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1.
In good agreement with earlier findings (1–8) legal abortion had been induced successfully with Csapo's method of “Prostaglandin Impact” (PGI) in 44 out of 50 sedated patients. They were 25±1.1 years of age, 11.3±0.2 weeks pregnant, para 1.1±0.2. Only a PGI (10 mg PG F2α) was delivered into the extraovular space. In 44 women, this single PGI provoked 40% progesterone (P)-withdrawal in 3 hours (P < 0.001) and 64% P-withdrawal (P < 0.001) in 15.3±0.9 hours, when the patients aborted. The remaining 6 women, whose P-withdrawal was only 14% at 3 hours without continuation during 24 hours, failed to abort. Thus in PG-induced abortions the regulatory significance of rapid and continued P-withdrawal (1–8) had been verified.The side effects were mild, transient and acceptable. The “Abortion Score” was 86. There were no serious complaints or complications during the study and followup. Since even in the 6 cases of failure the cervix dilated sufficiently to allow curettage (without surgical dilatation), the therapeutic benefits of the single PGI technique should be further examined in those services, where constant medical supervision (for determining the necessity and timing of repeated PGI) is not available.  相似文献   

2.
The fossil evidence of the “robust” australopithecines is reviewed with an emphasis on the taxonomic divisions and evolutionary relationships among this group of hominids. The hypodigms of A. robustus, A. crassidens and A. boisei are described, and the significance of morphological variation within and between these species is assessed. Phylogenetic relationships among the “robust” australopithecines are examined using maximum parsimony analysis, and evolutionary scenarios are evaluated in the light of recent discoveries in East Africa.  相似文献   

3.
4.
Functional architecture of the AChE active center appears to be characterized by both structural “rigidity”, necessary to stabilize the catalytic triad as well as by flexibility in accommodating the different, high affinity AChE ligands. These seemingly conflicting structural properties of the active center are demonstrated through combination of structural methods with kinetic studies of the enzyme and its mutant derivatives with plethora of structurally diverse ligands and in particular with series of stereoselective covalent and noncovalent AChE ligands. Thus, steric perturbation of the acyl pocket precipitates in a pronounced stereoselectivity toward methylphosphonates by disrupting the stabilizing environment of the catalytic histidine rather than through steric exclusion demonstrating the functional importance of the “rigid” environment of the catalytic machinery. The acyl pocket, the cation-binding subsite (Trp86) and the peripheral anionic subsite were also found to be directly involved in HuAChE stereoselectivity toward charged chiral phosphonates, operating through differential positioning of the ligand cationic moiety within the active center. Residue Trp86 is also a part of the “hydrophobic patch” which seems flexible enough to accommodate the structurally diverse ligands like tacrine, galanthamine and the two diastereomers of huperzine A. Also, we have recently discovered further aspects of the role of both the unique structure and the flexibility of the “hydrophobic patch” in determining the reactivity and stereoselectivity of HuAChE toward certain carbamates including analogs of physostigmine. In these cases the ligands are accommodated mostly through hydrophobic interactions and their stereoselectivity delineates precisely the steric limits of the pocket. Hence, the HuAChE stereoselectivity provides a sensitive tool in the in depth exploration of the functional architecture of the active center. These studies suggest that the combination of “rigidity” and flexibility within the HuAChE gorge are an essential element of its molecular design.  相似文献   

5.
From March through April 1998, a massive “red tide” occurred in coastal waters of south China, including Hong Kong. The “red tide” rapidly killed various species of caged fish and affected coral fishes, killing a few of them, and caused great economic loss and ecological damage. Samples collected from a permanent station located in Port Shelter revealed a new dinoflagellate species, Karenia digitata which was suspected to be the causative species of this “red tide”. Species composition and abundance analysis revealed that an algal bloom persisted in Port Shelter during this entire period. Diatoms and dinoflagellates were the two main groups which dominated the phytoplankton and, in general, when there was an increase in the density of diatoms there was a decline in the density of dinoflagellates, and vice versa. The suspected “red tide” causative species together with other dinoflagellate species started to bloom in late February and reached their highest density on 18 March, when fish kills were first reported at Crooked Island, a semi-enclosed bay to the northeast of Hong Kong. During a 16-week period, dinoflagellate species dominated three times, and coincided with low wind speeds. Constant salinity and a continuing increase in sea surface water temperature suggested warm water intrusion into Hong Kong’s coastal waters during this “red tide” bloom period. Various nutrient elements, e.g. NH4-N, total Kjeldahl nitrogen (TKN), and PO4-P were high at the beginning of the bloom but experienced a sharp decrease thereafter. It is suggested that this early 1998 massive “red tide” in Hong Kong waters might have been triggered by a synchronous appearance of optimal climatic, nutritional and hydrographic conditions.  相似文献   

