Mechanism and dynamics of macroautophagy in murine exocrine pancreatic cells. A review of vinblastine-induced changes.

Autophagy is a major pathway of lysosomal degradation of cellular macromolecules. The paper summarizes the results obtained in the studies on macroautophagy using the exocrine pancreatic acinar cell as model system and vinblastine as inducer. Current knowledge about the origin and properties of the limiting membranes of autophagic vacuoles, and the results of quantitative morphological studies into the dynamics and kinetics of vinblastine-induced autophagocytosis, as well as recent achievements in isolation and characterization of subclasses of autophagic vacuoles (autophagosomes and autolysosomes) are reviewed.     

Opposite effects of intraventricular and intracisternal administration of vasopressin on blood pressure in rats

Lysine-8-vasopressin (LVP) was injected into the lateral ventricle (ICV) or into the cisterna magna (c.m.) of ether-anesthetized rats. ICV injection of LVP decreased the blood pressure (BP), whereas c.m. administration increased it. The opposite effects of ICV versus c.m. administration of the peptide might be related to differences in brainstem versus limbic-midbrain structures in the regulation of blood pressure, and suggest that both mechanisms can be influenced by vasopressin.     

Data on the evolution of hormones. Investigations on imprinting evoked by oligopeptides exhibiting no hormonal activity

According to the present state of art, imprinting can also be evoked by di-, tri-, tetra- and heptapeptides exhibiting no hormonal activity, i.e., pretreatment with some of the oligopeptides leads to an enhancement of further hormone binding. Administration of symmetric and asymmetric molecules containing alanine resulted in positive, and negative imprinting respectively. The length of the molecule had no effect on the possibility of imprinting to develop. At the same time, the extent of imprinting evoked by molecules having no hormonal activity was approximately half of the imprinting seen in previous experiments when molecules having hormonal activity were applied. This observation indicates that in the phenomenon of development into a hormone the ability to evoke imprinting (to develop receptor memory) may be important. Thus, the development into a hormone is not an accidental event.     

Glutathione S-transferase polymorphisms influence the level of oxidative DNA damage and antioxidant protection in humans

The fem-3 gene of Caenorhabditis elegans was employed to determine the mutation frequency as well as the nature of mutations induced by low earth orbit space radiation ambient to Space Shuttle flight STS-76. Recovered mutations were compared to those induced by accelerated iron ions generated by the AGS synchrotron accelerator at Brookhaven National Laboratory. For logistical reasons, dauer larvae were prepared at TCU, transported to either Kennedy Space Center or Brookhaven National Laboratory, flown in space or irradiated, returned to TCU and screened for mutants. A total of 25 fem-3 mutants were recovered after the shuttle flight and yielded a mutation frequency of 2.1x10(-5), roughly 3.3-fold higher than the spontaneous rate of 6.3x10(-6). Four of the mutations were homozygous inviable, suggesting that they were large deletions encompassing fem-3 as well as neighboring, essential genes. Southern blot analyses revealed that one of the 25 contained a polymorphism in fem-3, further evidence that space radiation can induce deletions. While no polymorphisms were detected among the iron ion-induced mutations, three of the 15 mutants were homozygous inviable, which is in keeping with previous observations that high LET iron particles generate deficiencies. These data provide evidence, albeit indirect, that an important mutagenic component of ambient space radiation is high LET charged particles such as iron ions.     

Distribution of cadmium in selected organs of mice: effects of cadmium on organ contents of retinoids and beta-carotene

Cadmium was administered to 32 adult ICR mice i.p. in two single doses (0.25 and 0.5 mg CdCl2, per kg of b.w.). After 48 hours concentrations of cadmium in kidneys, liver, spleen, muscle (m. quadriceps femoris), ovaries and testes and the concentration of retinyl palmitate, retinol and beta-carotene in kidney, liver and testes were determined. Significantly higher cadmium concentration was found in liver, kidney and ovary in both experimental groups in comparison with the control group (p<0.001). In muscle, spleen and testis the cadmium level was higher, however not significantly. No significant differences in the concentration of retinyl palmitate, retinol and alpha-carotene in liver were found. Concentration of alpha-carotene in kidney and testis was significantly decreased in both groups administered with cadmium (p<0.001). Concentration of retinyl palmitate was significantly lower in testis in the group with higher cadmium level (p<0.001) and the concentration of retinol significantly decreased in kidney and testis of mice after an administration of 0.5 mg CdCl2/kg b.w.     

Effect of endorphin exposure at weaning on the endorphin and serotonin content of white blood cells and mast cells in adult rat

Hormonal imprinting takes place perinatally at the first encounter between the developing receptor and its target hormone, resulting in the accomplishment of normal receptor development. In the presence of an excess of target hormone or the absence of it, or an excess of related molecules which can be bound by the receptor, faulty imprinting develops with life-long consequences. In previous experiments neonatal endorphin exposure caused a decrease in endorphin and serotonin content of peritoneal mast cells of adult animals. In the present experiment 25-day-old (weaned) female rats received 2 microg endorphin, and the endorphin as well as serotonin content of adult mast cells and white blood cells was studied by flow cytometry and confocal microscopy. Peritoneal lymphocytes and blood monocytes contained significantly (p<0.01) less endorphin and peritoneal mast cells less serotonin (p<0.07, i.e. of questionable significance) than the untreated control. The results bring attention to the possibility of durable imprinting of differentiating cells later in life and to the durable (possibly life-long) effect of an endorphin excess (perhaps caused by injury) manifested in the change of endorphin and serotonin content of immune cells.     

