Computer visual syndrome in university students in times of pandemic.

INTRODUCTION: One of the consequences of prolonged use of bright screens such as those of the computer or cell phone, is the computer visual syndrome where characteristic symptoms are presented that normally disappear after a couple of hours when you stop using electronic devices. The prevalence is high due to multiple risk factors. OBJECTIVE: To determine the prevalence of computer vision syndrome in medical students at the University of Boyacá in times of pandemic. METHODOLOGY: Descriptive and cross-sectional observational study. The study population were medical students, the data were collected in September and October of the year, an electronic survey was carried out for data collection. RESULTS: A total of 300 participants were invited to participate in the study. 78% (234) of participating students suffer from SVI. 67.09% (157) of the participants who reported suffering from SVI were female and 32.91% (77) were male. CONCLUSIONS: Computer visual syndrome is very common among medical students at the University of Boyacá. This study has shown that the presence of SVI has been significantly associated with exposure factors that were triggered during the pandemic period, where frequent virtual classes and long hours led to high exposure to screens. In addition, in the era of virtuality, communication through social networks increased the use of cell phones, which increases the possibility of the appearance of this syndrome.

Cooperation of lysosomes and inner mitochondrial membrane in the degradation of carbamoyl phosphate synthetase and other proteins.

Carbamoyl phosphate synthetase (CPS) from rat liver is proteolitically inactivated at acid pH by broken lysosomes. Inactivation increases when lysosomes are previously incubated with inner mitochondrial membrane, although this mitochondrial fraction does not inactivate CPS 'per se'. The increased degradation is due to membrane factor(s), most probably mitochondrial proteinase(s), solubilized by lysosomal matrix proteinases, after incubation of the inner mitochondrial membrane fraction with broken lysosomes. This (these ) factor(s) degrade(s) CPS and other proteins in the absence of lysosomal proteinases or when these are inhibited by leupeptin, chymostatin and pepstatin. We have also tested the possible regulation of this degradation and found that ATP and, particularly, acetyl glutamate accelerate the degradation of CPS by the factor(s) liberated from the inner mitochondrial membrane.

Differences in the half-lives of some mitochondrial rat liver enzymes may derive partially from hepatocyte heterogeneity.

The different turnover rates of rat liver mitochondrial enzymes make autophagy unlikely to be the main mechanism for degradation of mitochondria. Although alternatives have been presented, hepatocyte heterogeneity has not been considered. Lighter hepatocytes isolated in a discontinuous Percoll gradient contain more glutamate dehydrogenase (GDH) (half-life 1 day) and a more active autophagic system than heavier hepatocytes. The latter contain more carbamoyl phosphate synthase (CPS) and ornithine carbamoyl transferase (OTC) (half-lives 8 days) but less lysosomal activity. As expected, isolated autophagic vacuoles contain, relative to the mitochondrial content, 3-times less OTC and CPS than GDH, probably reflecting a faster lysosomal engulfment of mitochondria in the light hepatocytes (which contain more GDH). These data may explain some of the half-life differences of the enzymes studied.

The mitochondrial probe rhodamine 123 inhibits in isolated hepatocytes the degradation of short-lived proteins.

The fluorescent dye rhodamine 123 (R123) decreases the intracellular ATP levels and also inhibits the degradation of short-lived proteins in isolated hepatocytes. This inhibition affects lysosomal and, to some extent, non-lysosomal mechanisms. The degradation of short-lived proteins decreases more when ATP levels are less than 40% of those in control cells, in contrast to the reported linear correlation between ATP levels and degradation of long-lived proteins. R123 provides a powerful probe for clarifying the proteolytic mechanisms involved in degradation of short-lived proteins and the ATP requirements in protein degradation. Indeed, as illustrated, the results suggest different mechanisms for the degradation of short- and long-lived proteins. Moreover, they provide a warning for the clinical use of this reagent.

[Unusual variant of laryngeal squamous cell carcinoma: verrucous carcinoma]. / Variante inusual de carcinoma escamoso laríngeo: carcinoma verrucoso.

Verrucous carcinoma is an uncommon but distinctive variety of squamous cell carcinoma, accounting for 1 to 2% of all laryngeal neoplasms. It was first described as a distinct clinicopathological entity by Ackerman in 1948. It has been described most frequently in oral cavity and larynx, but other sites are possible. The preferred location of verrucous carcinoma of the larynx is supraglottic. Its general similarity with papillomas and other papillomavirus-induced lesions has raised the question of a viral etiology (human papillomavirus); HPV-16-related DNA sequences have been found in some verrucous carcinomas using a DNA hybridization technique. We report two cases of verrucous carcinoma and discuss some interesting particularities of these tumors: origin, clinical features, pathology and prognosis.

