Histology of Organogenic and Embryogenic Responses in Cotyledons of Somatic Embryos of Quercus Suber L.

In cork oak (Quercus suber L.), recurrent embryogenesis is produced in vitro through autoembryony without exogenous plant growth regulators (PGRs); secondary embryos appear on the embryo axis but seldom on cotyledons. Focusing mainly on the histological origin of neoformations, we investigated the influence of the embryo axis and exogenous PGRs on the embryogenic potential of somatic embryo cotyledons. Isolated cotyledons of somatic embryos became necrotic when cultured on PGR-free medium but gave secondary embryos when cultured on media containing benzyladenine and naphthaleneacetic acid. Cotyledons of cork oak somatic embryos are competent to give embryogenic responses. Isolated cotyledons without a petiole showed a lower percentage of embryogenic response than did those with a petiole. In petioles, somatic embryos arose from inner parenchyma tissues following a multicellular budding pattern. Joined to the embryo axis, cotyledons did not show morphogenic responses when cultured on PGR-free medium but revealed budlike and phylloid formations when cultured on medium with PGRs. The different morphogenic behavior displayed by somatic cotyledons indicates an influence of the embryo axis and indicates a relationship between organogenic and embryogenic regeneration pathways.

Large accumulation of mRNA and DNA point modifications in a plant senescent tissue.

Although nucleic acids are the paradigm of genetic information conservation, they are inherently unstable molecules that suffer intrinsic and environmental damage. Oxidative stress has been related to senescence and aging and, recently, it has been shown that mutations accumulate at high frequency in mitochondrial DNA with age. We investigated RNA and DNA modifications in cork, a senescent plant tissue under high endogenous oxidative stress conditions. When compared to normally growing young tissue, cork revealed an unexpected high frequency of point modifications in both cDNA (Pn = 1/1784) and nuclear DNA (Pn = 1/1520). Cork should be viewed as a mosaic of genetically heterogeneous cells. This has biological implications: it supports somatic mutation models for aging and challenges 'single cDNA clone' as descriptor for the molecular genetics of senescent tissues.

Influence of weather on cork-ring width.

Ring-width series of cork from Quercus suber L. trees growing at two sites in Extremadura (southwestern Spain) were analyzed in relation to monthly precipitation and temperature, and to climatic indices combining both variables. Ring width of cork showed strong positive correlations with precipitation, especially during the fall and winter. Moderately low temperatures were favorable for cork growth, except in winter and during the onset of phellogen activity. We conclude that drought or temperature, or both, can limit cork growth during the annual drought period.

Wound healing after silver nitrate burns in the leech hirudo medicinalis

The healing process after inflicting silver nitrate burns, a type of injury in which a heavy loss of body wall tissues occurs, was studied in Hirudo medicinalis. Silver solution penetrates the body wall and silver precipitates in the tissues during infiltration. Vasocentral cells, do not penetrate the impregnated zone but accumulate just below it to form a pseudoblastema. The impregnated zone splits off entirely, leaving an area covered by pseudoblastema cells on the leech surface, which is progressively reepithelialized. There is no regeneration of the lost body region, and although some connective tissue matrix may be produced by pseudoblastema cells, there is no significant regeneration of the connective tissue and nor the muscular fibers of the body wall, resting an evident depression in the damaged zone. The amount of affected tissue, and possibly the inability of vasocentral cells to reach the infiltrated tissues are determinant factors in the development of the splitting process. Copyright 1999 Academic Press.

The pseudoblastema in the wound healing process of the leech Hirudo medicinalis L. (Hirudinea): changes in cell junctions.

