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PubMed1997

Alzheimer's disease: transiently developing dendritic changes in pyramidal cells of sector CA1 of the Ammon's horn.

In the course of Alzheimer's disease, specific CA1 pyramidal cells develop dendritic changes, which can only be observed transiently. Distal segments of the apical dendrite running through the stratum lacunosum-moleculare show spindle-shaped dilations filled with abnormal tau protein. The alteration eventually leads to amputation of the changed segment. The damage first appears at stage II in the evolution of the neurofibrillary changes [5], is best developed at stage III, and vanishes from the tissue at stage IV. It is usually not observed in stages V and VI (fully developed Alzheimer's disease).

Adult↗
PubMed2001

Platelet-derived growth factor and transforming growth factor-beta in invertebrate immune and neuroendocrine interactions: another sign of conservation in evolution.

Growth factor-like molecules have been found in various invertebrate species. In particular, we have reported the presence of platelet-derived growth factor (PDGF)-AB and transforming growth factor-beta (TGF-beta)1 immunoreactive molecules in molluscs, insects and annelids. Moreover, PDGF-AB and TGF-beta1 affect the main immune functions, such as phagocytosis, chemotaxis and cell motility. Changes in cell shape are induced via interactions of growth factors with their respective specific receptors. The extracellular signals are transduced by the activation of classical signal transduction pathways, such as those involving PKA and PKC, and pivotal transcription regulators, i.e. the Fos, Jun and SMAD proteins. The two growth factors intervene in stress responses by activating the CRH-ACTH-biogenic amine axis. Exogenous administration of PDGF-AB and TGF-beta1 in a molluscan wound provokes an accelerated migration of immunocytes and fibroblasts to the injured area, stimulating granulation tissue formation and wound re-epithelialization. These findings suggest that these molecules are ancestral and that their function is well conserved and crucial in the maintenance of invertebrate homeostasis.

Animals↗
PubMed1987

Effect of changes in neurofilament content on caliber of small axons: the beta,beta'-iminodipropionitrile model.

The structural role of neurofilaments in the normal axon and the consequences of altered axonal transport of neurofilaments have been extensively studied in large axons. These studies suggest that neurofilament numbers and interneurofilament spacing are major determinants of axonal cross-sectional area. In contrast, in small axons and dendrites, microtubules and membranous organelles appear to be the most closely correlated with size and shape of the cell process. In this study we have examined the effect of impairment in neurofilament transport on small axons, typical of most CNS pathways. Neurofilament transport was impaired by administration of beta,beta'-iminodipropionitrile (IDPN), resulting in proximal accumulation and distal depletion of neurofilaments. The evolution of these changes was studied in the optic nerves of guinea pigs treated with IDPN, 1-35 weeks following intoxication. The effect of this redistribution of neurofilaments on cross-sectional area of small axons was evaluated using quantitative ultrastructural methods. Our results show that with the alteration in neurofilament transport seen with IDPN intoxication, there is a wide spectrum of neurofilament densities, ranging from a 5-fold increase above normal in the proximal axon, to a 5-fold decrease below normal in the distal axon. Although the optic nerve fibers enlarge with the increase in neurofilament content, they do not atrophy significantly with the continued loss of neurofilaments. We conclude that factors other than neurofilament content are capable of maintaining size and shape of these small axons. Candidate organelles include microtubules and membranous organelles and possibly other axonal elements.

Animals↗
PubMed2000

Molecular evolution of color vision of zebra finch.

We have isolated and sequenced the RH1(Tg), RH2(Tg), SWS2(Tg), and LWS(Tg) opsin cDNAs from zebra finch retinas. Upon binding to 11-cis-retinal, these opsins regenerate the corresponding photosensitive molecules, visual pigments. The absorption spectra of visual pigments have a broad bell shape, with the peak being called lambda(max). Previously, SWS1(Tg) opsin cDNA was isolated from zebra finch retinal RNA, expressed in cultured COS1 cells, reconstituted with 11-cis-retinal, and the lambda(max) of the resulting visual pigment was shown to be 359nm. Here, the lambda(max) values of the RH1(Tg), RH2(Tg), SWS2(Tg), and LWS(Tg) pigments are determined to be 501, 505, 440, and 560nm, respectively. Molecular evolutionary analyses suggest that specific amino acid replacements in the SWS1 and SWS2 pigments, resulting from accelerated evolution, must have been responsible for their functional divergences among the avian pigments.

Amino Acid Sequence↗
PubMed1995

Evolution and ultrastructure of the bovine spermatogonia precursor cell line.