Endocytosis of liposomes containing lysosomal proteins increases intracellular protein degradation in growing L-132 cells.

We have used a new approach to test the possible participation of lysosomes in the degradation of long-lived proteins. Rat liver lysosomal proteins were introduced, via multilamellar liposomes, into L-132 cells. Viability and protein synthesis were not impaired by this treatment. The liposomal content was released into the lysosomes of the cultured cells, as revealed by ferritin uptake and electron microscopy. Degradation rates of long-lived proteins increased with the uptake of lysosomal proteases. However, the increased protein degradation of chloroquine and leupeptin, in contrast to the inhibition by these reagents of the increased protein degradation of cells 'starved' of serum (step-down conditions). This approach opens a new way of investigating the degradation of intracellular proteins in cultured cells.

Vanadate inhibits degradation of short-lived, but not of long-lived, proteins in L-132 human cells.

Vanadate, at concentrations higher than 0.04 mM, inhibits the intracellular degradation of short-lived proteins in exponentially growing L-132 human cells. The inhibition is not due to a decrease in viability or in the ATP contents of the cells. Since vanadate decreases proteolysis in cell extracts, the inhibition appears to affect the proteinases which degrade these proteins. Under optimal nutritional conditions, the degradation of long-lived proteins is accelerated by vanadate, thus providing additional evidence that in exponentially growing cultured cells degradation of short- and long-lived proteins occurs by different processes. Vanadate also efficiently inhibits the lysosomal degradation of endocytosed proteins and of long-lived proteins under step-down conditions. However, this effect seems to be unrelated to the observed inhibition of degradation of short-lived proteins, because chloroquine and leupeptin, which inhibit degradation of proteins by lysosomes, do not modify the degradation of these proteins. Our results provide for the first time a probe which, owing to its opposite effects on the degradation of short- and long-lived proteins, could be useful to clarify the mechanisms involved in protein degradation in cultured cells.

Analysis by flow cytometry of rat hepatocytes from different acinar zones.

Many functional, morphological and biochemical differences among hepatocytes from different acinar zones have been described. Therefore, it will facilitate studies on liver metabolism rapid, non-destructive procedures to isolate hepatocytes from these zones. Flow cytometry is a new powerful tool which, however, has not been used thus far to accomplish the separation of hepatocytes from different acinar zones. We describe here various cytometric parameters which characterize hepatocyte populations, separated by isopycnic centrifugation in Percoll gradients. The intraacinar origin of the different hepatocytes was assessed by enzymatic and morphological measurements.

Flow cytometric analysis of the effects of high protein diet on isolated rat liver mitochondria.

We have investigated changes that occur in mitochondria obtained from the livers of rats that had been maintained on a high protein diet (80% casein instead of 20%) for 6 months. Liver homogenates were separated by centrifugation into a mitochondrial fraction, a nuclear fraction and the supernatant fluid of the nuclear fraction (nuclear wash). Rhodamine-123 was used to selectively stain mitochondria depending upon their membrane potential. The stained organelles were processed through a flow cytometer where the fluorescent stains were excited by the 488 nm wavelength of a laser and the resultant fluorescence signals analysed. After 6 months on a high protein diet, mitochondria displayed an increase in the fluorescence associated with rhodamine-123 uptake in both mitochondrial and nuclear wash fractions, while mitochondrial fluorescence in the nuclear fraction showed a heterogeneous distribution. This was interpreted as an increase in membrane potential in most of the liver mitochondria under these nutritional conditions, with a certain degree of heterogeneity. These functional changes may be correlated with morphological alterations previously reported and show the usefulness of flow cytometry for biochemical analysis of isolated mitochondria.

Regulatory mechanisms of intracellular proteolysis in mammalian cells.

Low molecular weight phosphoryl compounds, such as carbamoyl phosphate, 2,3-diphosphoglycerate and phytic acid protect, to different extents, mitochondrial and cytosolic proteins such as ornithine transcarbamoylase (OTC), carbamoyl phosphate synthetase (CPS), glutamate dehydrogenase (GDH) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH), from proteolytic inactivation (rat liver lysosomal extracts, pronase, elastase). Given the wide variety and common occurrence of low molecular weight reagents such as typified here, it seems that this kind of inhibition may be important in the regulation of protein turnover. Regulation of intracellular proteolysis can also occur via the proteolytic systems. Immunocytochemical procedures for mitochondrial enzymes (CPS, GDH, OTC), show intracellular homogeneity, but intercellular heterogeneity in rat liver, compatible with a role of the autophagic-lysosomal system in degrading these proteins. However, degradation of short-lived proteins occurs by other mechanisms. Using centrifugation of cultured cells, we find that the Golgi apparatus takes part in the degradation of these proteins, probably by controlling the traffic of proteins or proteases to the degradation site.

