Baltazar Barrera-Mera

Release of classical transmitters and nitric oxide in the rat olfactory bulb, evoked by vaginocervical stimulation and potassium, varies with the oestrus cycle.

In vivo microdialysis was used to investigate the effects of ovariectomy and the oestrus cycle on vaginocervical stimulation‐evoked classical transmitter and nitric oxide release in the olfactory bulb of anaesthetized (urethane) and conscious rats. During pro‐oestrus/oestrus, vaginocervical stimulation (1 or 10 min) significantly increased concentrations of glutamate, aspartate, GABA, noradrenaline, dopamine and nitric oxide (citrulline) but failed to do so in met‐oestrus/di‐oestrus or following ovariectomy. Potassium chloride‐evoked GABA, noradrenaline and nitric oxide release in the olfactory bulb was also significantly enhanced during pro‐oestrus/oestrus. The effects of vaginocervical stimulation on olfactory bulb transmitter release during pro‐oestrus/oestrus were significantly reduced by pelvic or vagus nerve section. Basal concentrations of classical transmitters and nitric oxide in the olfactory bulb did not vary across the oestrus cycle although noradrenaline and dopamine levels were reduced following ovariectomy. These results confirm our previous electrophysiological data showing that the olfactory bulb mitral cells are only excited by vaginocervical stimulation during pro‐oestrus/oestrus. They also suggest that sex hormones acting primarily at the level of the olfactory bulb dramatically enhance the ability of vaginocervical stimulation to evoke release of both classical transmitters and nitric oxide in this region. Such alterations in neurochemical release in the olfactory bulb may be important for mediating plasticity changes underlying olfactory recognition of mates or offspring.

Neural coupling between left and right electroretinographic circadian oscillations in the crayfish p. bouvieri

Abstract 1. 1. The effects of light pulse and surgical bisections of the cerebral ganglion upon the coupling of electroretinographic (ERG) circadian rhythm of left and right eyestalks were examined in the crayfish Procambarus bouvieri (Ortmann). 2. 2. The results indicate that the application of light for 60 min (0.15 cd/ft2) at only one of the eyestalks induces a short-lasting bilateral decrease in the ERG voltage and a simultaneous phase shift in both left and right ERG rhythms in the following oscillations. 3. 3. The relatively long-lasting latency of ERG depression heterolaterally induced (15–25 min) as well as its recovery time (10–20 min) suggest that this contralateral modulation would be of neuroendocrine nature. 4. 4. Four patterns of ERG rhythms were recorded after cerebral ganglion bisection: (1) ERG damped oscillations, (2) bilateral or (3) unilateral ERG rhythms, and (4) lack of ERG oscillations. 5. 5. The above-mentioned changes suggest an important coupling mechanism between both eyestalks, with the result that ERG circadian pacemakers are mutually synchronized.

The cartesian clock metaphor for pineal gland operation pervades the origin of modern chronobiology

In theoretical descriptions formulated during the 1600s, R. Descartes attributed a clock-like role to the pineal gland. He established the belief that pineal function underlies the laws of the universe that determine the cyclic sleep-awake states in man. Recent reports about pineal circadian pacemakers now validate the brilliant accuracy of Cartesian thought, in relation to the relevant role of the pineal gland.

Circadian Locomotor Activity Under Artificial Light in the Freshwater Crab Pseudothelphusa americana

Long-term recordings of locomotor activity were obtained from intact freshwater crabs, Pseudothelphusa americana in constant darkness (DD), constant light (LL) and different light-dark (LD) protocols. Bimodal rhythms were typically observed in this crab when subjected to DD or LD, with bouts of activity anticipating lights-on and lights-off, respectively. Freerunning circadian rhythms were expressed in both DD and LL for longer than 30 days. In DD, we observed that some animals presented different period lengths for each activity component. During LL, activity was primarily unimodal, however spontaneous splitting of the rhythms were observed in some animals. When activity was recorded under artificial long days, the morning bouts maintained their phase relationship but the evening bouts changed their phase relationship with the Zeitgeber. Our results indicate that, bimodal locomotor activity rhythm in the crab Pseudothelphusa americana is variable among organisms. The characteristics of phase relationship with LD and responses to LL for morning and evening bouts, suggest that, locomotor activity could be driven by multiple oscillators, and that coupling between these oscillators may be regulated by light.

Circadian Locomotor Activity Rhythm in the Freshwater Crab Pseudothelphusa americana (De Saussure, 1857): Effect of Eyestalk Ablation

The circadian rhythm of locomotor activity in the freshwater crab, Pseudothelphusa americana, was studied in aquaria using infrared crossing sensors. Individuals with ablated eyestalks were compared with intact individuals in constant darkness (DD) and in light-dark cycles (LD). Our results showed that intact animals in DD displayed bimodal rhythms. In LD conditions the two peaks were associated with lights on and lights off, respectively. A significant difference in the free running periods before and after LD was observed in all intact animals. After eyestalk ablation (ES-X), the circadian rhythm of locomotor activity disappeared immediately, but reappeared several days later. Diurnal activity was seen in some ES-X animals when exposed to LD. Our results indicate that locomotor activity rhythm in P. americana is driven primarily by oscillators located outside the eyestalks, and that extraretinal photoreceptors mediate either entrainment or masking effects.

