Renal blood flow during exercise: understanding its measurement with Doppler ultrasound

The sympathetic nervous system (SNS) has a critical role in continuously coordinating responses to stimuli internal and external to the human body by appropriately modulating the activity of the organs it innervates. The SNS is activated in response to various physiological stressors, including exercise, which can involve a significant increase in SNS activity. An increase in SNS activity directed towards the kidneys causes vasoconstriction of afferent arterioles within the kidneys. This sympathetically mediated renal vasoconstriction decreases renal blood flow (RBF), causing significant blood flow redistribution towards active skeletal muscles during exercise. In research studies, different modes, intensities, and durations of exercise have been used to investigate the sympathetically mediated RBF response to exercise, and several methodological approaches have been used to quantify RBF. Doppler ultrasound provides noninvasive, continuous, real-time measurements of RBF and has emerged as a valid and reliable technique to quantify RBF during exercise. This innovative methodology has been applied in studies in which the RBF response to exercise has been examined in healthy young and older adults and patient populations such as those with heart failure and peripheral arterial disease. This valuable tool has enabled researchers to produce clinically relevant findings that have furthered our understanding of the effect of SNS activation on RBF in populations of health and disease. Therefore, the focus of this narrative review is to highlight the use of Doppler ultrasound in research studies that has provided important findings furthering our knowledge of the impact of SNS activation on RBF regulation in humans.

Short isocapnic hyperoxia affects indices of vascular remodeling and intercellular adhesion molecules in healthy men

In preparation for tracheal intubation during induction of anesthesia, the patient may be ventilated with 100% oxygen. To investigate the impact of acute isocapnic hyperoxia on endothelial activation and vascular remodeling, ten healthy young men (24±3 years) were exposed to 5-min normoxia (21% O2) and 10-min hyperoxia trials (100% O2). During hyperoxia, intercellular adhesion molecules (ICAM-1) (hyperoxia: 4.16±0.85 vs normoxia: 3.51±0.84 ng/mL, P=0.04) and tissue inhibitor matrix metalloproteinase 1 (TIMP-1) (hyperoxia: 8.40±3.84 vs normoxia: 5.73±2.15 pg/mL, P=0.04) increased, whereas matrix metalloproteinase (MMP-9) activity (hyperoxia: 0.53±0.11 vs normoxia: 0.68±0.18 A.U., P=0.03) decreased compared to the normoxia trial. We concluded that even short exposure to 100% oxygen may affect endothelial activation and vascular remodeling.

Reactive oxygen species play a modulatory role in the hyperventilatory response to poikilocapnic hyperoxia in humans

KEY POINTS

The proposed mechanism for the increased ventilation in response to hyperoxia includes a reduced brain CO₂ -[H⁺ ] washout-induced central chemoreceptor stimulation that results from a decrease in cerebral perfusion and the weakening of the CO₂ affinity for haemoglobin. Nonetheless, hyperoxia also results in excessive brain reactive oxygen species (ROS) formation/accumulation, which hypothetically increases central respiratory drive and causes hyperventilation. We then quantified ventilation, cerebral perfusion/metabolism, arterial/internal jugular vein blood gases and oxidant/antioxidant biomarkers in response to hyperoxia during intravenous infusion of saline or ascorbic acid to determine whether excessive ROS production/accumulation contributes to the hyperoxia-induced hyperventilation in humans. Ascorbic acid infusion augmented the antioxidant defence levels, blunted ROS production/accumulation and minimized both the reduction in cerebral perfusion and the increase in ventilation observed during saline infusion. Hyperoxic hyperventilation seems to be mediated by central chemoreceptor stimulation provoked by the interaction between an excessive ROS production/accumulation and reduced brain CO₂ -[H⁺ ] washout.