The role of the connective tissue cells and their migratory behavior have been investigated in the formation and evolution of the pseudoblastema during wound healing in the leech Hirudo medicinalis. In H. medicinalis the healing process shows first a flow of cells that effectively seal the wound and form a temporary cellular clump, the pseudoblastema, which contributes to the phagocytotic process and apparently regenerates the extracellular matrix. The migratory cells forming the pseudoblastema are connective tissue cells known as vasocentral cells, which, when in a resting state, are associated with the vasofibrous cells. During the formation and evolution of the pseudoblastema several changes affect vasocentral cell junctions. At rest, vasocentral cells do not show cell to cell junctions but they show adhering junctions in contact with the extracellular matrix. These junctions disrupt during the migratory phase. When vasocentral cells regroup in the pseudoblastema, adhering junctions are formed between them, and adhering junctions making contact with the matrix appear again. As the pseudoblastema evolves, cell to cell adhering junctions become more conspicuous and undergo other changes. During the next stage of retraction, close contacts develop between pseudoblastema cells and neighboring nondamaged muscle fibers, which probably serve as points of anchorage for the approaching movement of the wound edges. Finally, cell to cell and cell to matrix junctions disappear and the pseudoblastema disintegrates.

Ultrastructure and cytochemistry of secretory cells in the skin of the leech, Dina lineata.

The ultrastructure and histochemical features of the two types of secretory cells in leech skin are described. Pear-shaped cells secrete mucus containing carboxylated mucosubstances, while tubular cells produce a mucus containing a mixture of neutral, carboxylated, and sulfated mucosubstances. Pear-shaped secretory cells have two types of neuroglandular junctions, one containing dense-core serotonergic vesicles and the other small clear vesicles. Tubular secretory cells have large terminals, with many clear vesicles thought to be cholinergic. © 1993 Wiley-Liss, Inc.

Changes in epithelial cells in Hirudo medicinalis during wound healing.

In the leech, Hirudo medicinalis, reepithelialization is an event which takes place early in the wound healing process, immediately after the formation of the pseudoblastema, 4-8 hr postinjury. Epithelial cells on the wound margins move into the wound, modifying their phenotypic characteristics. Cells lose their columnar shape and become flattened. Dermal junctions disrupt and tonofilaments regroup around the nucleus. Then, the epithelial cell sheet moves over the newly formed pseudoblastema by extending filopodia, formed by the cells on the edge, following the so-called "sliding model." When the wound is fully covered by the new epithelium, about 24 hr postinjury, a reorganization of the cytoskeleton occurs and the basal dermal junctions are reconstructed. Six days postinjury, the epidermal cells return to their original columnar shape.

Heparin-induced hyperkalemia: a prospective study.

Heparin is frequently used for the prophylaxis and treatment of deep venous thromboembolism and it induces hypoaldosteronism leading to hyperkalemia, an uncommon adverse effect. In an intensive prospective drug monitoring study, 154 inpatients at the Internal Medicine Unit of Hospital Sotero del Río, Santiago, Chile, received heparin in the period between March and November 1990. Mean age of the patients was 65.8 +/- 12.9 years and 56.5% were female. Twenty-one (13.6%) patients developed heparin-induced adverse reactions. Thirteen events were hyperkalemia, 7 ecchymoses and 1 hematuria. The monitoring team and attending physicians have agreed to classify 9 heparin-induced hyperkalemia cases as probable and the other 4 as possible. No adverse reaction was fatal but 8 of the patients had severe hyperkalemia. Almost all reactions were dose-related. Hyperkalemia was more frequent in patients with diabetes mellitus, metabolic acidosis and long-term heparin therapy. The frequency of hyperkalemia did not correlate with age, sex, renal impairment or with previous use of anti-inflammatory drugs, heparin or aspirin.

Ultrastructure of the sperm and spermatogenesis and spermiogenesis of Dina lineata (Hirudinea, Erpobdellidae).

The mature sperm of Dina lineata is of the modified type. The sperm are 48 micron long and 0.3 micron wide. The sperm are filiform and helicoidal cells with a distinct head, a midpiece, and a tail. There are two distinct regions in the head: the acrosome and the posterior acrosome, each with its own characteristic morphology. The midpiece is the mitochondrial region and has a single mitochondrion. Two distinct portions can be observed in the tail: the axonematic region and the terminal piece. In the process of spermatogenesis the early spermatogonia divide to form a poliplast of 512 spermatic cells. In the spermiogenesis the following sequential stages can be distinguished: elongation of the flagellum; reciprocal migration of mitochondria and Golgi complex; condensation of chromatin and formation of the posterior acrosome; spiralization of nuclear and mitochondrial regions; and, finally, formation of the anterior acrosome. The extreme morphological complexity of the Dina spermatozoon is related to the peculiar hypodermal fertilization which characterizes the erpobdellid family. Correlation between sperm morphology and fertilization biology in the Annelida is revised.

