Biomedical subjects

P Lenzi

Publications and source records attributed to P Lenzi.

At least 19 recordsLinked to original sources

PubMed1999

Renal prostanoids: physiological relevance in healthy salt-depleted women.

The effective role played by prostanoids in the control of renal function has been investigated in healthy women with salt depletion. Salt depletion (SD2 group, n = 6) was induced by low sodium chloride dietary intake (< or = 60 mmol per day) and combined treatment with natriuretic and potassium-sparing drugs. At the end of the depletive treatment, the cumulative sodium deficit was 513 +/- 56 mmol. The renal function and urinary excretions of prostaglandin (PG) E2, 6-keto-PGF1 alpha (6KPGF) and thromboxane (Tx) B2 were evaluated during hypotonic polyuria. The basal values of plasma sodium and potassium concentrations, plasma renin activity (PRA) and urinary aldosterone excretion were determined before the induction of hypotonic polyuria. Paired studies were performed in the absence (control) and presence of indomethacin both in the SD2 group and in a previously studied group (N2, n = 6) of healthy women in normal sodium and potassium balance. Women in normal balance received 100 mg i.m. of indomethacin, salt-depleted women received only 50 mg (because 100 mg of the drug produced a prolonged anuria). In the SD2 vs. N2 group in the absence of treatment the following significant differences were found: (a) higher basal values of PRA and urinary aldosterone excretion; (b) higher urinary excretions of 6KPGF and TxB2 but not of PGE2; (c) lower values of urinary flow rate, creatinine clearance, absolute and fractional excretions of sodium and chloride, plasma osmolality and plasma electrolyte concentrations. The effects of the indomethacin have been assessed as percentage variations by using paired data for each experimental group. In the SD2 vs. N2 group the reduction in urinary excretions of 6KPGF, TxB2 and potassium as well as in creatinine clearance were not significantly different. On the other hand, the following were significantly different: (a) the lower reduction in PGE2 excretion; (b) the higher reduction in urinary flow rate and in CH2O; (c) the reductions in absolute and fractional excretions of sodium and chloride, and the increase in plasma potassium concentration, significant in the SD2 group but not in the N2 group. The data suggest that: (1) when stimulated by salt depletion the renal biosynthetic pathways of PGI2 and TxA2 showed greater sensitivity to indomethacin inhibition; (2) the effects of the neurohormonal systems activated by salt depletion were either modulated or mediated by renal prostanoids.

Adult↗

PubMed1998

Effects of experimental salt depletion on urinary prostanoid excretions in normal women.

The effects of moderate salt depletion on urinary excretions of prostanoids (PG)E2, 6-keto-PGF1alpha (6KPGF) and thromboxane (TX)B2 have been investigated in healthy women (SD group, n = 14). Salt depletion was obtained by combining a low sodium chloride dietary intake (< 60 mmol per day) with natriuretic and potassium sparing treatment. At the end of the treatment, the cumulative sodium deficit was 438 +/- 42 mmol (mean +/- SEM). Plasma renin activity (PRA) and urinary aldosterone excretion were determined in basal conditions. Renal functional exploration was performed during hypotonic polyuria (by oral water load) and subsequent moderate antidiuresis (by low dose infusion of an antidiuretic hormone analogue). In both phases, renal function was estimated by the clearance (cl.) method and the urinary concentrations of PGE2, 6KPGF and TXB2 by RIA method. The control group was composed of 20 healthy women in normal sodium and potassium balance (N group). Salt depletion was effective in increasing the basal values of plasma renin activity (PRA) and urinary aldosterone excretion. Moreover, it was effective in inducing the following during polyuria: (a) a depression of the diuretic response to water load in presence of a reduction in plasma osmolality; (b) a reduction in creatinine cl. in the absence of significant changes in mean arterial pressure; (c) an increase in the fractional reabsorption of sodium and chloride, in particular at the level of the diluting segments. Both in polyuria and in antidiuresis, the excretions of 6KPGF and TXB2 were higher in the SD vs. N group, while the excretion of PGE2 was not significantly different. In SD and N pooled groups, significant positive correlations were shown between basal PRA and urinary excretions during polyuria of 6KGPF and TXB2, (but not of PGE2) as well as between the excretions of the two metabolites. In conclusion, functionally effective salt depletion induces in healthy women a stimulation of renal synthesis of both prostacyclin and thromboxane. The excretory data do not give evidence of a similar effect on PGE2 synthesis.

