Specific induction of uncoiling and recombination by azacytidine in classical satellite-containing constitutive heterochromatin

Azacytidine (ACR) is known to induce uncoiling and somatic association involving the constitutive heterochromatin of human chromosomes 1, 9, 15, and 16 and the Y. These regions are composed of alphoid and classical satellite DNA sequences. Using specific probes for chromosomes 1 and 16, we have performed two-color fluorescence in situ hybridization on human lymphocytes cultured in the presence of ACR. We demonstrate that for these two chromosomes (1) uncoiling and association specifically occur in classical satellite-containing regions at the first cell generation, (2) breakages also affect these regions, and (3) somatic recombinations occur between these regions and lead to translocations at the next cell generation. These results suggest that changes in methylation of repetitive DNA sequences are related to chromosomal instability occurring during cell transformation and tumorigenesis.

[Neuroradiology in the physiopathologic diagnosis of subarachnoid hemorrhage--cerebral aneurysm]

The clinical importance of the cerebral aneurismatic lesion in well known. In Portugal we still do not have reliable statistics regarding the occurrence of the subarachnoid hemorrhage, however we can make a comparison through Kassel's and Drake's studies where they refer that annually 28,000 North-Americans suffer from subarachnoid hemorrhage attributed to the rupture of the cerebral aneurysm. This is a clinical situation that needs to be analyzed, more so because if it is not diagnosed and treated in time, it can cause a high level of morbidity and mortality. From 1984 to 1990, the authors studied 208 clinical cases of in-patients at the Santa Maria Hospital who had been diagnosed as having subarachnoid hemorrhage-cerebral aneurysm. They analyzed 172 cranium-encephalic Tomographies and 190 cerebral Angiographies. They found levels that overlapped the series already published with respect to the location of the lesion, dimensions and age groups involved. They tried to relate the presence aneurysm in the willis arterial circle with the occurrence of locoregional anatomic variants that were detected in 51% of the patients with aneurysm of the anterior communicating artery and in 33% of the cases in the posterior communicating artery. The high occurrence of serious forms of tomodensitrometric presentation should also be emphasized. As a matter of fact, 42.6% of the patients studied were grouped in degree IV of the Fisher Scale. This result translates the effort that is still required towards an early clinical and imaging diagnosis of warning hemorrhage to avoid or prevent a catastrophic hemorrhage recurrence.

Ketogenesis from lactate in rat liver during the perinatal period

Lactate, which accumulates in neonatal plasma during the first hours after delivery, is used by neonatal tissues as a source of energy and carbon skeleton. In this work, lactate use by rat liver during late gestation (last 3 d) and early neonatal life (6 h postpartum) has been studied. The rate of lactate use by liver was compared with that found with oleate, inasmuch as fatty acids are the main substrates for the liver after the onset of lactation. The main fate of lactate in the liver during the perinatal period was ketone bodies, preferentially over CO2 and lipids. The rate of oxidation of lactate and its incorporation into lipids decreased during late gestation, but the rate of ketogenesis from lactate remained high during this period. After birth, the rate of lactate oxidation sharply increased, but lipogenesis decreased and ketogenesis was maintained. The rates of oleate oxidation and ketogenesis from oleate were two orders of magnitude lower than those from lactate. However, the rate of oleate incorporation into lipids was only 4-fold lower than that observed from lactate under the same circumstances. Our results suggest that lactate is a major substrate for the liver during the perinatal period because it is mainly incorporated into ketone bodies. This may target lactate carbons to different neonatal tissues.

[Intravascular therapy of giant cerebral aneurysm]

The endovascular therapy in cerebral aneurysms has met significant technical progress, specially related with new microcatheters and different types of detachable balloons. Reviewing seven cases of giant cerebral aneurysms treated by intra arterial approach, the authors present their results pointing out and discussing the different angiosurgical therapy that can actually be used.

Lon-dependent regulation of the DNA binding protein HU in Escherichia coli

HU, the major DNA binding protein of Escherichia coli, exists in solution as a heterodimer composed of two highly homologous subunits: HU1, encoded by hupB; HU2, encoded by hupA. The purification of the HU protein from hupA- or hupB- bacteria showed that the hupB mutant strains synthesize normal amounts of the HU2 subunit (which corresponds to 60% of the total HU present in wild-type cells). On the contrary, the amount of HU1 present in hupA mutant strains corresponds to only 6% of the total HU present in wild-type cells. We showed by fusions of the hupB and hupA promoters to the malPQ operon that the absence of one subunit has no major effect on the transcription rate of the gene encoding the other subunit. Analysis of the stability of the HU1 and HU2 subunits, using pulse-chase labeling experiments, showed that the HU1 subunit is degraded specifically in the absence of the HU2 subunit and, moreover, that this degradation is dependent on the presence of the Lon protease.

