Early development of the granule cell in the cerebellum of the chick embryo

The sequence of differentiation of the cerebellar granule cell in chick embryos from the eighth to the 15th days of incubation has been studied in Golgi-stained celloidin sections. In the germinal-cell phase, the presumptive granule cell sends out one or two horizontal processes which may originate either in the body of the cell or in the extension which attaches it to the pial surface. Thus the germinal cell may be converted into either a monopolar or a bipolar presumptive granular cell. Bipolar cells may have two processes of the same length (symmetrical cells) or of unequal length (asymmetrical cells). In the symmetrical as well as asymmetrical bipolar cells the leading process is formed, by means of which the perikaryon emigrates until it situates itself definitely in the internal granular layer. Thus, symmetrical and asymmetrical bipolar cells give rise to a granule cell with parallel fibers of equal or different lengths. The monopolar element may originate a second process or may remain in the monopolar phase until it reaches the internal granular layer. Once there, it completes the formation of the parallel fibers.     

Ultrastructure of the secretory cells of the submucosal glands in the human maxillary sinus

Tissue samples obtained from the lateral wall of the maxillary sinuses of five patients were examined by light microscopical, histochemical, and ultrastructural techniques. Submucosal glands were tubulo-alveolar mixed glands. The acini consisted of either all serous or all mucous cells, or a mixture of both. Serous granules were stained by toluidine blue, or by hematoxylin and eosin (H and E), but showed little or no reaction with periodic acid-Schiff (PAS) or Alcian blue. Mucous granules were pale in toluidine blue or H and E preparations, and consisted primarily of acid mucosubstances, as demonstrated by their staining reaction with PAS and Alcian blue. At the electron microscope level, the serous granules were either homogeneously dense, or showed a substructure consisting of at least two layers of distinctly different electron-opacity. Typical mucous droplets consisted of a fibrillar network dispersed in a translucent matrix. A second secretory product was present in the mucous cells in the form of elongated, membrane-bounded structures containing numerous parallel filaments, which measured about 55 Å in diameter. The mucous droplets and the filamentous bodies appear to arise from the opposite faces of the Golgi complex in the mucous cells. The filamentous bodies showed a pronounced tendency to fuse with the mucous droplets. All acini were surrounded by a well-defined myoepithelial layer and contained intercellular nerve terminals.     

Ecological significance of the dilation of the distal portion of the uterus of some trematodes]

Many trematodes parasitic in the oral cavity, pharynx or oesophagus of snakes and birds or in the cloaca of birds possess a sac-shaped dilation of the uterine distal portion or the organ itself is sac-shaped. Trematodes possessing such uterus lay periodically more or less portions of eggs. The time of egg laying depends on the frequency of some functions of the host's organs (food capture by the host, swallowing the food, defecation), which the trematodes inhabit.     

Development of the mammalian gonad: the fate of the supporting cell lineage

Sex determination in mammals is mediated via the supporting cell lineage in the fetal gonad. In the very early stages of gonadal development, the fate of the supporting cell population is critically dependent on the expression of the male-determining gene on the Y chromosome. If this gene is absent or fails to be expressed, or is expressed too late or in too small a number of supporting cells, all supporting cells (XX or XY) differentiate as pre-follicle cells and development proceeds along the female pathway. Supporting cells in which the male-determining gene is expressed in a timely manner differentiate as pre-Sertoli cells; given sufficient such cells, testis cords form and development proceeds in a male direction. If XX supporting cells are also present, a few may be recruited into the pre-Sertoli population and participate in testis cord formation. The subsequent fate of pre-follicle cells depends critically on interaction with the germ cell population in the developing gonad: absence of germ cells may lead to partial masculinization of the gonad, and/or to disappearance of the supporting cell component.     

Beyond the Four Corners of the Convention: Expanding the Scope of Jurisdiction of Law of the Sea Tribunals

In several recent Awards, Part XV tribunals constituted under the UN Convention on the Law of the Sea have been called upon to decide claims based on rights and obligations that find their source in a treaty, agreement, or otherwise binding instrument other than the Convention itself, or on customary international law. This article considers the extent to which such claims fall properly within the jurisdiction of a Part XV tribunal, either on the basis of the applicable law provision in Article 293(1) of the Convention, or on the basis of provisions of the Convention that make reference to other relevant rights and obligations.     