6.
Occasional spontaneous “action potentiais” are found in mature hyphae of the fungus Neurospora crassa. They can arise either from low-level sinusoidal oscillations of the membrane potential or from a linear slow depolarization which accelerates into a rapid upstroke at a voltage 5–20 mV depolarized from the normal resting potential (near − 180 mV). The “action potentiais” are long-lasting, 1–2 min and at the peak reach a membrane potential near −40 mV. A 2− to 8−fold increase of membrane conductance accompanies the main depolarization, but a slight decrease of membrane conductance occurs during the slow depolarization. Two plausible mechanisms for the phenomenon are (a) periodic increases of membrane permeability to inorganic ions, particularly H+ or Cl- and (b) periodic decreases in activity of the major electrogenic pump (H+) of the Neurospora membrane, coupled with a nonlinear (inverse sigmoid) current-voltage relationship.Identification of action potential-like disturbances in fungi means that such behavior has now been found in all major biologic taxa which have been probed with suitable electrodes. As yet there is no obvious function for the events in fungi.  相似文献   

7.
The design of artificial hemoproteins that could lead to new biocatalysts for selective oxidation reactions of organic compounds presents a huge interest especially in pharmacology, both for a better understanding of the metabolic profile of drugs and for the synthesis of enantiomerically pure molecules that could be involved in the design of drugs.The present results show that the so-called “host-guest strategy” that involves the non-covalent incorporation of anionic water-soluble iron-porphyrins into xylanase A from Streptomyces lividans, a low cost protein, leads to such an artificial hemoprotein that is able to perform the stereoselective oxidation of sulfides.  相似文献   

8.
Over the past two decades there has been increasing interest in developing indicators to monitor environmental change. Remote sensing techniques have been primarily used to generate information on land use/land cover changes. The US Fish and Wildlife Service has used this technology to monitor wetland trends and recently developed a set of remotely-sensed indicators to characterize and assess trends in the integrity of natural habitat in watersheds. The indices largely focus on the extent of “natural” cover throughout a given watershed, with an emphasis on locations important to fish, wildlife, and water quality. Six indices address natural habitat extent and four deal with human-caused disturbance. A composite index of natural habitat integrity combining the habitat extent and habitat disturbance indices may be formulated to provide an overall numeric value for a watershed or subbasin. These indices facilitate comparison between watersheds (and subbasins) and assesssment of trends useful for environmental monitoring. This paper describes the indices and presents an example of their application for characterizing and assessing conditions of subbasins within Delaware’s Nanticoke River watershed.  相似文献   

9.
Bundles of microtubular structures appear in the cytoplasm of spermatids of the African frog Dicroglossus occipitalis. They are observed in the vicinity of axonemes. Natural tubulin polymerization leads to the formation of hooks on microtubular structures. They can be related to experimentally induced tubulin hooks. The direction of curvature of the hooks allows us to define the polarity of the bundles. This is opposite to the polarity of axonemal microtubules: Bundles and axonemes are antiparallel. Under colchicine action, arch-like microtubular structures are shown to open in the same direction as they lock. This enables us to characterize their opening and locking site: It corresponds to the place of the “11th filament” described in microtubular structures such axonemes. The “11th filament” is thus demonstrated to be the most susceptible to natural opening and to the action of colchicine in microtubular structures.  相似文献   

10.
A theory of transport via a “carrier” based on Wyman's theory on multiple equilibria is presented. By taking into account the detailed balance principle, it is possible to simplify the flux expressions and their coupling coefficients. In this way, Onsager's rules are derived. An experimental approach to the model is proposed.  相似文献   