Diagnóstico de tumores primitivos y metastásicos del hígado en medicina nuclear. Presentación de los resultados de tres métodos / Diagnosis of primitive and metastasic tumors of the liver in nuclear medicine. Presentation of results of three methods

Se estudian dos series de pacientes con el fin de evaluar los resultados de los tres métodos empleados por la medicina nuclear en la obtención e informe de imágenes hepáticas que sirven para la detección de tumores primitivos y metastásicos. La especificidad y exactitud obtenidas en las vistas estáticas, en la cámara gamma y la tomografía hepática de emisión son superiores a las obtenidas en el gammatopógrafo lineal. Se hacen recomendaciones para la indicación de los mismos(AU)

Tomografía hepática por emisión / Emission tomography of the liver

Se presenta una serie de 100 pacientes en los que se analizan las causas de diagnóstico falso positivo en 7 pacientes, de los cuales 5 se debió a una interpretación errónea del corte tomográfico por no tener presente el nivel ni la profundidad de los mismos. Se analizan las 7 causas del diagnóstico falso positivo (AU)

Tomografía hepática de emisión: estudio de 176 pacientes con tumores primitivos conocidos / Emission tomogrphy of the liver: study of 276 patients with known primitive tumors

Se presenta el estudio de 176 pacientes a los que se le realizaron tomografía hepática de emisión. En 36 pacientes se diagnosticó la presencia del tumor hepático por métodos anatómicos o evolución clínica que presentaron una sensibilidad de 75,0 porciento. De éstos 36pacientes a 25 se les realizó ecografía que mostró una sensibilidad de 80,0 porciento, mientras que los 31 pacientes con exámenes de laboratorio clínico la sensibilidad fue de 51,6 porciento. La especialidad de los 140 pacientes de la tomografía de emisión y de los 81 de estos pacientes ue se les había realizado ecografía fueron muy similares. La tomografía de emisión permitió realizar un diagnóstico correcto en 9 pacientes, 7 de los cuales tenían imágenes estáticas dudosas y 2 negativas, con una contribución de 5,1 porciento (AU)

La tomografía hepática de emisión y la ecografía hepática. Estudio comparativo / Hepatic emission tomography and hepatic echography. Comparative study

Se realizó un estudio comparativo en 106 pacientes con tumor maligno primitivo conocido, entre la tomografía hepática de emisión y la ecografía, y esta última tuvo una sensibilidad, especificidad y exactitud discretamente más elevada. Son analizadas las causas que motivaron errores en el diagnóstico. Se concluye que ambas técnicas se complementan, no se excluyen (AU)

[Bacteriuria detection by dip-slide test (author's transl)]. / Note sull'impiego delle strisce reattive nella determinazione della batteriuria.

A new dip-inoculum method markated as Microstix for detecting bacteriuria was studied to evaluate its usefulness as a screening procedure. This test was found to be reliable when compared with the standard pour plate method. However, antimicrobial agents often present in the urine samples rendered this procedure unsuitable for indiscriminate application in large hospital laboratories. This technique might conceivably be employed in mass screening programs where urine specimens are less likely contamined by antimicrobial drugs.

[Further researches on antimicrobial agents involvement in urine bacteriological analysis (author's transl)]. / Ulteriori ricerche sull'influenza di agenti antimicrobici nell'analisi batteriologica delle urine

A further investigation on about 2700 urine samples for testing the presence of antimicrobial drugs (spot-test) has been carried out. Bacteriostatic agents were present in 35% of all samples analysed, Of these, 47% were urines producing no growth on culturing, 10% had a bacterial count of 10(4) and 43% of 10(5) or more. The frequency of the spot-test positive samples was correlated to the origin from the different Hospital Departments. Gram-positive bacteria were the most represented in the samples without antimicrobial agents, while the frequency of Pseudomonas aeruginosa rised in samples with antimicrobial drugs. Under both conditions no significant variation in the antibiotic-sensitivity pattern was noted in organisms isolated from the urines. Only indole-positive Proteus appeared to be more sensitive when isolated from samples containing no antimicrobial agents.