Sister-chromatid exchange formation at supra-optimal growth temperatures

The present research was mainly focused on characterizing the formation of sister-chromatid exchanges at both optimal and supra-optimal growth temperatures. Under these conditions (25, 30 and 35 degrees C) meristem cells of Allium cepa L. exhibited a roughly constant cell-cycle time, and modifications in other cell-cycle parameters were negligible. Second-division chromosomes of cells incubated at 30 and 35 degrees C showed increased SCE yields as compared with those detected in cells maintained at the optimal temperature (25 degrees C). When cells with unifilarly BrdUrd-substituted DNA was damaged by irradiation with visible light, we obtained almost the same SCE yields at the various temperatures tested. We suggest that this production of SCEs could be the result of a reduced number of lesions produced by light (perhaps as a consequence of reduced intracellular free oxygen at high temperature) and/or of an increased efficiency in the repair capacity of the cells at these temperatures. The analysis of SCE formation in undamaged cells incubated at different temperatures during BrdUrd treatment has shown that the optimal growth temperature appears to be the experimental condition in which the cells are able to exhibit the lowest frequency of SCE.

[Gastroenteritis caused by Campylobacter jejuni in childhood]

Fifteen patients with stool growth of "Campylobacter jejuni" are presented. In one case it was associated with growth of "Salmonella typhimurium". Fourteen cases presented as an acute gastroenteritis whereas the remainder case was considered to be an asymptomatic carrier. The incidence was 5.8%. The disease was more frequent in infancy (13 cases occurred in ages below one year). Diarrhea was the most frequent symptom (93.3%), with presence of macroscopic blood in the stool in 78.5% of these cases. In three cases the process was associated to cow's milk protein-sensitive enteropathy. Four patients were treated with erythromycin and the stool culture become negative at the end of therapy. In the untreated cases the stool culture become negative within a period from five to 15 days. In the asymptomatic carrier the stool culture become negative after a period of two months.

Oxygen dependence of sister-chromatid exchanges

We have studied the dependent of sister-chromatid exchange (SCE) production on the presence of oxygen during incubation of cells in 5-bromodeoxyuridine (BrdUrd) by analyzing the SCE yields in second-division chromosomes of Allium cepa L. meristem cells. We considered the cases between 10 and 100% oxygen in the incubation medium. Under these experimental situations no significant modifications in cell-cycle duration were obtained. Our results lead us to conclude that: (1) in oxygenated treatments, cells incubated during 2 consecutive cycles in the presence of BrdUrd show significantly higher SEC frequencies (in second-division chromosomes) than those treated only during the first cycle; (2) SCE frequencies increase as a function oxygen tension; and (3) oxygen-dependent SCE frequencies increase as a function of oxygen tension and (3) oxygen-dependent SCes appear to be found by exchanging post-replicative DNA portions. These observations suggest that the experimental protocol reported here could be useful in determining both the precise moment of action of an agent during the cell cycle and the DNA portions actively involved in physically and chemically provoked SCEs.

Approximation of baseline and BrdU-induced SCE frequencies

In the present paper we have developed a new rationale and an experimental schedule to approximate the frequency of SCEs which occur independently of BrdU incorporation, namely, the baseline frequency of SCEs. The method used includes the analysis of SCE yields in second and third division chromosomes after BrdU-substitution for 1, 2, and/or 3 successive replication rounds in the presence of this thymidine analogue, leading to a set of ten different experimental results. As a result of formulating various mathematical equations and applying them to the data, an accurate estimation of the frequency of baseline (BrdU-independent) and BrdU-induced SCEs, can be made, thus avoiding the difficulties inherent in the current extrapolation methods. The conclusions are that 1) SCEs seem to be formed after DNA synthesis (by exchanging post-replicative DNA portions), but, obviously, very near to the replication fork and 2) that under our experimental conditions about 0.065 SCEs per picogram of DNA per cell cycle occur as a consequence of chromosome replication, this frequency being increased by BrdU-substitution. The methodology seems to be reliable enough to be used in other species and systems in order to compare baseline SCE frequencies.

DNA replication during differentiation of cortical cells in Allium roots

In the elongation zone of Allium roots a certain fraction of cortical cells undergo DNA replication during transition from newborn non-proliferative cells to mature cells. The percentage of cortical cells in the mature zone with DNA content 2C (G01) and 4C (G02) is roughly 60% and 40%, respectively. We propose that a replication signal whose concentration decreases the farther you go from the root tip, along the root axis, and which acts on cells after their last partitioning, could account for the observed distribution of mature cortical nuclei with different DNA contents.

[Early neonatal pneumococcal infections (author's transl)]

Five newborn infants with early pneumococcal infection are presented, two of them died. Until 1978 no cases of this infection were found in our Nursery. In the last three years pneumococcal septicemia has been responsible for nine percent of early neonatal infections. The clinical findings are identical to those seen in type-B beta hemolytic infections. The maternal genital tract colonization maight fetal colonization.