Post-exercise changes of the Q-Tc interval in coronary heart disease

A study was made of variations of the Q-Tc interval as a result of exercise on 40 subjects, all submitted to coronary-angiography. The exercise tests were carried out on an ergometric bicycle and the Q-T interval, corrected for heart rate according to Bazett's formula, was measured on the resting ECG before the start of the test, and on the ECG recorded immediately following the end of the exercise. Of the 40 subjects, 29 had coronary heart disease and 11 were considered normal or showed non-significant lesions. In these 11, except for one with left bundle branch block, the Q-Tc showed a shortening on the ECG following exercise. Of the patients with coronary heart disease with or without the presence of contractility disturbances, 20 showed a prolongation of the Q-Tc following exercise, and eight showed no change. The Q-Tc variations were 0.05 sec. +/- 0.03. Analyzing the data as a 2 X 2 contingency table, the value of the alpha 2 corrected for continuity is 30.4, which is highly significant. Our study thus revealed that Q-Tc variations with exercise have a value for the diagnosis of coronary heart disease in exercise tests.

The rate pressure product: fact of fallacy?

The product of heart rate and blood pressure, (HR x BP), index of the myocardial oxygen consumption, was evaluated on 37 individuals with ages of between 32 and 65 years; 24 had ischemic heart disease with a disease of 1, 2 or 3 vessels, and 13 had non-significant lesions of 1 vessel (less than 75%) or no coronary heart disease (CHD). From the HR x BP correlation with the study of the angiograms of the coronary arteries, we verified that there was no distinction between patients. with CHD with or without an ejection fraction less than 50% or, with or without disturbances of myocardial contractility, and normal individuals. Thus, we believe that in patients with CHD, an excessive increase in the oxygen requirements of the myocardium is not the sole pathogenic mechanism of ischemia.

Experimental Yersinia pestis infection in rodents after intragastric inoculation and ingestion of bacteria

To clarify the pathogenesis of oral plague infection, we studied the susceptibility of three species of rodents to intragastric inoculation of Yersinia pestis, described the pathology and progression of infection, and measured antibody responses to fraction IA antigen of Y. pestis. The 50% lethal doses of bacteria by intragastric inoculation for Mus musculus, Zygodontomys pixuna, and Rattus rattus were log10 = 6.32, 5.46, and 9.62, respectively, which were at least 1,000-fold higher than the values obtained by subcutaneous inoculation. M. musculus was shown to be susceptible to lethal infection also when bacteria were ingested in drinking water. Microscopic pathology was consistent with heavy systemic infection. Quantitative cultures of tissues at different times after intragastric inoculation revealed that infections of blood, liver, and spleen preceded infections of Peyer's patches and mesenteric lymph nodes. Stool cultures were negative. The strain of Y. pestis used for inoculation was killed when exposed to a buffered solution at pH less than or equal to 3. Antibody responses were observed in some of the surviving rodents after intragastric challenge. These results showed that Y. pestis was an effective oral pathogen that produced fatal systemic infections and self-limited infections with immunity but did not produce enteric pathology or lead to fecal excretion of bacteria.

A control and data processing instrument for kidney tubule research

A microprocess-based instrument has been designed to facilitate research on the electrical properties of isolated renal tubules. Because of the high correlation between the electrical and ionic properties of tubules, this research helps in understanding the mechanisms of reabsorption and secretion along the many functionally different segments of a renal tubule. By replacing manual methods of control, measurement, and calculation, this instrument expedites the experimental procedure and adds accuracy and flexibility not available in the previous arrangement. Based on operational directives entered by the user, the instrument controls the number, frequency, polarity, intensity, and duration of current pulses through the tubule preparation and records the steady-state voltages induced at either end of the tubule. Then, using a transmission line model, it calculates and displays tubule parameters for each current pulse. The diameter of the tubule, as calculated from the model equations, is of immediate interest to the investigator. How well this figure compares with the physical diameter is an indication of the integrity of the preparation and the validity of the other calculations.