Effects of disturbances of acid-base equilibrium on the activity of the rumen

The effect on ruminal motility of NH4- or Na-acetate and Na- or K-lactate of various pH and doses infused into the jugular vein (i.v.) or carotid artery (i.a.) was studied in sheep with ruminal fistula I.v. infusion of NH4-acetate whenever it was accompanied by a considerable increase of the blood NH4 level potently inhibited the amplitude and frequency of ruminal contractions. I. a. administration produced more rapid and more apparent responses and a slightly elevated venous ammonia concentration than did the i.v. infusion. Thus the augmented blood ammonia level not only affected the smooth muscles and peripheral nerve endings but also inhibited the vegetative centres of the central nervous system. Infusion of Na-acetate and Na- or K-lactate solutions induced compensated acidosis or alkalosis which reduced the amplitude of ruminal contractions and produced respiratory disturbances. The latter were more apparent in alkalosis. In uncompensated acidosis or alkalosis, ruminal motility was permanently inhibited or abolished. The results appear to show that in not properly fed ruminants the frequently observed and long lasting compensated acidosis or alkalosis might influence the activity of the vegetative centres thus further metabolic disturbances and impaired gastrointestinal activity might follow the shifts in acid-base equilibrium.     

Presence of a nucleus or nucleus-deriving factors is indispensable for the formation of the spindle, the diastema and the cleavage furrow in the blastomere of the Xenopus embryo

The present study examines the indispensability of a nucleus or nucleus-deriving factors in the induction of cleavage in Xenopus eggs by testing cleavage in Xenopus eggs fertilized with ultraviolet (UV)-damaged sperm and deprived of the female nucleus. These eggs, which contain only one UV-damaged nucleus with one set of centrioles, undergo unique cleavages. Cleavage takes place in only one of the two blastomeres formed by the immediately preceding cleavage. Histologically, only one nucleus, which does not appear to be organized into typical chromosomes, is found in one of the two blastomeres formed by the immediately preceding cleavage. The typical bipolar spindle and the diastema, or a slit of astral rays, are formed in the blastomere that contains the nucleus. By contrast, only asters lacking the spindle and the diastema are formed in the remaining blastomeres, which do not contain a nucleus. The same results are obtained in eggs that contain two UV-damaged nuclei with one set of centrioles. In these eggs, cleavage appears to occur in one or two blastomeres that contain either or both of the nuclei and one bipolar spindle. In eggs that contain one intact and one UV-damaged nuclei, cleavage takes place quite normally with each blastomere containing one nucleus or one set of chromosomes as well as one bipolar spindle. Thus, there is a very close correlation between the presence of a nucleus and the formation of the mitotic spindle, the diastema and the cleavage furrow in the blastomeres of Xenopus embryos. We conclude that the presence of a nucleus or nucleus-deriving factors is indispensable for the formation of the bipolar spindle, the diastema and the cleavage furrow in the blastomeres of the Xenopus embryos.     

An ultrastructural evaluation of the reaction of the host cell membrane to the invasive phase of Candida albicans.

Ultrastructural studies of the invasive form of Candida albicans in patients with acute or chronic candidosis have demonstrated either (a) a close seal between the host cell membrane and the fungal cell wall or (b) a ruptured or damaged host cell membrane at the point of invasion. This was observed in samples from either oral or vaginal candidosis as the pathogen successfully enters the adjoining host cell. The variations appear to be related to the degree of resistance of the host cell membrane to the invading pathogen. This view is discussed.     

Value of the history in the office diagnosis of breast cancer.

A review of the histories of 1059 patients with breast problems seen consecutively in office consultation revealed an incidence of breast cancer of 13%. Patients over 50 years of age or whose mother or sister had had breast cancer had a substantially greater likelihood of having breast cancer. The finding of the problem on routine examination, a family history of breast cancer in a relative other than the mother or a sister, or prominent breast pain or nipple discharge made the diagnosis of cancer less likely. Menstrual status, a history of previous benign disease, nulliparity, current hormone therapy and duration of symptoms did not help identify the patient likely to have breast cancer. Much time could be saved for both doctor and patient in taking the history from patients with breast disorders. Only the patient''s age and the history of the mother and sisters with regard to breast cancer will help identify the "high-risk" patient. Other historical findings are either valueless or should be used to reassure these usually anxious women.     

Mechanical control of the time-course of contraction of the frog heart

Changes in load during most phases of an isotonic contraction of the frog and turtle heart increased or decreased the duration of the twitch. It was abbreviated by a maintained increase or by a brief decrease in load. The relaxing effect of these procedures developed with a delay lasting more than a second under some conditions and will be called lengthening deactivation. The reverse procedures, a maintained diminution or a brief increase in load, increased the duration of the twitch. This effect will be called shortening activation. Although the termination of relaxation may be delayed or advanced by the mechanical interventions mentioned, the normal time- course of isotonic relaxation was always resumed later, regardless of the starting level of the load, making it possible to measure accurately changes in the duration of the twitch. The responses to changes in load produce positive feedback during the isotonic contraction and explain, at least in part, the difference in the time- course of isotonic and isometric contraction. The effects of changes in load were much smaller and briefer in the atrium than the ventricle.     