ABSTRACT

The hypothetical mechanism for the increase in ventilation ( V ̇ E ) in response to hyperoxia (HX) includes central chemoreceptor stimulation via reduced CO₂ -[H⁺ ] washout. Nonetheless, hyperoxia disturbs redox homeostasis and raises the hypothesis that excessive brain reactive oxygen species (ROS) production/accumulation may increase the sensitivity to CO₂ or even solely activate the central chemoreceptors, resulting in hyperventilation. To determine the mechanism behind the HX-evoked increase in V ̇ E , 10 healthy men (24 ± 4 years) underwent 10 min trials of HX under saline and ascorbic acid infusion. V ̇ E , arterial and right internal right jugular vein (ijv) partial pressure for oxygen (PO₂ ) and CO₂ (PCO₂ ), pH, oxidant (8-isoprostane) and antioxidant (ascorbic acid) markers, as well as cerebral blood flow (CBF) (Duplex ultrasonography), were quantified at each hyperoxic trial. HX evoked an increase in arterial partial pressure for oxygen, followed by a hyperventilatory response, a reduction in CBF, an increase in arterial 8-isoprostane, and unchanged PijvCO₂ and ijv pH. Intravenous ascorbic acid infusion augmented the arterial antioxidant marker, blunted the increase in arterial 8-isoprostane and attenuated both the reduction in CBF and the HX-induced hyperventilation. Although ascorbic acid infusion resulted in a slight increase in PijvCO₂ and a substantial decrease in ijv pH, when compared with the saline bout, HX evoked a similar reduction and a paired increase in the trans-cerebral exchanges for PCO₂ and pH, respectively. These findings indicate that the poikilocapnic hyperoxic hyperventilation is likely mediated via the interaction of the acidic brain interstitial fluid and an increase in central chemoreceptor sensitivity to CO₂ , which, in turn, seems to be evoked by the excessive ROS production/accumulation.

Influence of breathing on variation in cardiac stroke volume at the onset of cycling

PURPOSE

During cycling, the variation in cardiac stroke volume (SVV) is similar to that at rest. However, SVV may be influenced by ventilation at the start of cycling, e.g., by a Valsalva-like maneuver used to stabilize the body. This study evaluated the influence of ventilation on SV during initiation of cycling.

METHODS

Ten healthy recreationally physical active males (mean ± SD: age 26 ± 3 years, height 184 ± 9 cm, weight 85 ± 9 kg) cycled on an ergometer for four 30 s intervals at submaximal workloads while synchronizing ventilatory and cardiovascular variables derived from gas exchange and arterial pulse contour analysis, respectively.

RESULTS

At exercise onset, cardiac output increased by an instantaneous rise in heart rate and SV (P < 0.05). In contrast, blood pressure increased only after 15 s (P < 0.05), reflected in a decline in total peripheral resistance from exercise onset (P < 0.05). SVV was similar at rest (20 ± 6%) and during exercise (21 ± 5%) except for the first 5 s of exercise when a ~ 2.5-fold elevation (47 ± 6%; P < 0.05) was correlated to variation in respiratory frequency (= 0.71, P = 0.02) and tidal volume (R = 0.66, P = 0.04) but not to variation in heart rate or blood pressure. Stepwise multiple regression analysis indicated a respiratory frequency influence on SVV at the onset of ergometer cycling.

CONCLUSION

The data provide evidence for a ventilatory influence on SVV at the onset of cycling exercise.

Attendences on health to riverine population living in the banks of Amazon river, Amapa, Brazil

Introduction

The riverine population resident at banks of Amazon river (Amapá, Brazil) has particularities related to health-disease process and socioepidemiologic demands, that represents a challenge for appointment of professionals in the unique health system. The project Mandic Borderless has a purpose to attend, in a complete and humanized way, populations without assistance in places of difficult access.

Objectives

Describe the experience and results obtained from the health care to riverine population in the region along Amazon River, Amapá, Brazil, attended during an expedition in 2020. Descriptive cross-sectional survey. The health-care staff that performed the consultations was composed of doctor, dentists, nurses and medical students, who work in a college located in the interior of the state of São Paulo.

Results

About 4,500 riverine populations were attended indirectly and other 1,775 directly by many medical specialties, such as: clinical medicine, gynecology, pediatrics, ophthalmology, dermatology, ultrasonography, nursery and odontology work for free. And also collective health education actions were carried out, addressing topics such as: oral health, scabies, pediculosis (lice), first aid, hypertension, diabetes, sexually transmitted diseases prevention and contraceptive methods. More than 300 patients received toothpaste kits and were instructed about oral health.

Conclusions

The expedition collected data about isolate population showing their necessary and provide an innovated experience in the medical teachings, considering the knowledge about the disease health process and the integrated and humanity care.

Key messages

Provide for medical students a vision about communities who lives in a geographic isolation. There are necessary of an upgrade in access a basic e essential services for the riverine population.