11.
Watermass stratification has been considered the essential physical condition that dinoflagellates require to bloom because of their relative inability, unlike diatoms, to tolerate the elevated shear-stress associated with water-column mixing, turbulence and high velocity, coastal currents. The swimming speeds of 71 flagellate taxa, with a focus on dinoflagellates, are compared to the turbulence fields and vertical velocities that develop during representative wind conditions, upwelling and at frontal zones. The results suggest that the classical stratification–dinoflagellate bloom paradigm needs revision. Tolerance of turbulence, growth within well-mixed watermasses and survival and dispersal while entrained within current systems are well developed capacities among dinoflagellates. Their secretion of mucous, often copious during blooms, is suggested to be an environmental engineering strategy to dampen turbulence. Biophysical tolerance of turbulence by dinoflagellates is often accompanied by high swimming speeds. Motility speeds of many species exceed in situ vertical current velocities; this also allows diel migrational patterns and other motility-based behavior to persist. Species belonging to “mixing-drift” life-form assemblages can increase their swimming speeds through chain formation, which helps to compensate for the increased turbulence and vertical water-column velocities of their habitats. The ability of dinoflagellate species to tolerate the vertical velocities of offshore, frontal zones, where abundant populations often develop, suggests that fronts may serve as “pelagic seed banks”, occurring as pelagic analogues of nearshore seed beds, from which seed stock is dispersed. The different ecologies associated with the hypothesized, “pelagic seed banks” of vegetative cells and the “seed beds” of resting stage cells deposited onto sediments are discussed. There is a contradiction in the stratification–HAB paradigm: the quiescent conditions of a stratified watermass, with its characteristic nutrient-poor conditions are expected to promote stasis of the population, rather than growth and blooms. The analyses suggest that dinoflagellate blooms do not preponderate in stratified watermasses because the bloom species are biophysically intolerant of the higher velocities and turbulence of more mixed watermasses. The watermass stratification that often accompanies flagellate blooms is probably a secondary, parallel event and less essential than some other factor(s) in triggering the observed bloom.  相似文献   

12.
The mechanism of recognition by natural killer (NK) cells is still unknown. A dynamic model is formulated describing recognition or NK-sensitive target cells (TCs) by NK cells of NK-like cells. This model does not assume the presence of the specific NK-receptor(s) on the membrane of NK cells and corresponding specific ligands on the NK-sensitive TCs. We suggest: (1) the expression of various kinds of “non-NK receptors” and corresponding ligands (counter-receptors) on the plasma membrane of the same NK cell and, possibly, of TCs (e.g. LFA-1 and ICAM-1-ICAM3, CD2 and LFA-3; receptors for TNF and corresponding ligand etc.); (2) the presence of multiple disorders in the organization of “extracellular matrix-surface membrane-submembrane cytoskeleton” assembly of the NK-sensitive TCs; (3) non-specific primary linking of NK cell with TCs, which induces a transfer of vesicles or membrane fragments from the NK surface to the target cell surface (and perhaps vice versa). These processes may also permit the transfer of many types of receptor and counter-receptor molecules from the surface of one conjugated cell to another by vesicles or membrane fragments. After transferral through the intercellular cleft, the free receptors and counter-receptors will be localized on both cell surfaces at the contact region between conjugated cells. By this model the NK cell can “harpoon” the TC and enhance the binding forces between cells up to the critical level and then switch on killing mechanisms for the TC. By means of this “harpoon” model of cell recognition, it seems possible to explain the nature of the wide polymorphism of TCs which are sensitive to the effect of NK and NK-like cells. A mathematical model of the NK cell cytotoxic reaction is described. The model describes many nonlinear peculiarities of the cytotoxic process and predicts some new phenomena. We suggest new approaches of manipulation of cell membranes which can transform NK-resistant target cells in NK sensitive cells and vice versa.  相似文献   

13.
The PGE2-analogue Sulproton (16-phenoxy·ω-17,18,19,20-tetranor-PGE2-mythylsulfonylamide) was administered to 200 medically and gynecologically normal women who were 17±0.4 days beyond their expected menstrual period and who had a positive pregnancy test. The intramuscular impact dose (500 μg repeated after 4 hours) caused an immediate tonic uterine contraction which compromised the estradiol 17β, progesterone and chorionic gonadotropin production within the fetoplacental unit, and thereby allowed the evolution of cyclic uterine activity, cervical dilatation and tissue expulsion.Pregnancy termination was complete in 92% of women, 5.5% required surgical curettage and 2.5% were given a second Sulproston treatment 2–3 weeks after the first to remove retained tissue from the uterus. The medical induction of menstruation was preferred by 83% of the women who had previously experienced surgical termination of pregnancy. Normal menstruation resumed in all women after 36±0.9 days. The majority of 42 women questioned found Sulproston a satisfactory, safe, simple and effective drug regimen for “menstrual induction”.  相似文献   

