A simple procedure to obtain one-micrometer sections of routinely embedded paraffin material

By freezing blocks of paraffin-embedded tissues to a convenient temperature it is possible to obtain routinely 1 micron sections that can be further processed as normal thicker sections. Normal and disposable steel knives can be used and the staining time should be increased in most procedures. Gradual freezing of blocks to the temperature of dry ice is the simplest and safest way to obtain an adequate temperature. The best results were obtained using as fixative 4% paraformaldehyde in phosphate buffered saline solution.     

Effects of 6-hydroxydopamine and 5-hydroxydopamine onlthe teleost melanophores innervation

Intraperitoneal injections of 6-OH-dopamine (80 mg kg^−l) promote, in toad fish, killifish, lsummer and winter flounders, a darkening of their colour and loss of capacity to adapt tolthe colour of the background. This condition persisted for three weeks after which thelanimals gradually returned to normal. The study of the skin of 6-hydroxydopamineltreated killifish showed degenerative lesions in the fine nerves and synapses of its melanophores, 124 h after the administration of the drug. These lesions progressed and 4 days later, lno synaptic structures could be detected in these cells. This condition persisted up to thel20th day. These results suggest that melanophores have a single monoaminergic innervaion.     

Structure of the tail fin in teleosts

The influence of adrenalectomy and administration of hypertonic saline on the amount of vasopressin, oxytocin, and neurophysin contained in the median eminence and the neural lobe of rats was studied by means of the following methods: (i) morphometric and microphotometric analyses of aldehyde fuchsin-stained histological sections of the neurohypophysis; (ii) immunohistochemical demonstration of vasopressin, oxytocin, and neurophysin in the neurohypophysis, and (iii) radioimmunological measurement of vasopressin and oxytocin in extracts of the median eminence and the neural lobe. Adrenalectomy increases the amount of vasopressin and neurophysin in the external layer of the median eminence but does not change the content of oxytocin. It has no influence on the amount of vasopressin, oxytocin, and neurophysin demonstrable in the inner layer of the median eminence and in the neural lobe two weeks after the operation. Hypertonic saline markedly diminishes the vasopressin, oxytocin, and neurophysin content of the inner layer of the median eminence and the neural lobe but reduces only slightly, if at all, the amount of vasopressin and neurophysin in the outer layer of the median eminence. The findings support the concept that osmotic stress reduces only the vasopressin and oxytocin content of the hypothalamus-neural lobe system and has no or only little influence on the vasopressin content of the outer layer of the median eminence.     

PERFUSION FOR MYOCARDIAL REVASCULARIZATION WITHOUT AN ARTIFICIAL OXYGENATOR (New Method to Reduce Surgical Morbidity)

Thirteen patients were submitted to direct myocardial revascularization (saphenous vein graft) without the use of an artificial oxygenator. The perfusion was done by a left ventricle-to-aorta bypass and autogenous oxygenation. Most patients had three grafts implanted plus endarterectomy of the distal right coronary artery. There was one hospital death that was apparently not related to the method used. Perfusion time ranged from 45 minutes to 4 hours. Body temperature during perfusion was kept between 25 and 30 degrees C. Perfusion flow was maintained between 25 to 50 ml per kg of body weight per minute. Ischemic, hypothermic cardiac arrest was employed. We demonstrated for the first time that perfusion for this kind of heart surgery could be done with no artificial oxygenators and, apparently, is safer for the patients. There were no bleeding problems even in perfusions as long as 4 hours. There was no respiratory dysfunction, and artificial respiration was used for only 6 to 12 hours. The patients awoke at the end of surgery with no signs or symptoms of central nervous system damage, and vasopressor drugs were rarely used after surgery. Although the experience is very small, it suggests that many postoperative problems, especially those related to bleeding and respiratory dysfunction may be reduced or eliminated by this new method.     

Effect of menthol in experimentally induced ulcers: Pathways of gastroprotection

Based on ethnopharmacological indications that Mentha species may be used in the treatment of gastrointestinal diseases, this study aimed to characterize the gastroprotective mechanisms of menthol (ME), the major compound of the essential oil from species of the genus Mentha. The gastroprotective action of ME was analyzed in gastric ulcers that were induced by ethanol or indomethacin in Wistar male rats. The mechanisms responsible for the gastroprotective effect were assessed by analyzing the amount of mucus secreted, involvement of non-protein sulfhydryl (NP-SH) compounds, involvement of calcium ion channels and NO/cGMP/K⁺_ATP pathway, gastric antisecretory activity and the prostaglandin E₂ (PGE₂) production. The anti-diarrheal activity and acute toxicity of ME were also evaluated. Oral treatment with ME (50 mg/kg) offered 88.62% and 72.62% of gastroprotection against ethanol and indomethacin, respectively. There was an increased amount of mucus and PGE₂ production. The gastroprotective activity of ME involved NP-SH compounds and the stimulation of K⁺_ATP channels, but not the activation of calcium ion channels or the production of NO. The oral administration of ME induced an antisecretory effect as it decreased the H⁺ concentration in gastric juice. ME displayed anti-diarrheal and antiperistaltic activity. There were no signs of toxicity in the biochemical analyses performed in the rats’ serum. These results demonstrated that ME provides gastroprotective and anti-diarrheal activities with no toxicity in rats.     