Assessment of the Effect of Oil on the Potyvirus Aphid Transmission Process

Mineral oil sprays applied to plants or to artificial membranes were assessed for their effect on virus and helper component (HC), both of which are required for aphid transmission. Probing oil-treated surfaces prior to or after probing a virus-HC mixture, HC, or virus, reduced or abolished transmission. Oil also inhibited transmission when contacted after aphids had penetrated membranes which contained a virus + HC mixture. Oil had no apparent effect on aphid probing behaviour. The data support the hypothesis that oil affects the interaction of virus and HC with aphid mouthparts or alimentary tract.     

A proposal for the representation of the stereochemistry of quadrivalent centers

The broken wedge, broken line, solid bar, and broken bar are either not reasonable or can be replaced by only one type of solid wedge in the stereochemical formulation. A convention based on a one-wedge symbolization is proposed, where a or b is used instead of c, d, e, f, g , or h . © 1992 Wiley-Liss, Inc.     

Cryopreservation of the sperm of the Japanese bitterling

Sperm of the Japanese bitterling Tanakia limbata that had been cryopreserved with 5 or 10% methanol plus 95 or 90% foetal bovine serum (FBS) showed higher percentage and longer duration of motility than those that had been cryopreserved with 90% FBS and 10% DMSO, glycerol, N,N-dimethylacetamide or N, N-dimethylformamide. Foetal bovine serum, used as extender, had some cryoprotective effects when spermatozoa were cooled either with 10% methanol or without methanol. Spermatozoa, cooled to −40° C and then immersed in liquid nitrogen, had greater post-thaw motility than those cooled to −20, −60, or −80° C. The post-thaw percentage of motile spermatozoa increased significantly ( P < 0·001) with decreases in the freezing rate from 60 to 5°C min⁻¹. These results indicate that 10% methanol plus 90% foetal bovine serum is a suitable diluent for cryopreservation of bitterling spermatozoa and that samples should be cooled to -40°C at a low freezing rate for effective storage.     

Regulation of protein phosphorylation of the intermediate-sized filament vimentin in the ciliary epithelium of the mammalian eye

The intermediate-sized filaments of vimentin-type (Mr = 57,000) have been identified biochemically and immunochemically as a major cytoskeleton component in the ciliary epithelium of the mammalian eye. When human or rabbit ciliary processes, or cultured ciliary epithelial-derived cells were incubated in serum-free medium containing [32P]orthophosphate and any of the following agents: 1) beta-adrenergic agonists (isoproterenol or epinephrine), 2) direct activators of adenylate cyclase (cholera toxin or forskolin), 3) analogs of cyclic AMP (8-Br-cAMP), or 4) prostaglandin E1, the phosphorylation of vimentin was significantly enhanced. The maximal enhancement ranged, in vivo and in vitro, from about 3-fold in human to 5-fold in rabbit, with either 1 mM 8-Br-cAMP or 0.1 microM forskolin. Phosphorylation of vimentin increased in the presence of beta-adrenergic agonists and could be blocked by the antiglaucoma beta-adrenergic antagonist timolol. The alpha-adrenergic agonist phenylephrine had no effect on phosphorylation of vimentin. Indirect immunofluorescence microscopy using a monoclonal antibody, anti-vimentin, allowed the localization of vimentin filaments in cultured ciliary epithelial cells. Treatment of these cells in culture with the catecholamine hormone, isoproterenol (1 microM), resulted in a profound reorganization of vimentin filaments. This may be correlated with the enhanced levels of phosphorylated vimentin observed upon increasing cellular cyclic AMP.     

Effect of the Prophage and Penicillinase Plasmid of the Recipient Strain Upon the Transduction and the Stability of Methicillin Resistance in Staphylococcus aureus

Transduction of a methicillin-resistance determinant (mec) in Staphylococcus aureus RN450 was dependent on its prior lysogenization with an appropriate temperate phage. In addition, an appropriate transduced penicillinase plasmid was usually required. Some phage 80-resistant variants of RN450 or of its parental lysogenic strain, NCTC 8325, were also effective recipients for transduction of mec. Elimination of prophage from RN450 abrogated its effectiveness as a transductional recipient of mec. Elimination of prophage from a methicillin-resistant transductant of RN450 reduced resistance to undetectable levels in six of seven phage-eliminated strains. In four of these a variable number of clones again became phenotypically resistant after lysogenization alone or lysogenization combined with reintroduction of a penicillinase plasmid. In two prophage-eliminated strains, no evidence of residual mec could be adduced. The establishment, expression, or stability of the transduced mec in strain RN450 appeared to depend on some function determined by a prophage or a prophage and a penicillinase plasmid.     

