin and creatinine and urine albumin. The results were compared with those of the whole group (6695 patients from 14 countries) and with each national group separately. A higher percentage of insulin-treated patients was established in the Bulgarian group as compared with the whole group, fewer hypertonics, lower mean cholesterol values, a little higher average body weight and considerably lower percentages of smokers. The various forms of macroangiopathy among the Bulgarian group proved to be in percentages, approaching the average percentages for the whole group or little lower than them (e.g. for the category "probable infarctions" and "cerebral hemorrhages"). Only for the category "IHD" the affection percentage among the Bulgarian group significantly surpassed that of the whole group. Since the Bulgarian group, as regards the possible risk factors, is in a more favourable condition, the higher IHD percentage is admitted to be due to the circumstances that patients with graver states have been included in the group. That is suggested by the higher percentage of patients (52%), insulin-treated. The severity of diabetes is concluded to be a significant factor in the development of macroangiopathy.

Adult↗
PubMed1983

[The organogenetic development of the human extensor hallucis longus muscle].

The organogenetic investigations on the human crural and foot musculature give only a general idea for the development of the m. extensor hallucis longus (Schomburg 1900; Bardeen 1907), but it is not possible to understand the sequence of the changes of the primordium of this muscle during its morphogenesis. To the best of our knowledge, so far no interpretation of these changes is known, although it is of great significance to the evolutionary myology. Therefore, it seemed reasonable to us to carry out an investigation on the organogenesis of the m. extensor hallucis longus from the evolutionary myology point of view, using the results of previous detailed comparative-anatomical study of the same muscle. The basis of such an investigation was well-grounded a few years ago (Kaneff 1977).

Gestational Age↗
PubMed1982

[Effect of dietetic fruit products prepared with sorbitol and pectin on the blood sugar and insulin levels in diabetic patients].

The effect of four kinds dietetic fruit products, sweetened by Sorbitol (pectin nectar, apricot nectar, apple and strawberry jam) on blood sugar and insulin needs of the patients was studied in 40 patients with insulin-dependent diabetes. The results were compared with those, obtained with the consumption of similar fruit products, sweetened by industrial sugar. The study was performed by an apparatus for automatic regulation of blood sugar (artificial endocrine pancreas--Biostator), which supplies the organism of the patients, overloaded with the respective product, with insulin, depending on the degree of glycemia and guarantees "normal" utilization of the product. The results obtained reveal that the blood sugar is slightly increased with the dietetic products, the peak of the blood sugar curve is lower and less insulin is supplied automatically by the biostator during the loading with the product. All values are lower, with a statistical significance, for the dietetic products as compared with the non-dietetic ones (p less than 0.05 to 0.001). Those data provide grounds to recommend the products studied as proper to be included in the diet of the diabetic patients.

Blood Glucose↗
PubMed1982

[Diet with maximum restriction of caloric intake in diabetes mellitus and obesity].

To a group of 40 diabetic patients and obesity, a treatment was conducted by dietetic regimen of maximum restriction of the daily calories, from 3352 to 5028 kilojoules (800 to 1200 kilocal) according to obesity degree. Prior to treatment, only 10 per cent of the patients were with compensated diabetes. The treatment in 10 per cent of them was only a diet and in 5 per cent--insulin and in 85 per cent--peroral drugs. Completely compensated were 90 per cent of the patients subjected only to a diet, and in 10 per cent the inclusion of 5-10 mg maninil daily was necessitated. Body weight reduction with 3650 g was obtained within an average of 24 hospital days. All parameters of lipid metabolism, followed up at the beginning and at the end of the treatment were diminished: total fats (not significantly), cholesterol (significantly in females), triglycerides (significantly in males), betlipoproteins (significantly in females) and ketobodies (significantly for both sexes). In 20 patients with hyperlipoproteinuria, type IV, symptomatic anomaly in lipid metabolism was admitted, because after the treatment, only eight remained with such type of deviations. The dietetic regimen of maximum restriction of the calories applied by the authors, is admitted to be effective, with no risk of ketoacidosis, easy to apply and is recommended for the practice.

Blood Glucose↗
PubMed1978

[Pathogenesis of diabetes in adulthood. I. Insulin secretion at different evolutionary phases of diabetes].

Intravenous loading with glucose and glucose+tolbutamid was conduced in five groups of subjects, selected in a way that the intensity of insulin secretion gradually decreases from one group to the other (control group, relatives of patients with diabetes, diabetics sensitive to SUP and diabetics resistant to SUP). With insulin deficiency (in the last three groups) the early insulin secretion (absence of summit in IRI curve at the tenth minute), was established to grow weak, whereas in latent diabetes and in SUP sensitive diabetics it was preserved and insulinemia was protracted during the second half of the test. Early insulin secretion, in the control group and in the relatives of the diabetics, with loading with glucose-tolbutamid was twice as high as compared with that, obtained with loading solely with glucose. Diabetes at a mature age is concluded to be with a changed sensitivity of B-cells, at the beginning, versus glucose as a stimulator with signaling character, but the ability for synthesis and secretion of insulin, in general, is preserved. With the evolution of diabetes defect, the falling-off of insulin-synthesis ability is included in the pathogenetic mechanisms. A state of complete insulin deficiency develops--hence non-sensitivity to SUP.

Adult↗