Differences in thermotolerance induced by heat or sodium arsenite: correlation between redistribution of a 26-kDa protein and development of protein synthesis-independent thermotolerance in CHO cells

In previous studies, we have demonstrated the differences in thermotolerance induced by heat and sodium arsenite (Lee et al., Radiat. Res. 121, 295-303, 1990). In this study, we investigated whether a 26-kDa protein might play an important role in evincing these differences. Chinese hamster ovary (CHO) cells treated for either 1 h with 100 microM sodium arsenite (ARS) or 10 min at 45.5 degrees C became thermotolerant to a test heat treatment at 43 degrees C administered 6 or 12 h later, respectively. After the test heating at 43 degrees C for 1.5 h, the level of 26-kDa protein in the nucleus was decreased by 92% in nonthermotolerant cells, 78% in ARS-induced thermotolerant cells, and 3% in heat-induced thermotolerant cells. Inhibiting protein synthesis with cycloheximide (CHM, 10 micrograms/ml) after ARS treatment eliminated thermotolerance to 43 degrees C and delayed restoration of the 26-kDa protein in the nucleus. In contrast, CHM neither prevented the development of thermotolerance nor inhibited the restoration of the 26-kDa protein in heat-induced thermotolerant cells. However, when cells were exposed to cold (4 degrees C), immediately after initial heating, restoration of the 26-kDa protein and development of thermotolerance did not occur. These results demonstrate a good correlation between the restoration and/or the presence of this 26-kDa protein and the development of protein synthesis-independent thermotolerance.     

Progebiophilus bruscai (Isopoda:Bopyridae) parasitizing the shrimp Upogebia dawsoni (Thalassinoidea:Upogebiidae), in Baja California Sur, Mexico)]

Parasitism of the isopod Progebiophilus bruscai Salazar-Vallejo & Leija-Tristán over the common mud shrimp, Upogebia dawsoni Williams, was analysed in the Ensenada and Bahia de La Paz, Baja California Sur, Mexico. Mud-shrimps were collected in three similar sites that differ in grain size and in the anthropogenic organic matter enrichment. Four-hundred-nine mud-shrimps were collected; the largest abundance was registered in the organically enriched site, but they were significantly smaller and more heavily parasited than the animals from the site lacking such organic enrichment. The size of the parasite is clearly dependent on the size of the mud-shrimp. This is the first study of the upogebiid-bopyris relationship in Mexico.     

Technique for repeated collection of cerebrospinal fluid from cisterna magna of anesthetized strain 13 guinea pigs

To study biochemical changes in cerebrospinal fluid (CSF), we developed a reliable technique for repeated collection of CSF in anesthetized strain 13 guinea pigs. The animal's head was mounted in a stereotaxic instrument with ventral tilt at 30 degrees, and cisternal puncture was made with an L-shaped, 23-gauge needle through the shaved skin. Clear CSF was collected in a 1-ml syringe surrounded by crushed ice. Each collection procedure lasted for 3 min, and three consecutive collections produced about 0.2 ml of CSF. Sampling was repeated at 3-hr intervals. With intravenous saline infusion (10 ml/kg.hr), a total volume of 0.6-1.0 ml of CSF was collected over 6 to 12 hr. Animals maintained a mean blood pressure, heart rate, and minute volume, with few changes during CSF sampling for the entire collection.     

The effect of intracoronary injections of x-ray contrast media on cardiac rhythm and conductivity during different variations of myocardial blood supply]

A study of the correlation between electrophysiologic effects of intracoronary injections of radiopaque agents and anatomical features of blood supply of cardiac conduction was carried out in 60 patients with intact coronary arteries. Coronary angiography was performed in all the patients. Disorders in cardiac conduction and repolarization in the myocardium were observed in intracoronary injection of radiopaque agents, which was accompanied by the development of S-A bradycardia. A bradyarrhythmic reaction type depends on prevalence of the left or right coronary artery in the atrial blood supply and cardiac conduction. The bradyarrhythmic effect was more pronounced in injection of a radiopaque agent in the right artery than in the left one.     

Clomipramine actions on firing rate in septal nuclei of the rat are not related to anaesthesia (urethane).