6-Ketoprostaglandin F1 alpha↗

PubMed1998

Ultrastructure of rat atrial tissue after either perfusion-or immersion-fixation both in vivo and in vitro study: comparison of methodological reliability.

The present study compares, from a morphological point of view, the possible differences between perfusion- and immersion-fixation techniques performed on rat myocardium in order to evaluate their reliability. The data we obtained showed that when the two techniques are carried out with particular care, they do not present significant differences in tissue preservation. Furthermore, we also evaluated the ultrastructural of rat myocardium at the end of in vitro experiments. In this case, signs of subcellular changes, such as vacuolar degeneration, swollen mitochondria, intermyofibrillar myelin-like figures and enlargements of non specialized junctions of the intercalated discs can frequently occur. So, our results indicate that the morphological integrity of myocardium is not completely preserved during in vitro investigations.

Animals↗

PubMed1998

Diazepam reduces ultrastructural changes induced by noise stress in rat adrenal gland.

Male rats were exposed to noise for 6 running hours and the effects of pretreatment with the benzodiazepine diazepam on the adrenal gland were evaluated. Ultrastructural examination showed that, after noise exposure, zona reticularis cells resulted the more affected, exhibiting areas of diluted cytoplasm, disarranged endoplasmic reticulum, membrane vestigia and some altered mitochondria; diluted cytoplasmic areas appeared in noradrenaline-storing cells, too. On the contrary, zona reticularis cells from diazepam-pretreated and noise-exposed rats resulted significantly less altered, as well as the noradrenaline-storing cells. The present findings indicate that diazepam is able to exert some protective action on adrenal gland alterations due to noise exposure.

Adrenal Cortex↗

PubMed1997

SEM/TEM investigation of rat cardiac subcellular alterations induced by changing duration of noise stress.

BACKGROUND: Many studies have shown that loud noise is an environmental stressor. Noise exposure causes changes at different levels in living beings; the cardiovascular system, considered to be the most affected apparatus, has received much attention in both animals and humans. The present study investigated the effect of changing duration of noise stimulation on rat myocardium to determine whether the responses could be related to time. METHODS: The study was performed on young albino male rats. Three groups of animals were exposed to white noise (100 dBA) for 1, 6, and 12 hr, respectively, and samples of right atrium and ventricle were processed for ultrastructural examination. The subcellular organization of cardiomyocytes was examined by transmission and scanning electron microscopy, the latter being carried out with the modified osmium maceration method. RESULTS: After 1 hr of noise exposure, atrial and ventricular cardiomyocytes did not present significant alterations. After 6 hr, changes were observed in atrial tissue at the mitochondrial level, whereas the ventricular structure appeared unaffected. After 12 hr of treatment, in addition to the mitochondrial alterations, changes in atrial and ventricular myocardium, consisting of areas of enlargement in intercalated disc membranes and decreased density in sarcoplasm, were detected. CONCLUSIONS: The methods we applied for the visualization of cellular organelles allowed us to demonstrate that atrial tissue is primarily involved in stress response, especially at the mitochondrial level; a more prolonged time of exposure seems to be necessary for ventricular involvement.

Animals↗

PubMed1997

Effect of varying noise stress duration on rat adrenal gland: an ultrastructural study.

The present study was performed to examine the effect of varying duration of noise exposure on rat adrenal gland. Animals were exposed to noise for 1, 6 and 12 h continuously and the sections obtained from exposed rats were compared to those from corresponding controls. No significant ultrastructural changes were found in the zona glomerulosa, while mitochondria of the zona fasciculata showed matrix dilution and cristolysis after 1 and 12 h of noise stress. At all exposure times examined, the zona reticularis exhibited areas of diluted cytoplasm, disarranged endoplasmic reticulum, membrane vestigia and some altered mitochondria. Diluted cytoplasmic areas appeared in noradrenaline- and adrenaline-storing cells after 6 and 12 h of exposure, respectively. Our findings indicate that each zona of the adrenal cortex and the two cell types of adrenal medulla show a differential reaction to noise stress.

Adrenal Cortex↗

PubMed1997

Gender difference in noise stress-induced ultrastructural changes in rat myocardium.

Male and female rats were exposed to noise 6 h daily for 7 days running and the effect of stress was evaluated both on myocardium ultrastructure and plasma corticosterone level. Both sexes showed subcellular alterations of cardiomyocytes; mitochondria, in particular, which resulted the most affected organelles, exhibited diluted matrix and cristolysis; in some areas, the sarcoplasmic reticulum appeared vesiculated. Quantitative analysis of altered mitochondria revealed that atrial myocardium was more affected in males than in females. Moreover, corticosterone plasma assay showed, in exposed animals, a growing increase without significant gender differences. The present findings suggest a more marked involvement of male sex when challenged with noise stressor.

