Showing papers by "University of Puerto Rico, Medical Sciences Campus published in 2002"

Changes in brain-derived neurotrophic factor and trkB receptor in the adult Rana pipiens retina and optic tectum after optic nerve injury.

Abstract: In this study we used immunocytochemistry to investigate the distribution of brain-derived neurotrophic factor (BDNF) and its receptor tyrosine kinase (trkB) in retina and optic tectum of the frog Rana pipiens during regeneration after axotomy. We also measured changes in BDNF mRNA in retina and tectum. Retrograde labeling was used to identify retinal ganglion cells (RGCs) prior to quantification of the BDNF immunoreactivity. In control animals, BDNF was found in the majority of RGCs and displaced amacrine cells and in some cells in the inner nuclear layer (INL). After axotomy, BDNF immunoreactivity was reduced in RGCs but increased in the INL. BDNF mRNA levels in the retina remained high before and after axotomy. Three months after axotomy, after reconnection to the target, the staining intensity of many of the surviving RGCs had partially recovered. In the control tectum, BDNF staining was present in ependymoglial cells and in neurons throughout layers 4, 6, 8, and 9. After axotomy, BDNF staining in tectal neurons became more intense, even though mRNA synthesis was transiently down-regulated. In control retinas, trkB receptor immunostaining was present in most RGCs; no significant changes were observed after axotomy. In control tectum, trkB was detected only in ependymoglial cells. After axotomy, many neuronal cell bodies were transiently labeled. Our data are consistent with the hypothesis that a considerable fraction of the BDNF normally present in RGCs is acquired from their targets in the tectum. However, there are also intraretinal sources of BDNF that could contribute to the survival of RGCs.

Inhibition of human breast carcinoma cell proliferation by ascorbate and copper.

Abstract: We tested the effect of different concentrations of ascorbic acid (AA), 50, 100, 250 mg/500 mg/dL) with copper sulfate (CS), 10 mg/dL) on human breast carcinoma (MDA-MB231) cell proliferation in vitro Cell proliferation was measured using a colori-metric assay (Cell proliferation kit II (XTT), Boehringer, NJ) The results of the mean absorbance of the tissue culture at different AA concentrations and a constant CS concentration were as follow: 082 +/- 003 (control, mean +/- SE), 064 +/- 002 (CS above); 048 +/- 003 (50 mg/dL) AA), 021 +/- 002 (100 mg/dL), 008 +/- 001 (250 mg/dL) AA, 060 +/- 005 (500 mg/dL) These results show that a combination of AA and CS inhibits human breast carcinoma cell proliferation in vitro This cell proliferation inhibitory effect is directly proportional to the AA concentration with the exception of the 500 mg/dL AA dose This chemotherapeutic effect was optimally enhanced when AA was added at a concentration of 250 mg/dL The AA concentrations of 500 mg/dL had a biphasic effect on tumor cell proliferation probably due to back and forth redox reactions between AA and dehydroascorbic acid in a closed system This study provides preliminary evidence that AA and SC can be used as biological response modifiers (BRM) for tumor growth inhibition

Orthomolecular oncology: a mechanistic view of intravenous ascorbate's chemotherapeutic activity.

Abstract: The effect of vitamin C in cancer has been a subject of great controversy; mainly because of the inconsistent results obtained by oral intakes of ascorbate when used as an anticancer agent. We believe the intravenous application of ascorbate will provide more consistent results in cancer patients since Vitamin C blood levels attained are substantially higher in a range proven cytotoxic to malignant cells. In this article we will present and discuss our proposed mechanism on the chemotherapeutic activity exhibited by ascorbate.

Amine Effects on Aggression in the Giant Tropical Freshwater Prawn Macrobrachium rosenbergii

Abstract: In the crayfish, relative status can be quite stable when previously isolated animals are paired for the first time, as long as they are not exposed to a different rival (Bovbjerg 1953; Lowe 1956; Krasne et al. 1997). However, if exposed to a new rival, status can change depending primarily on the body/claw size of the new rival and the prior experience of both animals (review in Atema and Cobb, 1980). In this type of model system, physiological and molecular changes associated with the status of an individual need to be observed during defined windows of time following periods of interaction among naive animals. This is not the case in the giant tropical freshwater prawn Macrobrachium rosenbergii, where social status is relatively fixed.

Plasma homocysteine concentrations in a population of rhesus monkeys (Macaca mulatta): reference ranges and accompanying plasma concentrations of folate and vitamin B12.

Abstract: The circulating level of homocysteine (Hcy) is recognized as a major independent risk factor for cardiovascular disease in humans. Nonhuman primates are being investigated to see whether they will be accurate models for Hcy indicators of cardiovascular dysfunction. Normal reference values are available in humans for Hcy as classified by age, gender, ethnic origin, and biological factors, however similar information in nonhuman primates had not been published previously. The purpose of this report is to provide normal Hcy values in a large group of nonhuman primates in light of age, gender, and physiologic state (pregnancy and lactation) and to compare these values to the same parameters in humans to highlight similar and dissimilar trends. In addition, plasma levels of folic acid and vitamin B(12), which are determinants of Hcy status in humans, are presented. Samples obtained from a troop of 149 rhesus monkeys (Macaca mulatta) fed a high protein commercial diet were analyzed for Hcy by using high-performance liquid chromatography. Folate and vitamin B(12) levels were determined by using an autoanalyzer. Results (mean [95% confidence interval]) for the entire troop were: Hcy, 4.5 (4.2-4.9) micromol/L; folic acid, 8.6 (8.0-9.1) micromol/L; and vitamin B(12), 673 (611-741) pmol/L. Quantitative values are similar to published values for another species of wild-caught macaques. Similar to trends noted for humans, male monkeys had higher Hcy values than did female animals, pregnant animals had lower values than did nonpregnant ones, and Hcy levels were inversely proportional to plasma folate and vitamin B(12) concentrations. However, homocysteine levels in rhesus monkeys did not vary consistently with age, whereas they increase with age in humans.

A-Current Diversity: Differences in Channel Hardware or Second Messengers?

Abstract: The pyloric network generates a rhythmic motor behavior that is continuously adaptive (Harris-Warrick et al 1992) This patterned activity is based not only on synaptic connectivity, but also on the unique firing properties of the component neurons There are many molecular devices that could establish different firing properties between neurons, ranging from relatively static mechanisms like differential gene expression, to more dynamic methods such as changes in ion channel phosphorylation states The strategies involved most likely reflect elementary principles of the system Defining these strategies for the pyloric network could provide insights into its dynamic nature