ENVIRONMENTAL AND HORMONAL CONTROL OF TURION GERMINATION IN MYRIOPHYLLUM VERTICILLATUM

Germination, or outgrowth, of Myriophyllum verticillatum turions involves a series of visible changes starting with reflexing of leaves followed by extension and curving of the axis, and then by root formation. Before abscission, turions grow out in response to long days (16 hr) but not short days (8 hr). After abscission, turions show maximal dormancy which can be fully broken by a cold treatment (4 C). Turions are heterogeneous in degree of dormancy and ability to respond to less complete dormancy-breaking treatments, e.g., long days at 20 C. Cytokinins (10^-6 m) break dormancy of non-cold-treated turions, whereas gibberellic acid (GA₃) is ineffective except at high concentrations (10^-3 m). Continuous treatment with cytokinins causes abnormal development after germination. GA₃, on the other hand, induces apparently normal development even at high concentration. Indoleacetic acid (IAA) induces outgrowth only at high concentrations (10^-3 - 10^-4 m), but these concentrations also produce abnormal development. Abscisic acid (ABA, 10^-5 m) retards outgrowth of cold-treated turions and can completely suppress it in non-cold-treated turions. The activity of ABA-like substances in turions remains about the same before and during germination, whereas other (unidentified) acidic inhibitors decrease markedly. The cytokinin activity changes in a complex pattern.     

Loud calls of adult male red howling monkeys (Alouatta seniculus)

Loud calls of adult male red howlers (Alouatta seniculus) inhabiting a deciduous and semideciduous open woodland site in Venezuela were recorded opportunistically and categorized by ear and sonographically as barks and roars. Five to six different bark syllables were identified as occurring singly or in sequences of doublets and triplets. In barks, spectral energy was concentrated in bands at 350-400 Hz, 900-1,100 Hz, 1,800-2,200 Hz and 3,000-3,500 Hz, but not all higher bands were present in each syllable. Roars appeared sonographically like prolonged barks composed of a pulsated preface, a long legato climax and a brief, fractionated and at times pulsated coda; each part varied internally to the ear and in acoustic structure. All loud calls were of the noisy type (nonharmonic energy over a broad frequency range). Acoustic characteristics of the calls are interpreted in terms of the subserving vocal tract anatomy. I compare loud calls of red howlers with those of mantled (A. palliata) and black (A. caraya) howlers.     

The effect of 5-fluorouracil on experimental acute pancreatitis

The present study was undertaken to elucidate the effects of different doses of 5-fluorouracil on experimental acute pancreatitis. Twelve mongrel dogs were used. Acute pancreatitis was induced by intraductal injection of sunflower-oil. Two groups of animals were treated with intravenous 5-fluorouracil: 1 mg/kg body weight for the first group of 5 animals, and 5 mg/kg body weight for the second one of 7 animals in subsequent three postoperative days. All the animals in the first group died within 24 to 36 hours due to acute haemorrhagic pancreatitis. All the animals in the second one survived longer than 36 hours. A statistically significant increase of serum amylase and lipase levels was found in pancreatitis with significant decrease of them during treatment. Three to 8 weeks later signs of chronic pancreatitis could be detected in surviving dogs.     

Time course of neutral red-induced autophagy in murine pancreatic acinar cells. A morphometrical and cytochemical study.

The knowledge of the time course of the influences of chemicals on autophagy is of great importance in the study of their modes of action and hence provides information relating the mechanism and dynamics of this catabolic process. Neutral red (NR) treatment has long been used to produce an accumulation of autolysosomes in different cell types. In the present study early (AV1), advanced (AV2) and late (AV3), as well as complex (fused) AVs (AVc) were distinguished. In our morphometrical measurements, we found all these AV subcompartments significantly expanded as early as 30 min after the injection of NR (0.4 mg/g b.wt.), i.e. a large number of AVs accumulated in the cells. Since cytoplasmic volume fraction (CVF) of AV increased 3-fold during this early period we conclude that, unlike vinblastine, NR is not a fusion inhibitor. Accumulation of AV1 (3-fold) in the presence of fusions possibly indicates that NR stimulates formation of AVs in this early period, after the accumulation of AVs continued. The maximal CVF of AVs were measured at 4 h, when 7.6% of the cytoplasmic volume was sequestered into the AV compartment, two third of which came from AV3. This finding indicates that NR is probably an inhibitor of intravacuolar degradation. However, the high rate of accumulation of AV2, AV3, and total AVs including a slower but still pronounced accumulation of AV1 cannot be explained solely from inhibition of degradation, but indicates a stimulated segregation (AV formation). Our results therefore argue for a possible coupling of the regulation of autophagic segregation and degradation since vinblastine and possibly some other degradation inhibitors were also found to stimulate AV formation in other studies. Another goal of this study was to follow the time course of changes in distribution of certain lysosomal enzymes after NR treatment. According to our enzyme cytochemical studies, acid phosphatase (AP) of untreated cells is mainly located in large and small lysosomal elements of the Golgi zone, aryl sulfatase B (AS) in trans-Golgi elements including pre-secretory granules and trimetaphosphatase (TP) in basal lysosomes. After NR injection TP seemed to appear first in AV1 whereas AP activity was characteristic of more advanced AVs. AS activity only occasionally appeared in AV3 and exclusively at late times after NR injection.     