Animals↗

PubMed1996

Suramin-induced ultrastructural changes in the testis of albino rats.

The effect of chronic suramin administration on rat testis was evaluated. The animals were given the drug twice a week for two months, following a treatment schedule comparable to that used in cancer therapy. Light microscopic sections revealed vacuolizations near the basal lamina, germ cells very little differentiated, together with immature cells located in the lumen of seminiferous tubules. Ultrastructural changes were revealed in the form of a decrease in nuclear density with evaginations of the nuclear envelope and sometimes ruptures of the plasmatic membrane. Changes in the Sertoli cells consisted of cytoplasm vacuolizations, in which some lysosomes, containing degraded material such as myelin-like figures, were present.

Animals↗

PubMed1996

Brain capillary perfusion during sleep.

Brain capillary perfusion was evaluated in the different states of the wake-sleep cycle-quiet wakefulness (QW), quiet sleep (QS), and active sleep (AS)-in rats. The extent of the perfused capillary network was determined by intravascular distribution of a fluorescent marker. Evans blue (EB); it remained unchanged across the three behavioral conditions, QW, QS, and AS. The anatomical network was assessed by alkaline phosphatase (AP) endothelial staining, which is known to underestimate the number of existing capillaries. The resulting number of AP profiles were, therefore, significantly lower than the number of EB profiles, but the percentage of AP-stained capillaries that were perfused (96%) was also unchanged across the behavioral conditions. The results indicate that no capillary recruitment accompanies the wake-sleep cycle. Capillary surface area is a relevant factor in determining exchanges across the blood-brain barrier. In the absence of capillary recruitment (relative constancy of the surface area), the CBF changes during sleep should preferentially affect flow-limited with respect to diffusion-limited transport.

Animals↗

PubMed1996

Effective role of the renin-angiotensin system in the control of prostanoid synthesis and renal function in healthy women with moderate salt depletion.

The interaction between moderate salt depletion and urinary excretions of prostanoids (PGE2,6-keto-PGF1 alpha and TxB2), as well as the effective role of the activated renin-angiotensin system (RAS), in the control of renal function and urinary prostanoid excretions have been investigated in healthy women. Salt depletion (SD, n = 8) was induced by low sodium chloride dietary intake (< or = 60 mmol per day) and combined treatment with natriuretic and potassium sparing drugs. The cumulative sodium deficit was 381 +/- 55 mmol. The renal function and urinary excretion of prostanoids were evaluated during hypotonic polyuria (oral water load) and subsequent moderate antidiuresis (lysine-8-vasopressin (LVP) low-dose infusion). Basal plasma renin activity (PRA) and urinary aldosterone excretion were determined, before the water load, in both the SD group and control studies in normal balance of sodium and potassium (N, n = 20). Paired studies were performed in the absence and in the presence of enalapril in the same SD group, as well as in a subgroup, with normal sodium and potassium balance, previously studied (N3, n = 6). In the SD vs. N group, significantly higher values of PRA and urinary aldosterone excretion were found. The renal antinatriuretic mechanism was activated and the diuretic response to water load depressed. During polyuria, the urinary 6-keto-PGF1 alpha and TxB2 excretions were significantly higher, probably reflecting an increase in the renal synthesis of their precursors. During the late LVP infusion, the urinary PGE2 excretion was also significantly increased, in absence of significant differences in urinary flow rate. In both SD and N3 groups, enalapril decreased the mean arterial pressure (MAP). Despite the decrease in MAP, not significantly different in SD vs. N3 group, the drug did not significantly affect the creatinine clearance. Also, the urinary prostanoid excretions were not significantly affected by enalapril. However, in the SD group, but not in the N3 group, the drug was effective in significantly decreasing the absolute and fractional excretions of sodium and chloride. Moreover, the plasma potassium concentration significantly decreased, despite the concurrent decrease in urinary potassium excretion. The data suggest that: (1) in salt depletion, the prostanoid release from the renal cortical structures was stimulated; (2) the renal prostanoid synthesis, either activated (sodium depletion) or not (normal sodium and potassium balance), was not affected by the RAS pharmacological blockade in the short-term; (3) in salt depletion, the RAS blockade recruited a homeostatic mechanism responsible for the improved renal salt conservation, as well as for the redistribution of potassium between the extra- and intra-cellular compartments.

