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Biomedical subjects

M Ramirez

Publications and source records attributed to M Ramirez.

At least 37 records · Page 2Linked to original sources
PubMed1988

Aminopeptidase activity is asymmetrically distributed in selected zones of rat brain.

Levels of soluble aminopeptidase (AP), measured as arylamidase activity using L-Leucine-2-Naphthylamide (Leu-2-NA) as substrate, were determined in the soluble fraction of eleven zones of rat brain. Results showed that AP activity is asymmetrically distributed in frontal cortex and hypothalamus with both left sides having significantly higher levels of AP activity, respectively, than the right sides. Simultaneously, the activities of lactate dehydrogenase (LDH) and glutamate-oxalacetate aminotransferase (GOT) were measured in the same cerebral regions; no significant difference was recorded in these activities between either side of the rat brain in any of the zones studied. Provided that aminopeptidases are involved in the degradation of some endogenously released neuropeptides, the results suggest a new mode of expression of cerebral lateralization.

Aminopeptidases↗
PubMed1987

Correlation of continuous-wave Doppler assessment of chronic aortic regurgitation with hemodynamics and angiography.

Fifteen patients with chronic aortic regurgitation (AR) were studied by cardiac catheterization and continuous-wave (CW) Doppler echocardiography. The slope of the AR CW Doppler signal was higher in patients with severe AR (5.7 +/- 2.1 m/s2) than in those with moderate (2.5 +/- 1.3 m/s2) or mild (1.8 +/- 0.7 m/s2) AR (p less than 0.05). The slopes in patients with mild (less than or equal to 18 mm Hg), moderate (19 to 24 mm Hg) and severe (greater than 24 mm Hg) elevation of left ventricular end-diastolic pressure were significantly different (1.9 +/- 0.6, 3.3 +/- 1.2 and 7.1 +/- 0.4 m/s2, respectively, p less than 0.05). Patients with severe AR had shorter pressure half-times than those with mild AR (283 +/- 141 vs 820 +/- 393 ms, p less than 0.05). There was a significant correlation between the slope and left ventricular end-diastolic pressure (r = 0.80, p less than 0.001) and a weaker inverse correlation between pressure half-time and left ventricular end-diastolic pressure (r = -0.59, p less than 0.05). The end-diastolic pressure gradient estimated from CW Doppler using a simplified Bernoulli equation correlated poorly with the catheter measured gradient (r = 0.59, p less than 0.02). The slope of the CW Doppler signal is a better predictor of severity than pressure half-time and is affected by left ventricular end-diastolic pressure in addition to angiographic severity of AR.

Angiocardiography↗
PubMed1987

Expression of only one myelin basic protein allele in mouse is compatible with normal myelination.

Myelin deficiency (mld) is an autosomal recessive mutation in mice characterized by a severe myelin deficit in the central nervous system (CNS). The primary defect in mld is a reduction of the synthesis of the myelin basic protein (MBP) and probably lies in a regulatory element of the MBP gene. In young mld heterozygotes, the MBP mRNA and MBP levels are intermediate. In order to study whether reduced levels of MBP gene expression affect myelination, we determined the levels of MBP mRNA and MBP itself in mld heterozygous and control brains, at different ages during development. Total proteins and MBP were also measured in myelin isolated at 25 and 85 days of age. Myelin proteins were analyzed by SDS-PAGE. In addition, we carried out a morphometric analysis on 25- and 85-day-old optic nerves. Our results indicate that in spite of a roughly 50% reduction of MBP gene expression (compared to controls), the amounts of myelin isolated and the concentration of MBP in myelin were normal in heterozygous brains. Nevertheless, morphometric analyses of optic nerves, which myelinate later than the brainstem, showed thinner myelin sheaths in 25-day-old heterozygotes when compared to controls. This difference disappeared at 85 days of age. These results indicate that normal mice synthesize MBP in excess. The synthesis of this extramyelinic pool of MBP represents a safety factor allowing normal myelination to proceed even when MBP synthesis is severely reduced. In mld heterozygotes, a 30-50% reduction of this rate of synthesis can represent a limiting factor and locally delay myelin deposition without affecting the overall myelin content or myelin composition in heterozygous adult brains.

Aging↗
PubMed1986

Asymmetrical distribution of aminopeptidase activity in the cortex of rat brain.

The levels of soluble aminopeptidase (AP) activity were measured in the right and left frontal (FC), parietotemporal (PTC) and occipital (OC) cortex of male albino rat brains. The results showed more AP activity in the left cortex than in the right. Analyzing these results further, we found that the differences are significant for frontal cortex but not for parietotemporal nor occipital cortex. However, 76% of the rats were left-predominant for AP activity in the 3 cortical areas studied.

Aminopeptidases↗
PubMed1986

Prefrontal cortex excitability in early postnatally malnourished rats.

The effect of early postnatal malnutrition on the responsiveness of the rat prefrontal cortex was studied by determining excitability thresholds and fatigability to direct cortical stimulation. Malnutrition imposed during the period of rapid brain growth caused a significant increase of cortical chronaxie values as well as increased fatigability of direct cortical responses, indicating a detrimental effect on the axodendritic synapses. Since the prefrontal cortex plays an important role in the temporal organization of behavior, a dysfunction of this cortical area could be a causal link between nutritional and behavioral deficits.

Animal Population Groups↗
PubMed1985

Segmental aplasia of the uterine horn in a cat.

A 4.5-year-old female domestic longhair cat with a history of intermittent abdominal distention following estrus and infertility was admitted for routine vaccinations. Radiographs revealed 2 large blunt-ended tubular structures overlapping each other in the abdomen. Segmental aplasia of the right uterine horn was diagnosed following exploratory laparotomy and ovariohysterectomy.

Animals↗
PubMed1978

Increased granulocyte counts in recipients of plasma from leukapheresed rats: a dose response study.

Humoral factors are elaborated by animal and human donors during filtration leukapheresis. Plasma obtained from rats after leukapheresis (PPP) increases granulocyte yields when given to donors prior to leukapheresis. In our studies, it appears that (1) the effect of PPP is dose-related, and (2) the granulocytosis and the titer of neutrophil releasing activity are proportional to the duration of leukapheresis. On the basis of our findings, we recommend initiation of clinical studies using postleukapheresis plasma to improve granulocyte harvests and that a dose of 1.5 ml of PPP/kg appears to be a reasonable starting point.

Animals↗
PubMedDate not supplied

Stability of neutrophil-releasing activity of plasma obtained from leukapheresed rats and stored at 4 C.

When granulocyte-donor rats were treated prior to pheresis with plasma obtained from previously leukapheresed rats (PPP), granulocytosis and a significant increase in granulocyte yield were observed. Previous studies have demonstrated that such plasma stored at -150 C for up to two weeks preserved the neutrophil-releasing activity. This study demonstrates that neutrophil-releasing activity was satisfactorily preserved when plasma from previously leukapheresed rats was stored at 4 C for three weeks.

Animals↗