Electrophysiological evidences of mutual modulatory influences on the retinal activity of the crayfish Procambarus bouvieri (O)

Electroretinographic evoked potentials (ERGs) were recorded in dark adapted crayfish by the application of pulses of light (0.09 Cd/ft2) presented every 2.5 min. Heterolateral illumination (HI) for sixty min (0.06-0.3 Cd/ft2) induced up to 50% decrease in ERG after a latency of 12-25 min. ERG depression was proportional to the intensity of HI and also showed a circadian rhythm. During the alpha phase the ERG recovery started 3-10 min after HI was turned off. In contrast it started only after 10-20 min during the rho phase. The time course of the ERG depression, which was abolished in splitbrain animals, strongly suggests that a mutual modulatory influence, probably of neuroendocrine nature, is present in the crayfish visual system.

Hepatic Metastasis from Colorectal Cancer

The liver is the most common site of metastasis in patients with colorectal cancer due to its anatomical situation regarding its portal circulation. About 14 to 18% of patients with colorectal cancer present metastasis at the first medical consultation, and 10 to 25% at the time of the resection of the primary colorectal cancer. The incidence is higher (35%) when a computed tomography (CT) scan is used. In the last decades, a significant increase in the life expectancy of patients with colorectal cancer has been achieved with different diagnostic and treatment programs. Despite these improvements, the presence of metastasis, disease recurrence, and advanced local tumors continue to remain poor prognostic factors. Median survival without treatment is <8 months from the moment of its presentation, and a survival rate at 5 years of 11% is the best prognosis for those who present with local metastasis. Even in patients with limited metastatic disease, 5-year survival is exceptional. Patients with hepatic metastasis of colorectal cancer have a median survival of 5 to 20 months with no treatment. Approximately 20 to 30% of patients with colorectal metastasis have disease confined to the liver, and this can be managed with surgery. Modern surgical strategies at the main hepatobiliary centers have proved that hepatectomy of 70% of the liver can be performed, with a mortality rate of <5%. It is very important to have knowledge of predisposing factors, diagnostic methods, and treatment of hepatic metastasis. However, the establishment of newer, efficient, preventive screening programs for early diagnosis and adequate treatment is vital. How to cite this article: Valderrama-Treviño AI, Barrera-Mera B, Ceballos-Villalva JC, Montalvo-Javé EE. Hepatic Metastasis from Colorectal Cancer. Euroasian J Hepato-Gastroenterol 2017;7(2):166-175.

Visual circadian rhythmicity in splitbrain crayfish: A plastic behavioral expression of symmetric circadian pacemakers

Electroretinographic evoked potentials (ERGs) were continuously recorded in dark-adapted, splitbrain crayfishes Procambarus bouvieri. Pulses of light (0.95 cd/m2) illuminating the left or the right eyes were alternatively applied every 15 or 30 min. As compared to intact crayfish, uni or bilateral damping or suppression of circadian retinal sensitivity rhythm could be caused by surgical bisection of cerebral ganglion in these crustaceans. The damped ERG circadian rhythm was rapidly reversed by reduction or elimination of the test light stimulus to the contralateral eye. Given the redundant processing of pacemaking information coming from bilaterally positioned cephalic circadian pacemakers to the central nervous system in splitbrain crayfish, photodependent damping of ERG rhythm revealed a plastic potential of central circadian pacemakers. The possibility that a strong but reversible inhibitory influence acts simultaneously upon the left and right protocerebral circadian pacemakers while receiving bilateral photic stimulation is considered.

Affordable laparoscopic simulator to acquire basic skills in undergraduate surgery students

The laparoscopic surgery has proved to be the main approach for a number of pathologies that require surgical intervention. This due to its lower incidence of complications, to a faster recovery time compared to traditional open surgery and reduction of surgery time1. This has led to the need in training and acquisition of skills in minimally invasive surgery in early stages of the medical career of students inclined toward a surgical specialty. The complications during this learning process have resulted in ethical considerations, imposed by the medical profession, specifically in the use of humans and animals in the surgical training.2 This has led to the development of simulator devices to develop skills and training of surgeons. These aspects are not confined to the postgraduate students, study plans at the undergraduate level generate an imminent need to ABSTRACT

Circadian locomotor activity in the juvenile red eared turtle Trachemys scripta elegans: free running and entrainment

Long-term circadian locomotor activity under different light conditions and its corresponding free running periods were studied in the juvenile red-eared turtle Trachemys scripta elegans. Diurnal activity and a long free running period in darkness was observed in LD 12:12, skeleton photoperiod, and long and short days (LD 16:08, LD 08:16, respectively). Anticipation of activity to lights-on and length of activity phase depends on the photoperiod used. After-effects were observed in free running conditions after long day photoperiods. Constant light effect produces mainly the lack of circadian rhythm after a few days of period lengthening and the lack of rhythm may persist for a few days after re-entering constant darkness conditions. The results of the present report indicate that in T. scripta elegans, it is suitable to perform studies on circadian biology in juvenile turtles and its interaction with changes of photoperiod at constant temperature.