KATP channels modulate cerebral blood flow and oxygen delivery during isocapnic hypoxia in humans

KEY POINTS

ATP-sensitive K⁺ (K_ATP ) channels mediate hypoxia-induced cerebral vasodilatation and hyperperfusion in animals. We tested whether K_ATP channels blockade affects the increase in human cerebral blood flow (CBF) and the maintenance of oxygen delivery (CDO₂ ) during hypoxia. Hypoxia-induced increases in the anterior circulation and total cerebral perfusion were attenuated under K_ATP channels blockade affecting the relative changes of brain oxygen delivery. Therefore, in humans, K_ATP channels activation modulates the vascular tone in the anterior circulation of the brain, contributing to CBF and CDO₂ responses to hypoxia.

ABSTRACT

ATP-sensitive K⁺ (K_ATP ) channels mediate hypoxia-induced cerebral vasodilatation and hyperperfusion in animals. We tested whether K_ATP channels blockade affects the increase in cerebral blood flow (CBF) and the maintenance of oxygen delivery (CDO₂ ) during hypoxia in humans. Nine healthy men were exposed to 5-min trials of normoxia and isocapnic hypoxia (IHX, 10% O₂ ) before (BGB) and 3 h after glibenclamide ingestion (AGB). Mean arterial pressure (MAP), arterial saturation ( S a O 2 ), partial pressure of oxygen ( P a O 2 ) and carbon dioxide ( P aC O 2 ), internal carotid artery blood flow (ICABF), vertebral artery blood flow (VABF), total (t)CBF (Doppler ultrasound) and CDO₂ were quantified during the trials. IHX provoked similar reductions in S a O 2 and P a O 2 , while MAP was not affected by oxygen desaturation or K_ATP blockade. A smaller increase in ICABF (ΔBGB: 36 ± 23 vs. ΔAGB 11 ± 18%, p = 0.019) but not in VABF (∆BGB 26 ± 21 vs. ∆AGB 27 ± 27%, p = 0.893) was observed during the hypoxic trial under K_ATP channels blockade. Thus, IHX-induced increases in tCBF (∆BGB 32 ± 19 vs. ∆AGB 14 ± 13%, p = 0.012) and CDO₂ relative changes (∆BGB 7 ± 13 vs. ∆AGB -6 ± 14%, p = 0.048) were attenuated during the AGB hypoxic trial. In a separate protocol, 6 healthy men (5 from protocol 1) underwent a 5-min exposure to normoxia and IHX before and 3 h after placebo (5 mg of cornstarch) ingestion. IHX reduced S a O 2 and P a O 2 , but placebo did not affect the ICABF, VABF, tCBF, or CDO₂ responses. Therefore, in humans, K_ATP channels activation modulates vascular tone in the anterior rather than the posterior circulation of the brain, contributing to tCBF and CDO₂ responses to hypoxia.

Differential vasomotor responses to isocapnic hyperoxia: cerebral versus peripheral circulation

Isocapnic hyperoxia (IH) evokes cerebral and peripheral hypoperfusion via both disturbance of redox homeostasis and reduction in nitric oxide (NO) bioavailability. However, it is not clear whether the magnitude of the vasomotor responses depends on the vessel network exposed to IH. To test the hypothesis that the magnitude of IH-induced reduction in peripheral blood flow (BF) may differ from the hypoperfusion response observed in the cerebral vascular network under oxygen-enriched conditions, nine healthy men (25 ± 3 yr, mean ± SD) underwent 10 min of IH during either saline or vitamin C (3 g) infusion, separately. Femoral artery (FA), internal carotid artery (ICA), and vertebral artery (VA) BF (Doppler ultrasound), as well as arterial oxidant (8-isoprostane), antioxidant [ascorbic acid (AA)], and NO bioavailability (nitrite) markers were simultaneously measured. IH increased 8-isoprostane levels and reduced nitrite levels; these responses were followed by a reduction in both FA BF and ICA BF, whereas VA BF did not change. Absolute and relative reductions in FA BF were greater than IH-induced changes in ICA and VA perfusion. Vitamin C infusion increased arterial AA levels and abolished the IH-induced increase in 8-isoprostane levels and reduction in nitrite levels. Whereas ICA and VA BF did not change during the vitamin C-IH trial, FA perfusion increased and reached similar levels to those observed during normoxia with saline infusion. Therefore, the magnitude of IH-induced reduction in femoral blood flow is greater than that observed in the vessel network of the brain, which might involve the determinant contribution that NO has in the regulation of peripheral vascular perfusion.

