Frequency of the stages in the cycle of the seminiferous epithelium in the rat

This study determined the optimum number of tubules to be counted per testis cross section, and the number of animals per treatment group, when changes in stage frequencies in the cycle of the seminiferous epithelium are criteria for assessing effects of treatment on spermatogenesis. A data base of 9,672 observed and staged tubules was collected from testicular cross sections of 15 Sprague-Dawley rats. A significant variation between animals was found for the frequencies of Stages I, II, IV, VI, VIII, and XIII. Computer simulation was used to randomly select different combinations of animal and tubule numbers from the observed data. Stage frequency means from each simulation experiment were compared statistically to observed mean frequencies. A model that used data from all 14 stages was analyzed. The following conclusions were made: a) a minimum of 200 tubule cross sections/testis is recommended for estimating stage frequencies; b) for a fixed number of tubules scored, the number of animals sampled is more important than the number of tubules per animal in reducing variance; c) to detect a difference of 2 standard deviations from the mean with a 2% error rate and examining 200 tubules/testis, at least 12 animals must be used per group when assessing all 14 stages; d) when individual stages are examined using 10 animals per group, only Stage VII has 80% or greater power of test (alpha = 0.05) to detect a frequency difference; e) pooling stages into 3-4 groups is recommended to improve the power of detecting a treatment difference.     

Selenocysteyl-tRNA occurs in the diatom Thalassiosira and in the ciliate Tetrahymena

Selenocysteyl-tRNAs that decode UGA were identified previously in animal and bacterial cells and the genes for these tRNAs have been shown to be widespread in animals and eubacteria. In the present study, we identify a selenocysteyl-tRNA that codes for UGA in Thalassiosira pseudonana, which is a diatom, and in Tetrahymena borealis, which is a ciliate. The fact that these very diverse unicellular organisms also contain a selenocysteyl-tRNA suggests that selenocysteine-containing proteins and the use of UGA as a codon for selenocysteine are widespread, if not ubiquitous, in nature.     

Persistence in the chemostat

Sufficient conditions are obtained for persistence in chemostat models for interactions of a limiting nutrient (or substrate) and two populations, and for two limiting complementary substrates and a single population. The results of Freedman and Waltman are extended for the three interacting predator-prey populations.     

Self-organization in the determination of the size of the axial structures in the embryogenesis of the clawed toad

Experiments were performed using X. laevis embryos during gastrulation and neurulation (stages 10, 11 1/2, 12 1/2, 13 1/2, 15 and 18). Part of presumptive epidermis and lateral plate mesoderm was removed, and embryos raised until stage 25. The size of axial structures (notochord, somite mesoderm, central nervous system) was determined using serial histological sections and compared with that of control embryos. In experimental embryos, the size of axial structures was decreased. Until a specific stage of development, close correlation was found between the volume of embryonic compartment corresponding to a particular, structure and the volume of presumptive epidermis and lateral plate mesoderm. This stage is individual for each axial organ: middle gastrula (stage 11 1/2) for notochord, late gastrula (stage 12 1/2) for somite mesoderm, and late neurula (stage 18) for central nervous system. This data suggest that differentiation pattern of ecto-mesodermal rudiment is subject to regulation during gastrulation-neurulation, and subdivision of ectoderm and mesoderm into axial and non-axial tissues is a self-organizing process.     

Prospects of trawl fishing in the littoral zone of the Peter the Great Bay in the autumn period

The results of experimental trawl fishing in the littoral zone of the Amur Bay are summarized. Using a motor boat and a launch for trawling with experimental trawl during the research works made it possible to obtain new data on the species composition, distribution, and stock density of the fishes in the littoral zone of Peter the Great Bay. Light trawl is promising not only for research purposes but also for seasonal fishing.     

Maximum in the stability of the amorphous state in the system water--glycerol--ethanol.

When the proportions of glycerol and ethanol vary for a given water concentration, the stability of the amorphous state of the whole solution in the system water-glycerol-ethanol passes through a maximum. This ternary system may then be much more interesting for cryoprotection than the system water-glycerol-DMSO. The phase transitions on rewarming at several rates after rapid or slow cooling, or after annealing, were observed by calorimetry and the various states between the transitions including the amorphous state were observed by X-ray diffraction. However, this system is much more complicated than the system water-glycerol-DMSO, due to the existence of two ethanol hydrates. Since, beyond a certain ethanol concentration, a first melting occurs before the devitrification, the stability of the amorphous state could no longer be defined by the critical warming rate. It was then defined by the amount of crystals formed on cooling, which was surprisingly reproducible in the present experiments for each cooling rate. The maximum in the stability occurs for rather low ethanol concentrations, which is of interest since ethanol is more toxic that glycerol. The concentration corresponding to the maximum depends on the cooling rate. It occurs at about 20% ($\text{w}\text{w}$) ethanol/(glycerol + ethanol) for the 50 and 55% ($\text{w}\text{w}$) water solutions. It is shifted to 40% ($\text{w}\text{w}$) ethanol/(glycerol + ethanol) for the 60% ($\text{w}\text{w}$) water solutions.     