The spermatogonial stem cell line in prepubertal and adult bovine testis was studied by electron microscopy and protein gene product 9.5 immunohistochemistry. Three successive spermatogonia precursor cell configurations were observed. Small basal stem cells were found to possess a spherical shape and nuclei with two to three nucleoli. They were observed in prepubertal testes (25 and 30 weeks) and in low numbers during all the stages of the seminiferous epithelial cycle in the adult. Aggregated spermatogonia precursor cells are the dominating germ cell type in the 25-week-old and 30-week-old calf. In the adult seminiferous epithelium, they cause expansion of the basal tubular compartment as they form dense groups containing up to 15 cells. These groups are observed concomitantly with cycling A-spermatogonia and preleptotenes at the beginning of spermatocytogenesis. At the end of A-spermatogonia propagation, the aggregated spermatogonia precursor cells separate and intermingle with cycling A-spermatogonia. The spermatogonia precursor cells can later be found together with I-spermatogonia as members of an interconnected cellular network of medium-sized cells. When the I-spermatogonia divide to form the smaller B-spermatogonia, the precursor cells, which stay connected with the cycling spermatogonial population, pass through a growth phase. They can now be considered as committed spermatogonia precursor cells and are continuously being transformed into A1-spermatogonia to start a new round of spermatocytogenesis. Ultrastructurally, all members of the precursor cell line are similar. However, a number of features have been found to show a quantitative increase (endoplasmic reticulum, mitochondria) or to exhibit a rising degree of complexity (nucleolus) during the progression from basal stem cells to committed spermatogonia precursor cells.

Animals↗
PubMed1991

Afterpotential characteristics and firing patterns in maturing rat hippocampal CA1 neurones in in vitro slices.

The postnatal evolution of depolarizing after-potentials (DAPs) and after-hyperpolarizations (AHPs) was studied in rat CA1 hippocampal neurones (5-68 days of age) using in vitro slices. Results were pooled into 4 age groups: P5-9, P10-16, P17-24 and P26-68. In P5-9 cells, DAPs were seen as passive signals, with a time constant similar to the time constant of the membrane. The evolution of the DAP was characterized by a decrease in amplitude, an increase in duration and a change in contour. In P10-16 and P17-24 cells, the DAPs often had a plateau or a hump-like shape which increased the probability of firing and the occurrence of spike doublets. The firing pattern and bursting behaviour of P10-16 CA1 neurones differed from the pattern typical of the adult. P5-9 and P10-16 cells had post-burst AHPs with a smaller amplitude and a more prolonged early phase than at late stages of development.

Action Potentials↗
PubMed2001

Neurogenesis in the developing visual system of the branchiopod crustacean Triops longicaudatus (LeConte, 1846): corresponding patterns of compound-eye formation in Crustacea and Insecta?

In the discussion on arthropod phylogeny, the structural evolution of compound eyes and optic ganglia in Crustacea and Insecta is an important topic. On the one hand, many morphological features as well as developmental aspects of the visual system in Insecta and Crustacea correspond in so much detail that eye design in these two groups is likely to have a common euarthropodan ancestor. On the other hand, however, some authors advocate a convergent evolution of the crustacean and insect visual system founding their arguments on differences in the arrangement of the visual neuropils and the fibre connections between Malacostraca and Entomostraca (the "entomostracan enigma"). Therefore, information about cellular aspects of visual system formation in entomostracan Crustacea is likely to enliven this debate, but is not yet available. To fill this gap, we examined the proliferation of neuronal stem cells in the developing visual system of the tadpole shrimp Triops longicaudatus (LeConte, 1846) (Entomostraca, Branchiopoda, Phyllopoda, Calmanostraca, Notostraca) by in vivo incorporation of the proliferation marker bromodeoxyuridine and subsequent immunohistochemical detection. Our results indicate that in the developing visual system of T. longicaudatus, three band-shaped zones containing neuronal stem cells are present corresponding to the proliferation zones found in Malacostraca. We therefore conclude that the ontogenetic mechanisms of visual-system formation are evolutionarily conserved (homologous) in Branchiopoda, Malacostraca, and Insecta.

Animals↗
PubMed1997

An epidemic of tuberculosis with a high rate of tuberculin anergy among a population previously unexposed to tuberculosis, the Yanomami Indians of the Brazilian Amazon.