Cellular mechanisms of the development of primary arterial hypertension

Modern views on the contraction and dilatation mechanisms of vessel smooth muscle cells are discussed. The data on main role of the cation-transport cell system function peculiarities in the primary arterial hypertension genesis, a relation cell hyperreactivity to those peculiarities and its genetical origin, are reported. It is supposed that the hereditary predisposition forms certain functional lability of cellular elements in different organism tissues, and, in consequence of that, the environmental influences can provoke the development of primary arterial hypertension.     

Low genetic diversity and limited genetic structure across the range of the critically endangered Mexican howler monkey (Alouatta palliata mexicana)

Genetic diversity provides populations with the possibility to persist in ever-changing environments, where selective regimes change over time. Therefore, the long-term survival of a population may be affected by its level of genetic diversity. The Mexican howler monkey (Alouatta palliata mexicana) is a critically endangered primate restricted to southeast Mexico. Here, we evaluate the genetic diversity and population structure of this subspecies based on 83 individuals from 31 groups sampled across the distribution range of the subspecies, using 29 microsatellite loci. Our results revealed extremely low genetic diversity (H_O = 0.21, H_E = 0.29) compared to studies of other A. palliata populations and to other Alouatta species. Principal component analysis, a Bayesian clustering method, and analyses of molecular variance did not detect strong signatures of genetic differentiation among geographic populations of this subspecies. Although we detect small but significant F_ST values between populations, they can be explained by a pattern of isolation by distance. These results and the presence of unique alleles in different populations highlight the importance of implementing conservation efforts in multiple populations across the distribution range of A. p. mexicana to preserve its already low genetic diversity. This is especially important given current levels of population isolation due to the extreme habitat fragmentation across the distribution range of this primate.     

Alpha 1-adrenoceptor blocking properties of spiroxatrine in rat aorta.

This preliminary study has analyzed the potential ability of the 5-HT1A ligand spiroxatrine to interact with vascular alpha 1-adrenoceptors. Norepinephrine and the selective alpha 1-adrenoceptor agonist, methoxamine, elicited concentration-dependent contractions of rat aortic rings. In contrast, (+/-)-spiroxatrine (from 10(-8) to 3.1X10(-7) M) was devoid of any effect on vascular tone per se, but shifted the concentration-response curves of norepinephrine and methoxamine to the right in a concentration-dependent manner with pA2 values of 8.48 +/- 0.22 and 8.93 +/- 0.33, respectively. Endothelium removal did not significantly affect the above pA2 values of (+/-)-spiroxatrine. These data, taken in concert, support the contention that (+/-)-spiroxatrine displays alpha 1-adrenoceptor blocking properties in rat aortic rings.     

Involvement of adenosine A1 and A2A receptors on guanosine-mediated anti-tremor effects in reserpinized mice

Parkinson’s disease (PD) signs and symptoms regularly include tremor. Interestingly, the nucleoside guanosine (GUO) has already proven to be effective in reducing reserpine-induced tremulous jaw movements (TJMs) in rodent models, thus becoming a promising antiparkinsonian drug. Here, we aimed at revealing the mechanism behind GUO antiparkinsonian efficacy by assessing the role of adenosine A₁ and A_2A receptors (A₁R and A_2AR) on GUO-mediated anti-tremor effects in the reserpinized mouse model of PD. Reserpinized mice showed elevated reactive oxygen species (ROS) production and cellular membrane damage in striatal slices assessed ex vivo and GUO treatment reversed ROS production. Interestingly, while the simultaneous administration of sub-effective doses of GUO (5 mg/kg) and SCH58261 (0.01 mg/kg), an A_2AR antagonist, precluded reserpine-induced TJMs, these were ineffective on reverting ROS production in ex vivo experiments. Importantly, GUO was able to reduce TJM and ROS production in reserpinized mouse lacking the A_2AR, thus suggesting an A_2AR-independent mechanism of GUO-mediated effects. Conversely, the administration of DPCPX (0.75 mg/kg), an A₁R antagonist, completely abolished both GUO-mediated anti-tremor effects and blockade of ROS production. Overall, these results indicated that GUO anti-tremor and antioxidant effects in reserpinized mice were A₁R dependent but A_2AR independent, thus suggesting a differential participation of adenosine receptors in GUO-mediated effects.