Seasonal molecular timekeeping within the rat circadian clock

In temperate zones duration of daylight, i.e. photoperiod, changes with the seasons. The changing photoperiod affects animal as well as human physiology. All mammals exhibit circadian rhythms and a circadian clock controlling the rhythms is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN consists of two parts differing morphologically and functionally, namely of the ventrolateral (VL) and the dorsomedial (DM). Many aspects of SCN-driven rhythmicity are affected by the photoperiod. The aim of the present overview is to summarize data about the effect of the photoperiod on the molecular timekeeping mechanism in the rat SCN, especially the effect on core clock genes, clock-controlled genes and clock-related genes expression. The summarized data indicate that the photoperiod affects i) clock-driven rhythm in photoinduction of c-fos gene and its protein product within the VL SCN, ii) clock-driven spontaneous rhythms in clock-controlled, i.e. arginine-vasopressin, and in clock-related, i.e. c-fos, gene expression within the DM SCN, and iii) the core clockwork mechanism within the rat SCN. Hence, the whole central timekeeping mechanism within the rat circadian clock measures not only the daytime but also the time of the year, i.e. the actual season.     

The A-204C polymorphism in the cholesterol 7alpha-hydroxylase (CYP7A1) gene determines the cholesterolemia responsiveness to a high-fat diet

The aim of the study was to ascertain whether the A-204C polymorphism in the cholesterol 7 -hydroxylase (CYP7A1) gene plays any role in determining LDL-cholesterol (LDL-C) concentration responsiveness to a high-fat diet. The concentrations of total cholesterol and LDL-cholesterol were measured in eleven healthy men (age: 30.9+/-3.2 years; BMI: 24.9+/-2.7 kg/m(2);;) who were homozygous for either the -204A or -204C allele, after 3 weeks on a low-fat (LF) diet and 3 weeks on a high-fat (HF) diet. During both dietary regimens, the isocaloric amount of food was provided to volunteers; LF diet contained 22 % of energy as a fat and 2.2 mg of cholesterol/kg of body weight a day, HF diet 40 % of fat and 9.7 mg of cholesterol/kg of body weight a day. In six subjects homozygous for the -204C allele, the concentrations of cholesterol and LDL-cholesterol were significantly higher on HF than on LF diet (cholesterol: 4.62 vs. 4.00 mmol/l, p<0.05; LDL-C: 2.15 vs. 1.63 mmol/l, p<0.01, respectively); no significant change was observed in five subjects homozygous for the -204A allele. There were no other differences in lipid and lipoprotein-lipid concentrations. Therefore, the polymorphism in the cholesterol 7alpha-hydroxylase promotor region seems to be involved in the determination of cholesterol and LDL-C responsiveness to a dietary fat challenge.     

Expression and activation of Akt/protein kinase B in sexually immature and mature rat uterus

This study investigated the expression and activation of Akt/PKB in developing and adult rat uterus. Expression of Akt was observed in uteri from adult ovariectomized and 7–35-day-old rats and no changes were observed in response to in vivo estradiol treatment (1–100 μg/100 g b.w.). To examine the mechanisms of PKB/Akt activation, phosphorylation at Thr³⁰⁸ and Ser⁴⁷³ regulatory sites were studied in uteri. Akt was constitutively phosphorylated on Ser⁴⁷³ residue in the untreated, control uteri, while phosphorylation of Thr³⁰⁸ was observed only after estradiol 17β (E2) treatment. The effects of E2 treatment were age dependent, no response was induced in 11-day-old uteri, while in 28 days and older rats the activation of Akt at both regulatory sites, Ser⁴⁷³ and Thr³⁰⁸, increased, the first response was detected 2 h after treatment, reaching the highest rate at 6 h. The rate of phosphorylation was stronger at Ser⁴⁷³ residue. The results suggest that the regulation of Akt activation at two regulatory sites in rat uteri are different, phosphorylation of Thr³⁰⁸ seems to be entirely estrogen dependent, while the phosphorylation of Ser⁴⁷³ is regulated by other factors as well as estrogen.     

Time-varying effective mitral valve area: prediction and validation using cardiac MRI and Doppler echocardiography in normal subjects

Precise knowledge of the volume and rate of early rapid left ventricular (LV) filling elucidates kinematic aspects of diastolic physiology. The Doppler E wave velocity-time integral (VTI) is conventionally used as the estimate of early, rapid-filling volume; however, this implicitly requires the assumption of a constant effective mitral valve area (EMVA). We sought to evaluate whether the EMVA is truly constant throughout early, rapid filling in 10 normal subjects using cardiac magnetic resonance imaging (MRI) and contemporaneous Doppler echocardiography, which were synchronized via ECG. LV volume measurements as a function of time were obtained via MRI, and transmitral flow values were measured via Doppler echocardiography. The synchronized data were used to predict EMVA as a function of time during early diastole. Validation involved EMVA determination using 1) the short-axis echocardiographic images near the mitral valve leaflet tips, 2) the distance between leaflet tips in the echocardiographic parasternal long-axis view, and 3) the distance between leaflet tips from the MRI LV outflow tract view. Predicted EMVA values varied substantially during early rapid filling, and observed EMVA values agreed well with predictions. We conclude that the EMVA is not constant, and its variation causes LV volume to increase faster than is reflected by the VTI. These results reveal the mechanism of early rapid volumetric increase and directly affect the significance and physiological interpretation of the VTI of the Doppler E wave. Application to subjects in selected pathophysiological subsets is in progress.