Adult↗

PubMed1996

The action of diazepam on noise-induced alterations in rat atrial tissue: an ultrastructural study.

The effects of pretreatment with a benzodiazepine, diazepam, on the atrial tissue of rats exposed to noise were studied by means of electron microscopy. Examination of ultrathin sections showed that acute stress caused swelling of mitochondria with cristolysis and matrix dissolution. In diazepam-pretreated and noise-exposed animals atrial cardiomyocytes did not reveal noteworthy changes in comparison with controls and the majority of mitochondria were well preserved. Present findings indicate that diazepam is able to exert a protective action on cardiac alterations due to noise exposure, especially at the mitochondrial level.

Animals↗

PubMed1995

Ultrastructural changes in atrial tissue of young and aged rats submitted to acute noise stress.

Young and senescent rats were exposed to audiogenic stress for 6 h running and the effects of the treatment on the atrial myocardium were evaluated. In both young and senescent animals subcellular alterations of atrial cardiomyocytes were seen, consisting mainly of changes at the mitochondrial level. In particular, sections from young treated rats exhibited swollen mitochondria with lysis of their cristae and dissolution of the matrix. An enlargement was observed of the space between the outer and inner membranes of the mitochondria, which also showed an increase in size. In addition, aged treated specimens revealed decreased density of the sarcoplasm and marked heterogeneity in the myofibril pattern with ruptures and loss of continuity of the myofilaments.

Age Factors↗

PubMed1994

Brain blood flow and extracerebral carotid circulation during sleep in rat.

Cerebral blood flow (CBF) and blood flow (BF) in extracerebral head structures were measured during the sleep-wake cycle in rats using radioactive microspheres. While no statistically significant changes occurred in the transition from Waking to quiet sleep (also referred to as synchronized or non-REM Sleep), CBF increased significantly in active sleep (AS, also referred to as desynchronized or REM Sleep) in all structures considered, with the sole exception of the cerebellum. In extracerebral head structures, no significant state-dependent BF changes were found. Factor Analysis however extracted a common factor accounting for BF variability in the external carotid circulation. This factor was uncorrelated with CBF changes in AS, suggesting independent regulation of the two vascular beds in this sleep state.

Animals↗

PubMed1994

Interactions between the renin-angiotensin system and prostanoids in modulating renal function in potassium-depleted healthy women.

Plasma renin activity (PRA) and urinary aldosterone excretion were determined in healthy women with normal potassium balance (N, n = 20) or experimental potassium depletion (KD). KD was induced by natriuretic treatment--associated with replacement of net NaCl and water losses--and low dietary potassium intake (< or = 10 mmol/d). By using different depletion patterns, three groups were obtained with cumulative potassium deficits (mean +/- SEM) of 160 +/- 43 (KD1, n = 8), 198 +/- 22 (KD2, n = 6) and 215 +/- 54 mmol (KD3, n = 6). The renal function by the clearance (cl.) method and urinary concentrations of prostaglandin E2 (PGE2), 6-keto-PGF1 alpha (6KPGF), and thromboxane B2 (TXB2) by the RIA method were estimated during hypotonic polyuria (oral water load) and subsequent moderate antidiuresis induced by low-dose infusion of lysine-8-vasopressin (LVP). 1. In all KD groups the depletion treatment significantly reduced both potassium plasma concentration (PK) and urinary potassium excretion while it increased basal PRA; the basal urinary aldosterone excretion was not significantly different from normokalemic controls. In the KD3 vs KD1 group the P kappa value was significantly lower. 2. In both KD2 and KD3 groups as compared to the N group, several hypokalemic-like renal dysfunctions--absent in the KD1 group--occurred. Particularly, in the KD2 + KD3 vs N group the renal ability in both urine diluting (water load) and concentrating (LVP infusion) was significantly impaired.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗

PubMed1994

Effect of continuous heat exposure on sleep during partial sleep deprivation.