A survey of an emerging tuberculosis epidemic among the Yanomami Indians of the Amazonian rain forest provided a unique opportunity to study the impact of tuberculosis on a population isolated from contact with the tubercle bacillus for millennia until the mid-1960s. Within the Yanomami population, an extraordinary high prevalence of active tuberculosis (6.4% of 625 individuals clinically examined) was observed, indicating a high susceptibility to disease, even among bacille Calmette-Guérin-vaccinated individuals. Observational studies on cell-mediated and humoral immune responses of the Yanomami Indians compared with contemporary residents of the region suggest profound differences in immunological responsiveness to Mycobacterium tuberculosis infection. Among the Yanomami, a very high prevalence of tuberculin skin test anergy was found. Of patients with active tuberculosis, 46% had purified protein derivative of tuberculosis reactions <10 mm; similarly 58% of recent bacillus Calmette-Guérin vaccines exhibited skin test reactions <5 mm. The Yanomami also had higher titers of antibodies against M. tuberculosis glycolipid antigens (>70%) than the control subjects comprised of Brazilians of European descent (14%). The antibodies were mostly of the IgM isotype. Among the tuberculosis patients who also produced IgG antibodies, the titers of IgG4 were significantly higher among the Yanomami than in the control population. Although it was not possible to analyze T-cell responses or patterns of lymphokine production in vitro because of the remoteness of the villages from laboratory facilities, the results suggest that the first encounter of the Yanomami Indian population with tuberculosis engenders a diminished cell-mediated immune response and an increased production antibody responses, relative to other populations with extensive previous contact with the pathogen. These findings suggest that tuberculosis may represent a powerful selective pressure on human evolution that over centuries has shaped the nature of human immune responses to infection.

Antibodies, Bacterial↗
PubMed1975

[Morphogenesis of the chick embryo foot].

Observations were made on chick embryo feet between 6 and 12 1/2 days of incubation in order to (a) give a precise description of programmed cell death in the interdigital membranes; (b) correlate the evolution of interdigital necrosis with the differentiation of the cartilaginous phalangeal skeleton; (c) measure the relative growth rates of digits and interdigits. The programme of interdigital cell death proceeds in three phages which comprise the appearance, the extension and the disappearance of necrotic areas. Fourteen distinct stages are described. The evolution of programmed cell death can be strictly correlated to the chondrogenesis of successive phalanges, in the sense that each stage of necrosis (except two of them) differs from the preceding one by the differentiation of an additional phalanx. Shaping of the foot results from differential growth rates and proceeds in three phases, the second of which is characterized, between days 8 and 10 of incubation, by the actual shortening (decrease of absolute length) of the interdigital membranes. These observations are compared to those that were previously made on other avian and mammalian species and the morphogenetic role of programmed cell death is discussed in the light of that comparison.

Animals↗
PubMed1976

[Homoplastic transplantation of crayfish testes (Pontastacus leptodactylus leptodactylus (Eschscholtz, 1823)) in sexual rest into normal and destalked males and females: preliminary results].

Implantation of Crayfish testes in sexual rest into females leads to a new onset of spermatogenetic activity characterized by a precocious appearance of spermatocytes. However, these cells degenerate: their evolution never goes further than the pachytene stage of meiosis prophase. Abortive prophases appear continuously; this also takes place in acini which develop secondarily. Implantation of testes in sexual rest into males in the same physiological shape also leads to the precocious appearance of primary spermatocytes blocked in prophase of meiosis. However, the transplant tends to reacquire a structure similar to the one of a normal resting testis. The delay of appearance of the first spermatocytes is always shortened--less than a month instead of one month and a half--if the receptive female is destalked at the time of the implantation or if the donor male has been destalked one month before the transplantation. The interpretation of the observed phenomena is discussed.

Animals↗
PubMed2000

How important is DNA replication for mutagenesis?

Rates of mutation and substitution in mammals are generally greater in the germ lines of males. This is usually explained as resulting from the larger number of germ cell divisions during spermatogenesis compared with oogenesis, with the assumption made that mutations occur primarily during DNA replication. However, the rate of cell division is not the only difference between male and female germ lines, and mechanisms are known that can give rise to mutations independently of DNA replication. We investigate the possibility that there are other causes of male-biased mutation. First, we show that patterns of variation at approximately 5,200 short tandem repeat (STR) loci indicate a higher mutation rate in males. We estimate a ratio of male-to-female mutation rates of approximately 1.9. This is significantly greater than 1 and supports a greater rate of mutation in males, affecting the evolution of these loci. Second, we show that there are chromosome-specific patterns of nucleotide and dinucleotide composition in mammals that have been shaped by mutation at CpG dinucleotides. Comparable patterns occur in birds. In mammals, male germ lines are more methylated than female germ lines, and these patterns indicate that differential methylation has played a role in male-biased vertebrate evolution. However, estimates of male mutation bias obtained from both classes of mutation are substantially lower than estimates of cell division bias from anatomical data. This discrepancy, along with published data indicating slipped-strand mispairing arising at STR loci in nonreplicating DNA, suggests that a substantial percentage of mutation may occur in nonreplicating DNA.