2-Hydroxylation of estrogens in the brain participates in the initiation of the preovulatory LH surge in the rat

Estradiol-2-hydroxylase, the enzyme responsible for the conversion of estrogens to catechol estrogens was measured in the brain of female rats at specific stages of the estrus cycle. Radiometric measurements of the enzyme activity in microsomal, mitochondrial, and synaptosomal fractions of the brain revealed a sharp increased in activity at proestrus just prior to the preovulatory LH surge. The enzyme activity declined to lower levels at diestrus and metestrus. No comparable fluctuations were noted in the liver enzyme. These changes in brain enzyme activity in conjunction with demonstrated positive feedback of exogenous catechol estrogens on pituitary LH release, suggest that a rise in endogenous catechol estrogen formation in the brain may be responsible for the physiological induction of the preovulatory LH surge.     

Endopeptidase-24.11 in the adenohypophysis of the pig is localized in the gonadotrophic cells

Endopeptidase-24.11, an ectoenzyme with a key role in metabolizing peptides at cell surfaces, is present in the adenohypophysis. A specific polyclonal antibody to the endopeptidase has been used to explore its localization in cryostat sections of pig pituitary glands by an immunoperoxidase method. Immunoreactivity was symmetrically but not uniformly distributed over the anterior lobe, with the highest intensity a zone just beneath the capsule along the anterior surface. In detail, the staining was observed to be in the cell membrane, but in some cells a small area of intense paranuclear staining was also observed. Serial 5 micron sections were immunostained alternately for endopeptidase-24.11 and for pituitary proteohormone. Luteinizing hormone (LH), follicular stimulating hormone (FSH), thyrotropin, adrenocorticotropin, prolactin and growth hormone were studied in this way. It was possible to identify groups of cells in adjacent sections and a good correlation was observed for endopeptidase-24.11-immunoreactivity with that for LH and FSH. The association of the endopeptidase with gonadotrophs was confirmed by double labelling. No evidence of colocalization was observed with the other proteohormone antibodies. We conclude that among the cells of the adenohypophysis only the gonadotrophs express endopeptidase-24.11 and discuss the possible significance of this observation in regard to the termination of peptide signals, such as that of luteinizing hormone-releasing hormone (LHRH) acting at this site.     

Intracisternal granules in the somatotrophs in the anterior pituitary of the mouse

A detailed study of the anterior pituitaries of pregnant and lactating mice revealed changes occurring in the ultrastructure of the somatotrophs. The rough endoplasmic reticulum cisternae become greatly dilated forming channels that are continuous with the perivascular space. This occurrence expands the membrane surface available for the release of hormone. Individual granules and cytoplasmic islands containing numerous granules appear in these channels. This suggests an alternative mechanism for granule release which would facilitate a rapid response to increased hormone requirement.     

A photographic representation of the variability in the G-banded structure of the chromosomes in the mouse karyotype

Analysis of the mouse chromosomes is becoming increasingly important in many fields of genetic research. It is generally considered that the mouse chromosomes are more difficult to analyse than, for example, human chromosomes which has often led to their misidentification. This article presents a guide to the correct identification of trypsin-Giemsa banded chromosomes from the mouse. The variability in the G-banded structure of each chromosome is presented pictorially together with some suggestions for their unequivocal identification. Since many of the mouse chromosomes have similar banding patterns, those chromosomes which are more frequently misidentified have been compared and contrasted. Finally a summary of the main features for the identification of each chromosome is presented.     

Genetic variation in the timing of reproduction in the Great Tit

Summary About 40% of the population variation in the initiation dates of first clutches within years is genetically determined. The onset of laying, which is determined by the female, is not detectably influenced by spatial heterogeneity of the study area.There is a variable selection favoring early, middle, or late laying in some years. Over the study period as a whole there is a slight net selection for laying relatively late.The implications for a potential rapid evolutionary change are discussed. The conclusion is reached that the population mean might change with rates of up to one week per five generations, which is approximately a decade.     

Predicted microbial biomass in the rhizosphere of barley in the field

Summary Laboratory data for the loss of root material by barley and field data for the growth of barley plants in Syria and in England have been combined to predict the amount of material lost by barley roots during a season, and to predict the resulting microbial biomass in the rhizosphere. The predicted microbial biomass C in the rhizosphere ranged from 10–34% of the total plant biomass C depending mainly upon the value used for rate of loss of root material. Total loss of root material predicted during a season in England constituted 7.7–25.4 percent of C fixed by photosynthesis. The major assumptions made in these calculations are considered, and the predicted values discussed in relation to reported values for soil microbial biomass, CO₂ fluxes from soil and associative nitrogen fixation.     