Muscle sympathetic nerve activity and hemodynamic responses to venous distension: does sex play a role?

Peripheral venous distension mechanically stimulates type III/IV sensory fibers in veins and evokes pressor and sympathoexcitatory reflex responses in humans. As young women have reduced venous compliance and impaired sympathetic transduction, we tested the hypothesis that pressor and sympathoexcitatory responses to venous distension may be attenuated in women compared with men. Mean arterial pressure (photoplethysmography), heart rate (HR), stroke volume (SV; Modelflow), cardiac output (CO = HR × SV), muscle sympathetic nerve activity (MSNA), femoral artery blood flow, and femoral artery conductance (Doppler ultrasound) were quantified in eight men (27 ± 4 yr) and nine women (28 ± 4 yr) before [control (CON)], during (INF), and immediately after (post-INF) a local infusion of saline [5% of the total forearm volume (30 ml/min); the infusion time was 2 ± 1 and 1 ± 1 min ( P = 0.0001) for men and women, respectively] through a retrograde catheter inserted into an antecubital vein, to which venous drainage and arterial supply had been occluded. Mean arterial pressure increased during and after infusion in both groups (vs. the CON group, P < 0.05), but women showed a smaller pressor response in the post-INF period (Δ+7.2 ± 2.0 vs. Δ+18.3 ± 3.9 mmHg in men, P = 0.019). MSNA increased and femoral artery conductance decreased similarly in both groups (vs. the CON group, P < 0.05) at post-INF. Although HR changes were similar, increases in SV (Δ+20.4 ± 8.6 vs. Δ+2.6 ± 2.7 ml, P = 0.05) and CO (Δ+0.84 ± 0.17 vs. Δ+0.34 ± 0.10 l/min, P = 0.024) were greater in men compared with women. Therefore, venous distension evokes a smaller pressor response in young women due to attenuated cardiac adjustments rather than reduced venous compliance or sympathetic transduction. NEW & NOTEWORTHY We found that the pressor response to venous distension was attenuated in young women compared with age-matched men. This was due to attenuated cardiac adjustments rather than reduced venous compliance, sympathetic activation, or impaired transduction and vascular control. Collectively, these findings suggest that an attenuated venous distension reflex could be involved in orthostatic intolerance in young women.

Human brain blood flow and metabolism during isocapnic hyperoxia: the role of reactive oxygen species

KEY POINTS

It is unknown whether excessive reactive oxygen species (ROS) production drives the isocapnic hyperoxia (IH)-induced decline in human cerebral blood flow (CBF) via reduced nitric oxide (NO) bioavailability and leads to disruption of the blood-brain barrier (BBB) or neural-parenchymal damage. Cerebral metabolic rate for oxygen (CMR O 2 ) and transcerebral exchanges of NO end-products, oxidants, antioxidants and neural-parenchymal damage markers were simultaneously quantified under IH with intravenous saline and ascorbic acid infusion. CBF and CMR O 2 were reduced during IH, responses that were followed by increased oxidative stress and reduced NO bioavailability when saline was infused. No indication of neural-parenchymal damage or disruption of the BBB was observed during IH. Antioxidant defences were increased during ascorbic acid infusion, while CBF, CMR O 2 , oxidant and NO bioavailability markers remained unchanged. ROS play a role in the regulation of CBF and metabolism during IH without evidence of BBB disruption or neural-parenchymal damage.

ABSTRACT

To test the hypothesis that isocapnic hyperoxia (IH) affects cerebral blood flow (CBF) and metabolism through exaggerated reactive oxygen species (ROS) production, reduced nitric oxide (NO) bioavailability, disturbances in the blood-brain barrier (BBB) and neural-parenchymal homeostasis, 10 men (24 ± 1 years) were exposed to a 10 min IH trial (100% O₂ ) while receiving intravenous saline and ascorbic acid (AA, 3 g) infusion. Internal carotid artery blood flow (ICABF), vertebral artery blood flow (VABF) and total CBF (tCBF, Doppler ultrasound) were determined. Arterial and right internal jugular venous blood was sampled to quantify the cerebral metabolic rate of oxygen (CMR O 2 ), transcerebral exchanges (TCE) of NO end-products (plasma nitrite), antioxidants (AA and AA plus dehydroascorbic acid (AA+DA)) and oxidant biomarkers (thiobarbituric acid-reactive substances (TBARS) and 8-isoprostane), and an index of BBB disruption and neuronal-parenchymal damage (neuron-specific enolase; NSE). IH reduced ICABF, tCBF and CMR O 2 , while VABF remained unchanged. Arterial 8-isoprostane and nitrite TCE increased, indicating that CBF decline was related to ROS production and reduced NO bioavailability. AA, AA+DA and NSE TCE did not change during IH. AA infusion did not change the resting haemodynamic and metabolic parameters but raised antioxidant defences, as indicated by increased AA/AA+DA concentrations. Negative AA+DA TCE, unchanged nitrite, reductions in arterial and venous 8-isoprostane, and TBARS TCE indicated that AA infusion effectively inhibited ROS production and preserved NO bioavailability. Similarly, AA infusion prevented IH-induced decline in regional and total CBF and re-established CMR O 2 . These findings indicate that ROS play a role in CBF regulation and metabolism during IH without evidence of BBB disruption or neural-parenchymal damage.