Genetic strategies for improving hyaluronic acid production in recombinant bacterial culture

Hyaluronic acid (HA) is a biopolymer of repeating units of glucuronic acid and N-acetylglucosamine. Its market was valued at USD 8.9 billion in 2019. Traditionally, HA has been obtained from rooster comb-like animal tissues and fermentative cultures of attenuated pathogenic streptococci. Various attempts have been made to engineer a safe micro-organism for HA synthesis; however, the HA titres obtained from these attempts are in general still lower than those achieved by natural, pathogenic producers. In this scenario, ways to increase HA molecule length and titres in already constructed strains are gaining attention in the last years, but no recent publication has reviewed the main genetic strategies applied to improve HA production on heterologous hosts. In light of that, we hereby compile the advances made in the engineering of micro-organisms to improve HA synthesis.     

Chronic fenfluramine treatment of rats with different ages: Effects on brain oxidative stress-related parameters

Fenfluramine is an anorectic drug widely used for the regulation of food intake that presents some adverse effects at the central and peripheral levels. d-Fenfluramine, an isomer of dl-fenfluramine, is postulated to be more effective and to induce less side effects than the racemic compound. These drugs act preferentially on the serotonergic system. Some authors have suggested that fenfluramine causes a degeneration of serotonergic neurons. Alterations of the serotonergic system are also observed during the aging process, and in this case, a relationship with reactive oxygen species has been already established. In view of these data, the present study was conducted to investigate the relationship between fenfluramine and brain antioxidant defense system in mature and aged animals. Rats aged 4 and 17 months were chronically treated with dl-fenfluramine, d-fenfluramine, or saline. Brain activity of superoxide dismutase and glutathione peroxidase was significantly affected by aging. Catalase activity was altered by the treatment. Total glutathione content and chemiluminescence in the brains were also altered by aging. Glutathione levels were altered as a function of the interaction between age and treatment. These findings suggest that treatment with d- or dl-fenfluramine results in alteration of the antioxidant system that could be exacerbated when associated with the aging process. © 1997 John Wiley & Sons, Inc.     

Activation of class III ribonucleotide reductase from E. coli. The electron transfer from the iron-sulfur center to S-adenosylmethionine

The anaerobic ribonucleotide reductase (ARR) from E. coli is the prototype for enzymes that use the combination of S-adenosylmethionine (AdoMet) and an iron-sulfur center for generating catalytically essential free radicals. ARR is a homodimeric alpha2 protein which acquires a glycyl radical during anaerobic incubation with a [4Fe-4S]-containing activating enzyme (beta) and AdoMet under reducing conditions. Here we show that the EPR-active S = 1/2 reduced [4Fe-4S]+ cluster is competent for AdoMet reductive cleavage, yielding 1 equiv of methionine and almost 1 equiv of glycyl radical. These data support the proposal that the glycyl radical results from a one-electron oxidation of the reduced cluster by AdoMet. Reduced protein beta alone is also able to reduce AdoMet but only in the presence of DTT. However, in that case, 2 equiv of methionine per reduced cluster was formed. This unusual stoichiometry and combined EPR and M?ssbauer spectroscopic analysis are used to tentatively propose that AdoMet reductive cleavage proceeds by an alternative mechanism involving catalytically active [3Fe-4S] intermediate clusters.     

Effect of DHEA Glutamate Release from Synaptosomes of Rats at Different Ages

Dehydroepiandrosterone (DHEA) exerts multiple effects in the central nervous system. Most of them seem to be mediated through their nongenomic actions on neurotransmitter receptors, and these actions occur within seconds or milliseconds. DHEA increases neuronal excitability, enhances neuronal plasticity, and has neuroprotective properties. By investigating glutamate release from synaptosomes of rats at different ages (from 17 days to 12 months), we observed that (i) there is an increase in basal and K(+)-stimulated L-[3H] glutamate release in rats at 12 months old, when compared to other ages; and (ii) there is an inhibitory effect of DHEA on basal L-[3H] glutamate release in 12 months old. This inhibitory effect of DHEA could be related to its reported protective role against excitotoxicity caused by overstimulation of the glutamatergic system and ageing.