Dendroclimatic signals in the pine and spruce chronologies in the Solovetsky Archipelago

Searching for a robust tree-ring parameter useful for paleoclimatic purposes is one of the most demanding topics in the modern paleoscience. Since Blue Intensity has already expressed itself in different geographical locations all over the world as a possible replacement for maximum density, close attention is paid to investigate features of the inferred signal. The Solovki Islands is a unique location in Northern Russia where two important factors that make this territory attractive for developing a long tree-ring chronology have been met: modern long-living trees and building activities using old trees that were started by monks in the middle of the 16th century. The main goal of the research is to develop pine and spruce chronologies based on tree-ring width (TRW) and delta Blue Intensity (dBI) and to assess the ability of these parameters to be used as climate predictors. As a result, 14 conifer chronologies from 7 sites (4 for pine and 3 for spruce) were developed. The composite pine and spruce chronologies span a period of 474 and 378 years each. Cross-correlation of dBI-based chronologies of both conifers is high (r = up to 0.71 while for TRW-based chronologies it is lower on average (−0.18 to 0.63). Intra-species correlation of TRW chronologies in some cases achieved even negative values (r = −0.18. Discrepancies found between TRW chronologies of pine and spruce could be explained by differences in climatic signals. Response function analysis with monthly temperatures revealed that growth of pine depends on the previous August, while spruce has a temporally stable and strong relation to June temperatures. Compared to TRW, dBI-based chronologies have a high correlation with summer temperatures (r = 0.64 and 0.66 for spruce and pine, respectively). Presented research points out the importance of the response function analysis suggesting that depending on goals of the study several tree-ring parameters could be used, e.g., tree-ring width of spruce responses to June temperatures, while dBI to the whole summer.     

On the role of the pineal in thermoregulation in the pigeon

Diurnal rhythm in body temperature of pigeons subjected to different experimental conditions (pinealectomized, sham-operated, melatonin-implanted, cold-exposed) was studied under a 12 h light and 12 h dark regimen. The body temperature of pigeons during photophase was higher than that during scotophase in the normal as well as every treatment group studied. Pinealectomized pigeons showed higher body temperature in the photophase as well as scotophase, than that of the normal and sham-operated birds when examined 2 or 3 weeks following the post-surgical acclimatization to 25 or 3 degrees C. However, subcutaneous implantation of melatonin pellets into pinealectomized pigeons nullified or even reversed the hyperthermic effect of pinealectomy. Exposure of pigeons to--18 degrees C for 280 min during photophase as well as scotophase, produced a marked drop in body temperature in pinealectomized, sham-operated and normal pigeons. The pinealectomized pigeons exhibited a higher body temperature than that of the sham-operated and normal ones when exposed to--18 degrees C during the photophase, but not during the scotophase. It was concluded that while the pineal is not necessary for maintaining the daily thermal rhythm in the avian body, it has a thermoregulatory role, in that it prevents rise in body temperature in warm (25 degrees C) acclimatized and chronic cold (3 degrees C) exposed birds. In acute short-term cold (--18 degrees C) exposure however, the temperature regulatory role of the pineal was not effective during the scotophase.     

The Pivotal Role of Astrocytes in the Metabolism of Iron in the Brain

Iron is essential for the normal functioning of cells but since it is also capable of generating toxic reactive oxygen species, the metabolism of iron is tightly regulated. The present article advances the view that astrocytes are largely responsible for distributing iron in the brain. Capillary endothelial cells are separated from the neuropil by the endfeet of astrocytes, so astrocytes are ideally positioned to regulate the transport of iron to other brain cells and to protect them if iron breaches the blood-brain barrier. Astrocytes do not appear to have a high metabolic requirement for iron yet they possess transporters for transferrin, haemin and non-transferrin-bound iron. They store iron efficiently in ferritin and can export iron by a mechanism that involves ferroportin and ceruloplasmin. Since astrocytes are a common site of abnormal iron accumulation in ageing and neurodegenerative disorders, they may represent a new therapeutic target for the treatment of iron-mediated oxidative stress.     

Cholesterol uptake in the small intestine of the rat in experiments in vitro

The kinetic and thermodynamic parameters of cholesterol uptake in the small intestine of rats were determined in vitro under normal and hypercholesterolemic conditions. It is established that the cholesterol uptake by the small intestine mucosa is a process of the zero order and the rate of its uptake is constant during the whole period of studies. The cholesterol uptake by mucosa during hypercholesterolemia occurs at a higher rate than under normal conditions. Activation energy for the cholesterol uptake is 10.52 Cal/mol under normal conditions, while it is reduced to 7.9 Cal/mol under experimental hypercholesterolemia. The experimental data permit suggesting that the membrane of the mucous brush border possesses a rather high energy barrier for the cholesterol uptake indicating the active nature of its uptake in the small intestine.     