Reduced arterial vasodilatation in response to hypoxia impairs cerebral and peripheral oxygen delivery in hypertensive men

KEY POINTS

Hypoxaemia evokes a repertoire of homeostatic adjustments that maintain oxygen supply to organs and tissues including the brain and skeletal muscles. Because hypertensive patients have impaired endothelial-dependent vasodilatation and an increased sympathetic response to arterial oxygen desaturation, we investigated whether hypertension impairs isocapnic hypoxia-induced cerebral and skeletal muscle hyperaemia to an extent that limits oxygen supply. In middle-aged hypertensive men, vertebral and femoral artery blood flow do not increase in response to isocapnic hypoxia, limiting brain and peripheral hyperaemia and oxygen supply. Increased chemoreflex-induced sympathetic activation impairs skeletal muscle perfusion and oxygen supply, whereas an attenuation of local vasodilatory signalling in the posterior cerebrovasculature reduced brain hyperperfusion of hypertensive middle-aged men in response to isocapnic hypoxia.

ABSTRACT

The present study investigated whether hypertension impairs isocapnic hypoxia (IH)-induced cerebral and skeletal muscle hyperaemia to an extent that limits oxygen supply. Oxygen saturation (oxymetry), mean arterial pressure (photoplethysmography) and muscle sympathetic nerve activity (MSNA; microneugraphy), as well as femoral artery (FA), internal carotid artery and vertebral artery (VA) blood flow (BF; Doppler ultrasound), were quantified in nine normotensive (NT) (aged 40 ± 11 years, systolic pressure 119 ± 7 mmHg and diastolic pressure 73 ± 6 mmHg) and nine hypertensive men (HT) (aged 44 ± 12 years, systolic pressure 152 ± 11 mmHg and diastolic pressure 90 ± 9 mmHg) during 5 min of normoxia (21% O₂ ) and IH (10% O₂ ). Total cerebral blood flow (tCBF), brain (CDO₂ ) and leg (LDO₂ ) oxygen delivery were estimated. IH provoked similar oxygen desaturation without changing mean arterial pressure. Internal carotid artery perfusion increased in both groups during IH. However, VA and FA BF only increased in NT. Thus, IH-induced increase in tCBF was smaller in HT. CDO₂ only increased in NT and LDO₂ decreased in HT. Furthermore, IH evoked a greater increase in HT MSNA. Changes in MSNA were inversely related to FA BF, LDO₂ and end-tidal oxygen tension. In conclusion, hypertension disturbs regional and total cerebrovascular and peripheral responses to IH and consequently limits oxygen supply to the brain and skeletal muscle. Although increased chemoreflex-induced sympathetic activation may explain impaired peripheral perfusion, attenuated vasodilatory signalling in the posterior cerebrovasculature appears to be responsible for the small increase in tCBF when HT were exposed to IH.

Discriminating between virilizing ovary tumors and ovary hyperthecosis in postmenopausal women: clinical data, hormonal profiles and image studies

BACKGROUND

The presence of virilizing signs associated with high serum androgen levels in postmenopausal women is rare. Virilizing ovarian tumors (VOTs) and ovarian stromal hyperthecosis (OH) are the most common etiologies in virilized postmenopausal women. The differential diagnosis between these two conditions is often difficult.

OBJECTIVE

To evaluate the contribution of clinical features, hormonal profiles and radiological studies to the differential diagnosis of VOT and OH.

DESIGN

A retrospective study.

SETTING

A tertiary center.