Reconstruction of the chondriome of the amastigote form of Trypanosoma cruzi

The chondriome of the amastigote form of Trypanosoma cruzi was studied by fluorescent microscopy using rhodamine 123 and conventional transmission electron microscopy of serial thick sections. The 3-dimensional models of the chondriome generated from the serial sections using manual or computer-assisted analysis revealed a single circular or horseshoe-shaped mitochondrion in each amastigote studied. The morphology of the amastigote chondriome does not conform to that seen in the epimastigote or trypomastigote forms of T. cruzi. Cell shape and mitochondrial form are comparable for a given morphotype, but they differ between cyclical forms.     

Three-dimensional reconstruction of the feeding process of the malaria parasite

The use of serial sectioning followed by three-dimensional (3D) reconstruction is a convenient way to study the spatial morphology of any structure (organ, cell, organelle). This method was applied to the study of the feeding mechanism of some strains of murine and human Plasmodium and enabled clarification of morphological features of this process. The feeding and digestive system of Plasmodium is polymorphic: in single sections, it shows rounded or elongated vesicles or vacuoles of very different sizes and content. The 3D reconstruction allowed us to describe the phenomenon both in space and in time. The contents of the host cell are taken up through the cytostome to form a sausage-shaped cytostomal tube. Individual digestive vesicles are either pinched off from the terminal portion of the tube or by the individualization of the different portions of the tube itself. The cytosomal system can be made of several tubes or vesicles always originating from cytostomes that can disappear when the tube is fully developed. A second feeding mechanism is also observed. Smaller vesicles are formed from the cytostomal vacuoles or tubes, or from the surface of the so-called "food vacuole, " or from the whole erythrocyte/parasite interface. Very few differences appear when the different strains are compared. In the chloroquine-resistant strain of P. berghei or in the P. falciparum FCR3 strain, there appears to be a large increase in the number of cytostomal vesicles, with several functional cytostomes in P. falciparum. The chronology of the appearance of the two systems is comparable between the different species except in P. falciparum, where the pigment vesicles fuse together very rapidly to form a large residual vacuole with which the subsequently formed and degraded digestive vacuoles fuse.     

Effect of flushing of blastocysts on days 10-13 on the life-span of the corpora lutea in the pig

Blastocysts were flushed out of both uterine horns of gilts on Days 10, 11, 12 or 13. In mated non-pregnant gilts flushing had no effect on progesterone profile or cycle length (20.8 +/- 0.4 versus 20.6 +/- 0.6 days in the preflush cycle, N = 6, mean +/- s.e.m.). Flushing the blastocysts out of the uterine horns on Day 10 resulted in a cycle with a normal progesterone profile and a normal length (21.2 +/- 0.4 days, N = 5). Flushing on Days 11, 12 or 13 resulted in a normal cycle or in maintenance of the CL for 3-13 days as indicated by elevated progesterone concentrations and an increased interoestrous interval of, respectively, 22.0 +/- 1.2 versus 19.8 +/- 0.6 days (Day 11; N = 6), 24.8 +/- 1.4 versus 21.0 +/- 0.6 days (Day 12; N = 5; P less than 0.05) and 26.3 +/- 2.3 versus 20.5 +/- 0.4 days (Day 13; N = 6; P less than 0.05). There was a positive relationship between the change in interoestrous interval and the interval between the first observed standing oestrus and flushing of the blastocysts (rs = 0.350; n = 22; P less than 0.1). There was a large variation in the diameter of the blastocysts flushed on the same day. Only in those gilts in which the blastocysts were greater than or equal to 8 mm or filamentous were the CL maintained for 3 or more days. These results indicate that a first signal for maternal recognition of pregnancy is generated on Day 12 and that blastocysts greater than or equal to 8 mm are required for prolongation of CL function for 3 or more days. Since CL function is only extended for a maximum of 13 days (mean 7.4 +/- 1.0), a second signal seems necessary to maintain the CL for the whole period of pregnancy.     

Evidence for a role of the cytoskeleton in the in vitro folliculogenesis of the thyroid gland of the fetal rat

Summary Thyrotropic hormone (TSH) or cAMP accelerate the formation of follicular cavities in the explanted thyroid gland of the 15-day-old rat fetus. Cytochalasin B or vinblastine and nocodazole or colchicine, which disorganize microfilamental and microtubular structures respectively, inhibit or completely block in vitro-induced folliculogenesis. Exposure of the thyroid tissue to lumicolchicine, a structural isomer of colchicine deprived of antimicrotubular activity, does not inhibit the activation of folliculogenesis induced by TSH. These results are strong evidence for the supposition that microfilaments and microtubules are involved in the TSH-stimulated mechanisms resulting in thyroid folliculogenesis. Folliculogenesis requires the integrity of both microfilaments and microtubules.