Animals↗
PubMedDate not supplied

Coccidioidomycosis in Brazil. A case report.

UNLABELLED: Coccidioidomycosis is an endemic infection with a relatively limited geographic distribution: Mexico, Guatemala, Honduras, Colombia, Venezuela, Bolivia, Paraguay, Argentina and the southwest of the United States. In these countries, the endemic area is restricted to the semiarid desert like regions which are similar to the northeast of Brazil. CASE REPORT: The patient is a 32 year-old male, born in the state of Bahia (Northeast of Brazil) and has been living in São Paulo (Southeast) for 6 years. He was admitted at Hospital das Clínicas, at the Department of Pneumology in October 1996, with a 6 month history of progressive and productive cough, fever, malaise, chills, loss of weight, weakness and arthralgia in the small joints. Chest x-rays and computerized tomography disclosed an interstitial reticulonodular infiltrate with a cavity in the right upper lobe. The standard potassium hydroxide preparation of sputum and broncoalveolar lavage demonstrated the characteristic thickened wall spherules in various stages of development. Sabouraud dextrose agar, at 25 degrees C and 30 degrees C showed growth of white and cottony aerial miceleium. The microscopic morphology disclosed branched hyphae characterized by thick walled, barrel shaped arthroconidia alternated with empty cells. The sorological studies with positive double immunodiffusion test, and also positive complement fixation test in 1/128 dilution confirmed the diagnosis. The patient has been treated with ketoconazole and presents a favorable clinical and radiological evolution.

Adult↗
PubMed1994

Recent approaches in the analysis of weightlessness effects on arthropod development.

The concept of Biological Development refers to the extremely complex process by which every biological organism reproduces starting from a huge single cell, the fertilized egg. It includes all aspects of cellular and intercellular structure and function. In spite of many recent advances, especially at the molecular and genetical level, we are still far from fully understanding the details and mechanisms at work in developmental systems. It is even unclear what physical mechanisms are used by the different molecular components resulting in the emergence of these higher levels of organization. Newman and Comper, have extensively discussed the "generic" physical forces potentially involved in pattern formation, arguing that among others, gravitational effects could be involved in the production of cytoplasmic, tissue and extracellular matrix components rearrangements playing a role in morphogenesis. Although plagued with the problem of being a very weak force, specially at the tiny dimensions of cells, gravity is one of the "generic" physical forces that have been continuously operating on biological organisms during evolution. Few scientists would argue against the idea that at least in the early times of evolution, gravity could have been involved in shaping the spatial inhomogeneities behind the initial phases of development.

Animals↗
PubMed2025

Origin and evolution of mitochondrial inner membrane composition.

Unique membrane architectures and lipid building blocks underlie the metabolic and non-metabolic functions of mitochondria. During eukaryogenesis, mitochondria likely arose from an alphaproteobacterial symbiont of an Asgard archaea-related host cell. Subsequently, mitochondria evolved inner membrane folds known as cristae alongside a specialized lipid composition supported by metabolic and transport machinery. Advancements in phylogenetic methods and genomic and metagenomic data have suggested potential origins for cristae-shaping protein complexes, such as the mitochondrial contact site and cristae-organizing system (MICOS). MICOS protein homologs function in the formation of cristae-like intracytoplasmic membranes (ICMs) in diverse extant alphaproteobacteria. The machinery responsible for synthesizing key mitochondrial phospholipids - which cooperate with cristae-shaping proteins to establish inner membrane architecture - could have also evolved from a bacterial ancestor, but its origins have been less explored. In this Review, we examine the current understanding of mitochondrial membrane evolution, highlighting distinctions between prokaryotic and eukaryotic mitochondrial-specific proteins and lipids and their differing roles in shaping cristae and ICM architecture, and propose a model explaining the concurrent specialization of the mitochondrial lipidome and inner membrane structure in eukaryogenesis. We discuss how advancements across a range of disciplines are shedding light on how multiple membrane components co-evolved to support the central functions of eukaryotic mitochondria.

Mitochondrial Membranes↗
PubMed1976

The subacrosomal granule and its evolution during spermiogenesis in a lizard. Observations about the acrosomal fringe and the spermatid-sertoli cell relationship.