MAIN OUTCOME MEASURES

Clinical data, hormonal status (T, E2, LH and FSH), pelvic images (transvaginal sonography and MRI) and anatomopathology were reviewed.

PATIENTS

Thirty-four postmenopausal women with a diagnosis of VOT (13 women) and OH (21 women) were evaluated retrospectively.

RESULTS

Clinical signs of hyperandrogenism were more prevalent in the VOT group than the OH group. Although the VOT group showed higher T and E2 levels and lower gonadotropin levels than the OH group, a great overlap occurred among the hormone levels. A pelvic MRI provided an accurate differentiation of these two conditions.

CONCLUSION

In this group of patients, the main features contributing to the differential diagnosis of VOT and OH were serum levels of testosterone and gonadotropins and the presence of an ovarian nodule identified on the MRI. Although the association of clinical, hormonal and radiological features contributes to the differential diagnosis of these two conditions, histopathological analysis remains the gold standard for the diagnosis of ovarian hyperandrogenism in postmenopausal women.

Selective α1-adrenergic blockade disturbs the regional distribution of cerebral blood flow during static handgrip exercise

Handgrip-induced increases in blood flow through the contralateral artery that supplies the cortical representation of the arm have been hypothesized as a consequence of neurovascular coupling and a resultant metabolic attenuation of sympathetic cerebral vasoconstriction. In contrast, sympathetic restraint, in theory, inhibits changes in perfusion of the cerebral ipsilateral blood vessels. To confirm whether sympathetic nerve activity modulates cerebral blood flow distribution during static handgrip (SHG) exercise, beat-to-beat contra- and ipsilateral internal carotid artery blood flow (ICA; Doppler) and mean arterial pressure (MAP; Finometer) were simultaneously assessed in nine healthy men (27 ± 5 yr), both at rest and during a 2-min SHG bout (30% maximal voluntary contraction), under two experimental conditions: 1) control and 2) α1-adrenergic receptor blockade. End-tidal carbon dioxide (rebreathing system) was clamped throughout the study. SHG induced increases in MAP (+31.4 ± 10.7 mmHg, P < 0.05) and contralateral ICA blood flow (+80.9 ± 62.5 ml/min, P < 0.05), while no changes were observed in the ipsilateral vessel (−9.8 ± 39.3 ml/min, P > 0.05). The reduction in ipsilateral ICA vascular conductance (VC) was greater compared with contralateral ICA (contralateral: −0.8 ± 0.8 vs. ipsilateral: −2.6 ± 1.3 ml·min−1·mmHg−1, P < 0.05). Prazosin was effective to induce α1-blockade since phenylephrine-induced increases in MAP were greatly reduced ( P < 0.05). Under α1-adrenergic receptor blockade, SHG evoked smaller MAP responses (+19.4 ± 9.2, P < 0.05) but similar increases in ICAs blood flow (contralateral: +58.4 ± 21.5 vs. ipsilateral: +54.3 ± 46.2 ml/min, P > 0.05) and decreases in VC (contralateral: −0.4 ± 0.7 vs. ipsilateral: −0.4 ± 1.0 ml·min−1·mmHg−1, P > 0.05). These findings indicate a role of sympathetic nerve activity in the regulation of cerebral blood flow distribution during SHG.

Assessment of extended-spectrum β-lactamase, KPC carbapenemase and porin resistance mechanisms in clinical samples of Klebsiella pneumoniae and Enterobacter spp

The emergence and spread of resistance mechanisms in Gram-negative bacilli has complicated the treatment of serious nosocomial infections. Current automated systems for detection of Klebsiella pneumoniae carbapenemase (KPC)-producing isolates are unreliable. One possible straightforward alternative method is evaluation of ertapenem resistance. However, the accuracy of this method is affected by other resistance mechanisms such as AmpC gene expression or extended-spectrum β-lactamase production associated with porin loss. This study included 128 samples of K. pneumoniae and Enterobacter spp. that were non-susceptible to ertapenem. The disk diffusion and Etest method were applied to determine susceptibility to imipenem, meropenem and ertapenem. Isolates exhibiting intermediate or complete resistance to ertapenem were evaluated for resistance mechanisms. bla(TEM), bla(SHV), bla(CTX-M), bla(CTX-M-2) and bla(KPC) genes were tested for by PCR, and the presence of outer membrane protein was investigated by dot-blot assay. bla(TEM) was detected in 52.9% and 10.3%, bla(SHV) in 29.4% and 0.94%, bla(CTX-M) in 41.4% and 1.9% and bla(CTX-M-2) in 23.5% and 1.9% of K. pneumoniae and Enterobacter cloacae isolates, respectively. The bla(KPC) gene was present in 12.6% of Enterobacter spp. isolates. OmpC and OmpF were present in 6.6% of E. cloacae isolates. These results indicate that several resistance mechanisms contribute to potential therapeutic failure of carbapenem therapy and point to the need for better detection methods and surveillance strategies.