Effects of centrifugation on the degradation of short-lived proteins in exponentially growing cultured cells.

The degradation mechanisms of short-lived proteins in cultured cells are unknown, probably due to the lack of procedures which specifically affect the degradation of these proteins. We found that centrifugation of cultured cells, growing either in monolayer or in suspension, between 5000 and 25,000g for 30 min, inhibits (more than 50%) the degradation of short-lived proteins but not of long-lived proteins. Protein synthesis or cell viability is not affected. Centrifugation also disorganizes the Golgi apparatus, as checked by routine electron microscopy, and inhibits the degradation of endocytosed proteins (a lysosomal process which is controlled by the Golgi apparatus). Using different centrifugation speeds, a good correlation was found between alteration of the Golgi apparatus and inhibition of protein degradation.

Use of rhodamine 123 to investigate alterations in mitochondrial activity in isolated mouse liver mitochondria.

The fluorescent dye Rhodamine-123, which selectively stains mitochondria depending on the mitochondrial membrane potential, was used with flow cytometry to evaluate alterations in activity of mitochondria isolated from mouse liver. Under in vitro conditions, with succinate and ADP present in the buffer, mitochondrial activity was affected by a variety of metabolic inhibitors that modify membrane potential. These results demonstrate clearly that flow cytometric techniques using Rhodamine-123 can be employed to study activity in isolated mitochondria.

[Study of the heart conduction system in atrioventricular disorders]. / El estudio del sistema de conducción en las discordancias auriculoventriculares.

A His electrogram was registered with a Castillo tripolar catheter in seven patients with atrio-ventricular discordance and transposition of the great arteries (corrected transposition). They all had ventricular septal defect, six had pulmonary stenosis. two had atrial septal defect, and only one patient presented first degree AV block. The QRS was of normal duration, 4 had RBBB morphology in the left precordials. Two with ASD and VSD had a prolonged P/A interval. In one, the His recording was polyphasic with a prolonged H-V (55 msec) and two others showed a wide polyphasic His potential (25 and 26msec), with a prolonged H-V. These 3 cases with prolonged His had a minor degree of RBBB. The remaining 3 showed normal AV conduction. In all, the Purkinje electrogram was registered. The duration of the Pu potential and the Pu-V were normal. Corrected transposition shows a high incidence of slow AV conduction, frequently not detectable in the usual electrocardiogram in agreement with previous anatomo-pathological studies. The distal block would explain the frequency of complete AV block with low cardiac output and frequent sudden death in this type of heart disease. The distal block would compel us to take e more agressive steps in its treatment. Atrial septal defect with slowing of the intra-arial conduction is not detected in the electrocardiogram.

The effect of changing the mode of ventilation on the arterial-to-end-tidal CO2 difference and physiological dead space in laterally and dorsally recumbent horses during halothane anesthesia.

OBJECTIVE: To evaluate the effect of changing the mode of ventilation from spontaneous to controlled on the arterial-to-end-tidal CO2 difference [P(a-ET)CO2] and physiological dead space (VD(phys)/VT) in laterally and dorsally recumbent halothane-anesthetized horses. STUDY DESIGN; Prospective, experimental, nonrandomized trial. ANIMALS: Seven mixed breed adult horses (1 male and 6 female) weighing 320 +/- 11 kg. METHODS: Horses were anesthetized in 2 positions-right lateral and dorsal recumbency-with a minimum interval of 1 month. Anesthesia was maintained with halothane in oxygen for 180 minutes. Spontaneous ventilation (SV) was used for 90 minutes followed by 90 minutes of controlled ventilation (CV). The same ventilator settings were used for both laterally and dorsally recumbent horses. Arterial blood gas analysis was performed every 30 minutes during anesthesia. End-tidal CO2 (PETCO2) was measured continuously. P(a-ET)CO2 and VD(phys)NT were calculated. Statistical analysis included analysis of variance for repeated measures over time, followed by Student-Newman-Keuls test. Comparison between groups was performed using a paired t test; P < .05 was considered significant. RESULTS: P(a-ET)CO2 and VD(phys)/VT increased during SV, whereas CV reduced these variables. The variables did not change significantly throughout mechanical ventilation in either group. Dorsally recumbent horses showed greater P(a-ET)CO2 and VD(phys)/VT values throughout. PaCO2 was greater during CV in dorsally positioned horses. CONCLUSIONS AND CLINICAL RELEVANCE: Changing the mode of ventilation from spontaneous to controlled was effective in reducing P(a-ET)CO2 and physiological dead space in both laterally and dorsally recumbent halothane-anesthetized horses. Dorsal recumbency resulted in greater impairment of effective ventilation. Capnometry has a limited value for accurate estimation of PaCO2 in anesthetized horses, although it may be used to evaluate pulmonary function when paired with arterial blood gas analysis.