Some aspects of spermiogenesis have been studied in the testis of the teiid lizard Cnemidophorus lemniscatus lemniscatus by electron microscopy. Shortly after the acrosomal vesicle is lodged in a nuclear concavity of the spermatid, a dense granule differentiates in the center of the subacrosomal space. It is cone-shaped and shows a longitudinal striation. Its base applies to the acrosomal membrane and, through this, to the acrosomal granule. Its rounded vertex causes a depression of the nuclear membranes which, initially juxtaposed, separates at this point to form a vesicle. The granule develops and becomes a rod when spermiogenesis is advanced and the subacrosomal space has taken the form of a secondary cap. The rod is cylindrical, retains its original striation and has a convex acrosomal end. It encloses the vesicle formed by the nuclear envelope in its base and follows the apex of the nucleus. Meanwhile, the acrosomal granule loses its identity and the acrosomal cap is filled with a dense substance, in which a fringe of translucent material differentiates. This fringe lies in the dorsal and apical margins of the acrosome and is incompletely divided by longitudinal crests of the dense acrosomal substance. A projection of the Sertoli cell forms an accessory cap which envelops the acrosome and is in turn covered by the cytoplasm of the spermatid, constituting an intricate association. Two reflex membranes underlie the plasmalemma in the outer surface of the projection of the Sertoli cell. They are continuous with one another at their ends and with the cell membrane in the edge of pores. In the peripheral cytoplasm of the spermatid facing the accessory cap, numerous microtubules run longitudinally. By means of thin membranes some are interconnected or connected with the plasmalemma, from which they seem to originate.

Acrosome↗
PubMed1983

A thermodynamic study of sperm-egg interaction.

We have studied the binding of spermatozoa to the receptor sites on the vitelline coat (VC) of glycerol-treated eggs (ghost eggs) of the Ascidian, Ciona intestinalis (Protochordate). Glycerol treatment cytolyses the egg without affecting the ability of the VC to bind spermatozoa in a species-specific manner; however, in this system binding is not followed by the acrosome reaction. The ghost eggs are metabolically inert. As a base line for our analysis, we have studied the concentration-dependent heat evolved and oxygen consumption of spermatozoa when diluted in sea water. The process has been analyzed on the basis of equations derived by Liquori and Tripiciano to describe cell growth. Upon binding to the ghost eggs, the spermatozoa produce an explosive heat evolution (excess heat) which is not accompanied by oxygen consumption. The excess heat produced plotted against sperm concentration (at constant egg concentrations) gives an asymmetric bell-shaped curve. This is interpreted as being due to the competitive effect of sperm agglutination at a high sperm concentration. It is concluded that only spermatozoa that attach singly (monomeric spermatozoa) to the egg undergo metabolic activation.

Animals↗
PubMed1993

The cytological spectrum of the monocytoid B-cell reaction: recognition of its large cell type.

To analyse the cytological features of benign monocytoid B-cells, we investigated, histologically and immunohistochemically, 78 reactive lymphadenopathies expressing monocytoid B-cell reactions. Within a broad cytological spectrum of reactive monocytoid B-cells, two cytological types can be recognized: 1 the common type composed of medium-sized cells with irregular or bean-shaped nuclei and inconspicuous nucleoli, and 2 the large cell type composed of cells considered to represent large transformed monocytoid B-cells, with less pleomorphic round nuclei with vesicular chromatin and moderately basophilic, prominent nucleoli. In between these variants transitional forms showing evolution to large transformed monocytoid B-cells occurred. While monocytoid B-cell reactions in 70.5% of all cases were composed predominantly of the common type of monocytoid B-cells, in 29.5% of cases the large transformed cells prevailed. The two distinctive cytological types of reactive monocytoid B-cells seem to have their neoplastic counterparts in monocytoid B-cell lymphoma, including its large cell variant.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1989

Sound localization, use of binaural cues and the superior olivary complex in pigs.

Noise localization thresholds and the ability to localize pure tones at 60 degrees separation were determined for three domestic pigs using a conditioned avoidance procedure. The average threshold for localizing a brief noise burst was 4.5 degrees which is much more accurate than the thresholds of other hoofed mammals, such as horses, cattle and goats. The ability of pigs to localize low-frequency tones indicates that they can use the binaural phase-difference cue. However, they were unable to localize tones of 4 kHz and higher, indicating that, like other hoofed mammals, their ability to use binaural intensity cues is greatly restricted if not completely absent. An examination of the superior olivary complex of pigs revealed that in relative size, shape and cell density it is more like that of cats than that of other hoofed mammals.

Animals↗