Effect of Vernonia cognata on oxidative damage induced by ethanol in rats

Free radicals production and oxidative stress play a central role in injuries caused by ethanol (EtOH) on gastric mucosal. Thus, strategies to counteract EtOH toxicity are highly desirable. This study was aimed at evaluating whether Vernonia cognata extract would reduce EtOH effects in rats. Rats received Vernonia cognata extract (0, 1 and 2 g/kg bw, by gavage) 1 hour after EtOH had been administered (0 or 70%, 0.5 mL/100 g bw, by gavage) and were killed 1 hour after Vernonia cognata extract administration. The stomach was removed for macroscopic and histopathological evaluation, as well as, oxidative stress markers such as lipoperoxidation (LPO) and non-protein thiol groups (NPSH) levels and catalase (CAT) activity. EtOH acute exposure increased LPO and decreased NPSH levels and CAT activity along with macroscopic and microscopic lesions in gastric tissue, confirming the involvement of oxidative stress in EtOH toxicity. Vernonia cognata extract attenuated oxidative and histopathological features induced by EtOH at all evaluated doses. Moreover, both studied doses of Vernonia cognata extract caused an increase in NPSH levels per se. However, only the dose of 2 g/kg reverted all macroscopic changes caused by EtOH toxicity. The protective effect of the extract could be attributed to antioxidant molecules present in the extract, such as flavonoids and phenolic acids, which were quantified by high performance liquid chromatography (HPLC). Thus, an antioxidant effect of the extract leads to a protection on gastric tissue. Our results indicate that Vernonia cognata hydroethanolic extract could have a beneficial role against EtOH toxicity by preventing oxidative stress and gastric tissue injury.

Effect of astaxanthin on kidney function impairment and oxidative stress induced by mercuric chloride in rats

Reactive oxygen species are implicated as mediators of tissue damage in the acute renal failure induced by inorganic mercury. Astaxanthin (ASX), a carotenoid with potent antioxidant properties, exists naturally in various plants, algae, and seafoods. This paper evaluated the ability of ASX to prevent HgCl(2) nephrotoxicity. Rats were injected with HgCl(2) (0 or 5 mg/kg b.w., sc) 6h after ASX had been administered (0, 10, 25, or 50mg/kg, by gavage) and were killed 12h after HgCl(2) exposure. Although ASX prevented the increase of lipid and protein oxidation and attenuated histopathological changes caused by HgCl(2) in kidney, it did not prevent creatinine increase in plasma and delta-aminolevulinic acid dehydratase inhibition induced by HgCl(2). Glutathione peroxidase and catalase activities were enhanced, while superoxide dismutase activity was depressed in HgCl(2)-treated rats when compared to control and these effects were prevented by ASX. Our results indicate that ASX could have a beneficial role against HgCl(2) toxicity by preventing lipid and protein oxidation, changes in the activity of antioxidant enzymes and histopathological changes.

Longitudinal differentiation in Melipona mandacaia (Hymenoptera, Meliponini) chromosomes

Melipona mandacaia is a stingless bee endemic to northeast Brasil. We describe the M. mandacaia karyotype using C-banding technique. fluorochrome staining and treatment with restriction enzymes and discuss the position of this species in the context of the phylogeny of the genus. Melipona mandacaia has 2n = 18 (14 SM + 2 M + 2 A). Heterochromatin was detected in the pericentromeric region of pairs 1, 2 and 8 and in the form of small blocks in the remaining pairs. Staining with base-specific fluorochromes showed that this heterochromatin was rich AT (QM and DAPI), except in the region corresponding to the NOR which was rich GC (CMA3) and was cleaved by the HaeIII enzyme. Melipona mandacaia is a member of Group I Melipona. Treatment with DraI/Giemsa discloses a larger number of bands than treatment with DraI/QM. Pre-cleavage with DraI gave rise to a larger number of bands following QM staining; a circumstance evidently due to a removal of the DNA-protein complex that prevented the association of the fluorochrome with AT-rich DNA. The results highlight the complex nature of heterochromatin.