Signalling Asymmetry in the Communication of the Water Strider Aquarius remigis in the Context of Dominance and Spacing in the Non-mating Season

The role of high-frequency ripple signals (HF signals) made by males of the water strider Aquarius remigis was studied in the contexts of competition for food and general spacing behaviour during the non-mating season. HF signals were played back through the ripple-producing legs of males during dyadic agonisdc encounters, using a signal-driven wire coil to oscillate a magnet glued to a leg. These signals were in addition to normal signals. The additional signals significantly increased the number of retreats by non-magneted males, showing that the signals increased the dominance of a non-territorial male. Hence, our results increase the number of contexts in which HF signals of A. remigis function. Males, but not females, avoided a site occupied by a magneted dead male through which HF signals were played. Thus, the communication system used by A. remigis males during competition for food seemed to be ignored by females, suggesting sex-specific signals even in a non-mating context. Evolutionary models of signalling often assume that contestants have evolved the same repertoire of signals in order to resolve conflicts peacefully. This water strider system thus poses an interesting challenge for future theoretical and empirical research on communication asymmetry.     

Thalassaemia in the British

Different forms of thalassaemia or related disorders were found in 116 people of apparently pure British stock. Among them were one family with a child homozygous for β-thalassaemia and eight heterozygous relatives, 16 families with 83 persons heterozygous for β-thalassaemia, two families with three persons with Hb H disease and three heterozygous for α-thalassaemia 1, one family with a child apparently homozygous for the “silent β-thalassaemia gene,” one family with six members heterozygous for a form of β-thalassaemia intermedia, and three families with 11 members heterozygous for different types of hereditary persistence of fetal haemoglobin. The clinical, haematological, and haemoglobin biosynthetic findings in these persons were similar to those of patients with thalassaemia from other racial groups. The heterozygous state for β-thalassaemia is overlooked in British patients, particularly during pregnancy, because it is not considered in the differential diagnosis of refractory anaemia. In many cases this leads to much unnecessary investigation and potentially harmful treatment.There seem to be several varieties of hereditary persistence of fetal haemoglobin production among British people. These conditions, while not causing anaemia, may cause difficulties during examination of maternal blood for fetal cells and may, if inherited with a β-thalassaemia gene, produce an unusually high level of Hb F in a person heterozygous for β-thalassaemia.     

Uncertainty in the tail of the variant Creutzfeldt-Jakob disease epidemic in the UK

Despite low case numbers the variant Creutzfeldt-Jakob disease epidemic poses many challenges for public health planning due to remaining uncertainties in disease biology and transmission routes. We develop a stochastic model for variant CJD transmission, taking into account the known transmission routes (food and red-cell transfusion) to assess the remaining uncertainty in the epidemic. We use Bayesian methods to obtain scenarios consistent with current data. Our results show a potentially long but uncertain tail in the epidemic, with a peak annual incidence of around 11 cases, but the 95% credibility interval between 1 and 65 cases. These cases are predicted to be due to past food-borne transmissions occurring in previously mostly unaffected genotypes and to transmissions via blood transfusion in all genotypes. However, we also show that the latter are unlikely to be identifiable as transfusion-associated cases by case-linking. Regardless of the numbers of future cases, even in the absence of any further control measures, we do not find any self-sustaining epidemics.     

Exploring the sequence patterns in the alpha-helices of proteins

This paper reports an extensive sequence analysis of the alpha-helices of proteins. alpha-Helices were extracted from the Protein Data Bank (PDB) and were divided into groups according to their sizes. It was found that some amino acids had differential propensity values for adopting helical conformation in short, medium and long alpha-helices. Pro and Trp had a significantly higher propensity for helical conformation in short helices than in medium and long helices. Trp was the strongest helix conformer in short helices. Sequence patterns favoring helical conformation were derived from a neighbor-dependent sequence analysis of proteins, which calculated the effect of neighboring amino acid type on the propensity of residues for adopting a particular secondary structure in proteins. This method produced an enhanced statistical significance scale that allowed us to explore the positional preference of amino acids for alpha-helical conformations. It was shown that the amino acid pair preference for alpha-helix had a unique pattern and this pattern was not always predictable by assuming proportional contributions from the individual propensity values of the amino acids. Our analysis also yielded a series of amino acid dyads that showed preference for alpha-helix conformation. The data presented in this study, along with our previous study on loop sequences of proteins, should prove useful for developing potential 'codes' for recognizing sequence patterns that are favorable for specific secondary structural elements in proteins.