An increased firing rate in lateral septal nuclei (LSN) appears in urethane-anesthetized rats after several acute drug and non-drug human antidepressant treatments. A still more pronounced increase in firing rate is produced in LSN after clomipramine (CMI) long-term treatment. In spite of urethane is a widely used anesthetic for single unit extracellular recordings, it modifies evoked potentials wave-form. Therefore, present study discards urethane interaction with CMI in LSN single unit extracellular recordings. CMI was acutely injected (1.25 mg/kg: IP) either to urethane-anesthetized, or non-anesthetized encephale-isolé rats. The CMI treated groups showed higher rates of firing in LSN regardless of the use of general anesthesia during recordings. Another group of urethane-anesthetized rats received intracerebroventricular (ICV) microinjections of CMI (100 micrograms/10 microliters/1 min). An amount of 42.8% of LSN-recorded neurons responded with a long-lasting increased firing rate. Results discard urethane and CMI interactions. Additionally, systemic actions of CMI on firing rate of LSN are reproduced by ICV/route microinjections.     

Are dead Triatoma infestans a competent vector of Trypanosoma cruzi?

After Triatoma infestans death, Trypanosoma cruzi survived several days, maintaining the ability to infect a vertebrate host. Dead bugs from an endemic area collected during an official spraying campaign showed mobile rectal trypanosomes up to 14 days after vector death. Two days after vector death 2,760 trypomastigotes were found alive in its rectal material. However, the number of mobile trypomastigotes decreased significantly from the 5th day after death. Laboratory proofs with third and fifth nymphal stage showed similar results. Living trypanosomes were found in their rectal material at 10 days in third stage and even at 30 days in fifth nymphal stage. The mean number of trypomastigotes had no changes up to 10 days in third nymphal stage and increased significantly from 1 to 10 days in the fifth stage. Conjunctival instillation as well as intraperitoneal inoculation to mice, of metacyclic forms from dead T. infestans produced infection in the vertebrate host. Present results show that human contact with dead vector is highly probable in summer and living and infective T. cruzi are available for transmission in the vector.     

The effects of in vivo administration of endotoxin on the functions and interaction of hepatocytes and Kupffer cells

It was the purpose of this study to determine the effects of the in vivo administration of endotoxin on certain in vitro hepatocyte and Kupffer cell functions. An Alzet osmotic pump that contained endotoxin (LPS, 2.5 mg/100g) was implanted into the peritoneal cavity of 300g guinea pigs and delivered the endotoxin over a period of four days. In vivo administration of LPS did not cause a change in the in vitro release of albumin by isolated hepatocytes. However, when hepatocytes were co-cultured with Kupffer cells there was a significant decrease in albumin release for both control and LPS-treated animals. There was no difference between control and LPS-treated animals in the release of C3 by hepatocytes. However, there was a significant increase over the control group in C3 release by Kupffer cells from LPS-treated animals. When hepatocytes and Kupffer cells were cultured together, their release of C3 was not additive. Kupffer cells from LPS-treated animals released significantly greater amounts of PGE2 than control animals when stimulated in vitro with LPS. Thus, these Kupffer cells appeared to be primed to respond to an in vitro challenge of LPS. Kupffer cells from LPS-treated animals had significantly depressed antibody dependent cellular cytotoxicity (ADCC). This endotoxin model is useful for determining the in vivo effects of endotoxin on cellular function and gives some indirect evidence for the detrimental effects of LPS on the immune system and host defense.     

The differences in 12-hydroxyeicosatetraenoic acid and thromboxane B2 release from guinea pig platelets.

Anti-12(S)-hydroxyeicosatetraenoic acid (12-HETE)-antibody and anti-thromboxane B2 (TXB2)-antibody were generated and applied to the radioimmunoassay. The detection limit for 12-HETE was 16 pg. The cross-reactivities of anti-12-HETE-antibody were 4.6% for 15-HETE, 0.18% for 5-HETE and below 0.15% for leukotrienes and prostaglandins (PGs). 12-HETE and TXB2 released from guinea pig platelets were measured by radioimmunoassay. Platelet activating factor (PAF) at 10(-9) M induced the aggregation of platelets, the releases of immunoreactive-12-HETE (1.8 +/- 1.2 ng/10(8) platelets, mean +/- S.D.) and immunoreactive-TXB2 (18.5 +/- 17.3 ng/10(8) platelets). Collagen at 1 microgram/ml also evoked platelet aggregation, the releases of immunoreactive-12-HETE (2.7 +/- 1.1 ng/10(8) platelets) and immunoreactive-TXB2 (11.8 +/- 4.6 ng/10(8) platelets). By the stimulation with these compounds, TXB2 was produced in a greater amount than 12-HETE from guinea pig platelets. Although 10(-7) M and 10(-6) M U46619, a TXA2 mimetic, caused platelet aggregation, arachidonic acid metabolites were not released. These data suggest the presence of different mechanisms of platelet activation depending on each stimulus.