The birth and growth of neuroradiology in the USA

Neuroradiology in the USA was started by the neurosurgeon Harvey Cushing, who personally made the first X-rays used to treat a patient with a neurological disability, and Walter Dandy, who first performed air ventriculography, ventriculoscopy, air encephalography and air myelography. The father of neuroradiology in the USA was Merrill Sosman, Cushing's associate. Modern neuroradiology was introduced into the USA from Europe by Mannie Schechter who was one of the original team of three Chief Editors of Neuroradiology.

Antibody-independent complement activation by a subpopulation of mitogen-induced human T lymphoblasts

A study was made of the complement activation (CA) capacity of human T lymphoblasts obtained in vitro by PHA stimulation of highly purified T cells. The CA was studied by immunofluorescent detection of the C3 fragments deposited onto the cell membrane following incubation in autologous normal human serum (NHS). Whereas resting T cells did not stain, a mean of 12% of the blast cells were positive for monospecific anti-human C3 fluorescent serum. The possible mechanism through which C3 was deposited on the cell membrane may be a consequence of CA, because complement membrane fluorescence (CMF) was abolished by chelation of divalent cations with EDTA, complement inactivation by heating or incubation at low temperature. This reaction appears to occur in the absence of antibodies, because similar results were found when human agammaglobulinaemic serum was used as the complement source. The addition of ethyleneglycolbis-(aminoethylether)-tetraacetate (EGTA), supplemented with MgCl2 to the NHS failed to abolish the fluorescence, indicating that the alternative pathway was involved in the phenomenon. It is likely that the capacity to activate complement may distinguish a functional subpopulation of human T lymphoblasts.

ON THE NATURE OF SISTER-CHROMATID EXCHANGES IN 5-BROMODEOXYURIDINE-SUBSTITUTED CHROMOSOMES

Sister-chromatid exchanges (SCE) were studied in Allium cepa L. meristematic cells at the second and third divisions after BrdUrd-substitution during just the first or during the second and third cycles, respectively. The observed SCE nonreciprocal/reciprocal ratios detected at the third division in both experiments, as well as comparison of the lowest SCE frequency observed per cycle and expressed per picogram of DNA with data from different species expressed accordingly, strongly suggest that most of the exchanges detected in BrdUrd-substituted chromosomes are BrdUrd-dependent events. Hypotheses suggesting some different mechanisms are discussed to explain the formation of these BrdUrd-dependent SCEs.

Antibody-independent activation of complement by human peripheral B lymphocytes

Normal human peripheral blood lymphocytes were shown to activate complement in normal human serum (NHS). This activation led to C3 fixation on the cell membrane, which in turn was visualized by fluorescence. The reaction occurred in the absence of detectable amounts of antibodies, since an agammaglobulinemic patient's serum also supported complement activation, and the results were unaltered by absorption of normal human serum. Trypsin treatment of lymphocytes to remove possible complement activators bound to the cell membrane, did not have any effect on the complement activation by lymphocytes. Complement membrane fluorescence was abolished in the presence of EDTA or ethyleneglycolbis(aminoethylether) tetraacetate (EGTA) supplemented by Mg++ions indicating that the classical pathway of complement activation was involved in the reaction. Experiments performed with T and B-purified populations showed that the phenomenon was confined to the B cell fraction. Complement deposition did not diminish the number of EAC rosettes, and viability remained unchanged after exposure of lymphocytes to normal human serum.

[Hemodynamic changes in hypoglycemic shock]

Severe hypoglycemia may be present in seriously ill patients; if it is not corrected opportunely a series of neuroendocrinal mechanisms take place aimed at correcting metabolic alterations. These mechanisms can produce hemodynamic alterations as well. Nine mongrel dogs were studied with continuous registration of: blood pressure, central venous pressure, cardiac frequency, respiratory frequency, electrocardiogram and first derivative (Dp/Dt). Six dogs received crystalline (fast acting) insuline intravenously (group 1). After hemodynamic changes were registered hypoglycemia was corrected with 50 per cent glucose solution. Complementary insuline doses were administered to three dogs (group 2); in this group hypoglycemia was not corrected. In group 1 during hypoglycemia there was an increase in blood pressure, central venous pressure, cardiac frequency, respiratory frequency and Dp/Dt, and changes in QT and T wave on the EKG; these changes were partially reversible after hypoglycemia was corrected. The above mentioned alterations persisted in group 2, breathing became irregular irregular and respiratory arrest supervened. It can be inferred that the hemodynamic response to hypoglycemia is predominantly adrenergic. The role of catecolamines, glucocorticoides, glucagon, insuline, cyclic AMP in metabolic and hemodynamic alterations consecutive to hypoglycemia are discussed.

Method for simultaneous detection of proteinase and esterase activities in extremely halophilic bacteria

A method was developed for simultaneous detection of proteinase and esterase activity in extremely halophilic bacteria by combining Tween hydrolysis and gelatin hydrolysis on a single plate.