14.
In 30 volunteers, 7 to 22 weeks pregnant, legal abortion had been induced successfully with the extraovular “Prostaglandin Impact” (PGI) (1). The patients were 24.8±1.1 years old (Means ± S.E.), para 1.6±0.3. At the 14.8±0.7 weeks of pregnancy and under sedation an initial dose of 10.0±0.0 mg PG F2α had been delivered transcervically into their extraovular (E.O.) space. This dose had been increased if accidental rupture of their fetal membranes resulted in intraamniotic (I.A.) treatment. The initial PGI of 16.0±2.0 mg was supplemented by additional PG doses, up to 27.0±2.9 mg, if clinical progress was slow. The patients responded to the initial PGI with sustained uterine contracture; rapid and continued progesterone (P) withdrawal, from 59.9±3.0 ng/ml to 30.7±2.1 ng/ml (49%); and with the progress of time high level cyclic intrauterine pressure (IUP). The 26% P-withdrawal, measured 3 hours after PGI was already significant (P < 0.001). Abortion was complete in 25 and incomplete in 4 patients, while 1 gravida had been curetted at 2 cm cervical dilatation. The instillation-abortion time (IAT) was short, only 13.0±1.1 hours. No side effects were observed in 17 patients, while 8 gravidas vomited (usually once) and 5 had transient increase in blood pressure. Extensive laboratory tests revealed no significant deviations from normality, during and after PG treatment. Blood transfusion was given to 2 patients (partly detached placentae and hemorrhage), antibiotics resolved 2 cases of endometritis and curettage removed (2 weeks after abortion) a small placental residue.The fetal membranes were accidentally ruptured in 11 patients and in these women the slow contracture response of the uterus signaled I.A. (rather than E.O.) PGI. The initial PG dose was increased, therefore, from 10.0±0.0 mg to 25.9±3.9 mg (P < 0.001) and the total dose from 20.0±2.0 to 42.3±4.8 mg (P < 0.001), to compensate for the lesser efficacious I.A. administration. In spite of this massive increase in the initial and total doses of PG, the rate and degree of P-withdrawal, the IAT, the incidence of side effects and the “Abortion Score” (AbS) of these 11 patients were similar to those of the 19 gravidas who received E.O. PGI. This finding, the good clinical outcome of the earlier (1) and the present study suggests that the transcervical E.O. PGI (regardless of accidental I.A. treatment) is a recommendable procedure for the non-surgical termination of pregnancy during the 1st half of gestation.  相似文献   

15.
Shifts between adaptive peaks, caused by sampling drift, are involved in both speciation and adaptation via Wright's “shifting balance.” We use techniques from statistical mechanics to calculate the rate of such transitions for a population in a single panmictic deme and for a population which is continuously distributed over one- and two-dimensional regions. This calculation applies in the limit where transitions are rare. Our results indicate that stochastic divergence is feasible despite free gene flow, provided that neighbourhood size is low enough. In two dimensions, the rate of transition depends primarily on neighbourhood size N and only weakly on selection pressure (≈sk exp(− cN)), where k is a number determined by the local population structure, in contrast with the exponential dependence on selection pressure in one dimension (≈exp(− cNs)) or in a single deme (≈exp(− cNs)). Our calculations agree with simulations of a single deme and a one-dimensional population.  相似文献   

16.
The COST Action 2103 “Advanced Voice Function Assessment” is a joint initiative of speech processing teams (engineers and physicists) and the European Laryngological Research Group (ELRG) (laryngologists/phoniatricians). The Action officially started in December 2006, and is running till the end of 2010. 17 European countries are involved. A main objective is a better understanding of the relationship between biomechanical changes at the level of the vocal folds – as induced by pathology and tissue reaction to strain – and alterations of the acoustical voice signal. This needs to result in developing accurate, objective and clinically useful methods of investigation of voice quality in patients, and of strategies for preventing occupational voice disorders in professional speakers. Modelling is an essential tool in this process.  相似文献   

17.
The synthesis of specific proteins at different stages in the development of mouse epidermis was investigated. The epidermis from mice of an age range from 16 days of fetal life to 7 weeks postpartum was prepared by maceration in acetic acid, and the total proteins were separated by SDS-polyacrylamide gel electrophoresis. The appearance of particular proteins at different developmental stages was correlated with the morphology of the epidermis at the same stage. Several qualitative and quantitative changes in the protein patterns were observed during development, the significance of which is discussed. A protein of molecular weight approximately 27,000 was the major component of a group of closely related proteins which appeared simultaneously with the production of mature keratohyalin granula in 18-day fetal mouse epidermis. Isolation and characterization of this protein showed it to be a “histidine-rich protein.” Its concentration in the epidermis decreased as the number of keratohyalin granula diminished with increasing age. The protein could be localized exclusively in the keratohyalin granula by a fluorescence method involving staining with dansyl chloride. This method was also used to detect “histidine-rich protein” on polyacrylamide gels.  相似文献   