This study examined the effects of continuous heat exposure on sleep structure during a partial sleep-deprivation regime. The experimental protocol was divided into three periods. After a baseline period (5 days and nights at 20 degrees C), the sleep of the subjects was restricted to the second half of the night (3 a.m.-7 a.m.) for four consecutive nights. The restricted-sleep period was followed by two recovery days and nights. During the deprivation and recovery periods, the ambient temperature was 20 degrees C for six of the 12 subjects and 35 degrees C for the others. Sleep, esophageal and mean skin temperatures were continuously recorded. At 20 degrees C, the expected effect of sleep debt was apparent. There were significant reductions in time spent awake and in latencies for sleep and stage 4 sleep. The duration of stage 4 sleep significantly increased during the four successive restricted-sleep nights, whereas esophageal temperature significantly decreased over the successive days. When heat was added, esophageal temperature decrease was weakened, and the significant increase in stage 4 duration seen at 20 degrees C was not found. The findings suggest that the heat load imposed in our experimental condition has a suppressive effect on sleep stage 4 increase, which is induced by sleep restriction. The hypothesis that an increase in this sleep stage serves as a mechanism for energy conservation should be also considered.

Adult↗

PubMed1994

Effects of angiotensin-converting enzyme inhibition on renal dysfunction induced by moderate potassium depletion in healthy women.

The role of the renin-angiotensin system in renal hypokalaemic dysfunction has been investigated by evaluating the effects of the angiotensin (AT)-converting enzyme inhibition by enalapril. Healthy women were studied either in normal potassium balance (N3, n = 6) or moderate potassium depletion (KD3, n = 6). Potassium depletion (KD) was induced by low potassium dietary intake (greater than or equal to 10 mmol per day) and natriuretic treatment associated with replacement of net NaCl and water losses; the cumulative potassium deficit achieved was 214 +/- 54 mmol. The renal function and the urinary excretions of some prostanoids (PGE2, 6-keto-PGF1 alpha, TxB2) were evaluated during hypotonic polyuria (oral water load) and subsequent moderate antidiuresis (lysine-8-vasopressin (LVP) low-dose infusion). Paired studies were performed in absence (control) and presence of enalapril. Basal plasma renin activity (PRA) and urinary aldosterone excretion were determined before the water load of control studies. Renal dysfunction typical of chronic KD occurred in the KD3 group, i.e. increase in PRA, decrease in creatinine clearance, depression of the diuretic response to water load, inhibition of distal fractional chloride reabsorption, and blunted efficacy of LVP in increasing the urinary solute concentration. The urinary prostanoid excretions were reduced. Basal urinary aldosterone excretion was not changed significantly. In KD3 group enalapril decreased mean arterial pressure (MAP), increased the plasma potassium concentration, improved the diuretic response to water load and corrected the impairment of the distal fractional chloride reabsorption. Despite the decrease in MAP enalapril did not affect significantly the creatinine clearance. Neither urinary prostanoid excretions nor the renal response to LVP were affected by the drug. The data suggest that in KD the increased activity of the renin-angiotensin system affected the renal function both through direct effects and through effects dependent on the angiotensin-supported secretions of aldosterone and probably of vasopressin. Finally, by comparing the effects of enalapril and indomethacin in experimental groups with an equivalent degree of KD, evidence is provided in favour of the interaction between renin-angiotensin and prostanoid systems in controlling the glomerular filtration rate and the salt and water handling by renal tubules.

Adult↗

PubMed1993

Spinal cord blood flow changes during the sleep-wake cycle in rat.

Regional spinal cord blood flow was measured in rats during the sleep-wake cycle with the use of radioactive microspheres. Spinal cord blood flow decreases from wakefulness to quiet (synchronized) sleep while increasing in active (desynchronized) sleep. Blood-flow changes depend on changes in vascular resistance whose mechanisms have yet to be elucidated. Blood-gas tension or mean arterial pressure, however, do not play a relevant causal role.

Animals↗

PubMed1993

Effects of hydroxylamine, digitonin and triton X-100 on photoreceptor (paraflagellar swelling) and photoreception of Euglena gracilis.

We present experiments that test the effects of agents commonly used in visual pigment investigations, namely hydroxylamine (NH2OH), digitonin and triton X-100, on the photoreceptor and photoreception of Euglena. Hydroxylamine reacts with free and opsin-bound retinal, in aqueous solution, to form stable oximes, whereas digitonin and triton X-100 are the most common extractants of rhodopsin. Since previous data indicate that the chromophore present in Euglena photoreceptor is retinal, we investigated the influence of these chemicals on this organelle. The effects of these agents were studied by means of phase contrast, fluorescence and transmission electron microscopy and photobehaviour experiments. Hydroxylamine inhibited the formation of the Euglena photoreceptor. Photoaccumulation experiments on hydroxylamine-treated cells showed that they are unable to perceive light. Digitonin solubilized the crystalline structure of the photoreceptor, whereas the triton effect was limited to the membranous structures of the cell, leaving the photoreceptor unimpaired.

Animals↗