18.
Different authors working in the Mediterranean area have reported a distinctive change in the assemblages of keeled globorotaliids coinciding with the FAD ofGloborotalia conomiozea Kennett. This change which has now been observed in the Guadalquivir basin consists of the abrupt disappearance of the “Globorotalia menardii” group, which is then replaced by theGloborotalia miotumida group.This event has been found in a number of areas of the Atlantic Ocean and it is proposed that it can be used to recognize the Tortonian-Messinian boundary in this realm whereG. conomiozea occurs only sporadically.  相似文献   

19.
The universe of cellular forms has received scarce attention by mainstream neo-Darwinian views. The possibility that a fundamental trait of biological order may consist upon, or be guided by, developmental processes not completely amenable to natural selection was more akin to previous epochs of biological thought, i.e. the “bauplan” discussion. Thirty years ago, however, Lynn and Tucker studied the biological mechanisms responsible for defining organelles position inside cells. The fact that differentiated structures performing a specific function within the eukaryotic cell (i.e. mitochondrion, vacuole, or chloroplast) were occupying specific positions in the protoplasm was the observational and experimental support of the ‘morphogenetic field’ notion at the cellular level. In the present paper we study the morphogenetic field evolution yielding from an initial population of undifferentiated cells to diversified unicellular organisms as well as specialized eukaryotic cell types. The cells are represented as Julia sets and Pickover biomorphs, simulating the effect of Darwinian natural selection with a simple genetic algorithm. The morphogenetic field “defines” the locations where cells are differentiated or sub-cellular components (or organelles) become organized. It may be realized by different possibilities, one of them by diffusing chemicals along the Turing model. We found that Pickover cells show a higher diversity of size and form than those populations evolved as Julia sets. Another novelty is the way that cellular organelles and cell nucleus fill in the cell, always in dependence on the previous cell definition as Julia set or Pickover biomorph. Our findings support the existence of specific attractors representing the functional and stable form of a differentiated cell—genuine cellular bauplans. The configuration of the morphogenetic field is “attracted” towards one or another attractor depending on the environmental influences as modeled by a particular fitness function. The model promotes the classical discussions of D’Arcy Thompson and the more recent views of Waddington, Goodwin and others that consider organisms as dynamical systems that evolve through a ‘master plan’ of transformations, amenable to natural selection. Intriguingly, the model also connects with current developments on mechanobiology, highlighting the informational–developmental role that cytoskeletons may play.  相似文献   

20.
“Bryndza” is a traditional Slovak dairy product (type of soft cheese) made from sheep cheese which was ripened for 14 days. Because its manufacture, transporting and/or storing represent conditions which facilitate contamination, the effect of enterocin CCM4231 in “bryndza” was investigated with the aim to reduce the contaminant agents. “Bryndza” was divided into equal portions (50 g). The experimental sample (ES) as well as the control sample one (C1) were inoculated with Listeria innocua Li1 strain. The other control samples C2 and C3 were without Li1 strain. C3 control was selected as a reference control. ES and C2 portions were treated with purified enterocin CCM4231 in a concentration of 6400 AU/ml. Before the experimental inoculation, “bryndza” was checked for the presence of contaminant agents. The experiment lasted 1 week and the samples were stored in the refrigerator at 4 °C. Sampling was performed on day 1, on day 4 and on day 7. The control samples C2 and C3 were checked only on day 1 and then after 1 week. The following contaminant agents were detected in “bryndza” before its experimental inoculation with L. innocua Li1 strain: Escherichia coli in the amount 103 cfu/ml/g, Staphylococcus aureus (102 cfu/ml/g) and enterococci (104 cfu/ml/g). In the control sample C2, the number of E. coli was reduced to 102 cfu/ml/g. Enterococci and staphylococci were totally eliminated there. Concerning C3 control, natural decrease of bacteria was found and/or their unchanged counts. The value of pH (5) was stable during the whole experiment. In the experimental sample inoculated with Li1 strain, its counts were decreased immediately after enterocin CCM4231 addition approximately by one order of magnitude. This inhibitory effect was also detectable on day 4 by the difference of one order of magnitude between ES and C1. On day 7, 103 cfu/ml/g of Li1 strain were detected in both samples (ES, C1). The difference by one order of magnitude indicated, an inhibitory effect of enterocin CCM4231 in “bryndza”. However, bacteriocin activity was not determined by laboratory analyses.  相似文献   

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