Indium square root 7 x square root 3 on Si(111): a nearly free electron metal in two dimensions

We present measurements of the Fermi surface and underlying band structure of a single layer of indium on Si(111) with square root 7 x square root 3 periodicity. Electrons from both indium valence electrons and silicon dangling bonds contribute to a nearly free, two-dimensional metal on a pseudo-4-fold lattice, which is almost completely decoupled at the Fermi level from the underlying hexagonal silicon lattice. The mean free path inferred from our data is quite long, suggesting the system might be a suitable model for studying the ground state of two-dimensional metals.

Silver staining of nucleolar organizer regions (NOR) in some species of Hymenoptera (bees and parasitic wasp) and Coleoptera (lady-beetle)

Adaptations of the nucleolar organizer regions (NOR) banding technique using precipitation of silver salts significantly improved the NOR characterization of some species of hymenopterans and one coleopteran. The bee Melipona marginata (2n = 18) showed one metacentric pair of chromosomes with a NOR in the pericentromeric position. The parasitic wasp Mellitobia australica (2n = 12) also showed one metacentric pair with a strongly Ag-positive NOR. The male lady-beetle Cycloneda sanguinea (2n = 18 + Xy(p)) displayed a NOR on a pair of acrocentric autosomes. In the male Euglossa sp. (a haplodiploid species) (n = 21) the NOR were multiple, and occurred in five chromosomes. In the bee Plebeia sp. 1 (2n = 34) the NOR seemed restricted to one of the homologues of a metacentric pair. The systematic advances brought out by using this technique in the context of current theories of karyotypic evolution of these taxa are described and discussed.

Effect of chemically induced propionic acidemia on neurobehavioral development of rats

High levels of propionic acid (PPA) comparable to those of human propionic acidemia were achieved in blood (1-5 mmol/l) and brain (1 micromol/g) of rats by administering saline-buffered propionate (pH 7.4) subcutaneously twice a day from the 6th to the 28th day of life. PPA doses ranged from 1.44 to 1.92 micromol/g body weight as a function of animal age. Control rats were treated with saline in the same volumes. Growth and development of physical landmarks were assessed by monitoring the following parameters daily: body weight, upper incisor eruption, eye opening, and hair coat. Development of some reflexes was also monitored, and a specific subset of motor skills was evaluated at days 14 and 21 of life by the free-fall righting test and the spontaneous alternation test. Chronic PPA administration had no effect on body weight, cerebral cortex weight, or cerebellum weight, but caused slight but significant delays in the day of appearance of hair coat and eye opening, indicating an effect of PPA on the development of physical parameters. Free-fall righting was impaired in PPA-treated animals. On the other hand, PPA administration had no effect on the performance of the animals in the spontaneous alternation tests. Long-term effects of early PPA administration were investigated by assessing animal performance in an aversive task (two-way shuttle avoidance task) and in a nonaversive (open-field task) behavioral task at 60 days of age. PPA-treated rats did not habituate to the open field, and presented a lack of retention of the shuttle-avoidance task. Our results suggest that early postnatal PPA administration to rats alters normal development and induces long-term behavioral deficits in aversive and nonaversive tasks.

Inhibition of mitogen-activated proliferation of human peripheral lymphocytes in vitro by propionic acid

Recurrent infections are common features in patients affected by propionic acidaemia (McKusick 232000) and methylmalonic acidaemia (McKusick 251000). Since these disorders are biochemically characterized by tissue accumulation of propionic acid and methylmalonic acid respectively, it is possible that these compounds may act as immunosuppressants. We therefore investigated the effect of propionate and methylmalonate on cellular growth of human peripheral lymphocytes stimulated in vitro by phytohaemagglutinin, concanavalin A and pokeweed mitogen, a recognized test of cellular immunocompetence. Lymphocytes were cultured in flat-bottomed 96-well microplates at 37 degrees C for 96 h (phytohaemagglutinin and concanavalin A) or 144 h (pokeweed mitogen) in the presence of one mitogen at different concentrations and of one acid added at doses of 1.0, 2.5 or 5.0 mM. Cell blastogenesis was measured by the incorporation of tritiated thymidine into cellular DNA and compared with that of identical cultures with no acid added (controls). A consistent and progressive inhibitory effect of propionic acid with increasing concentrations in culture was identified with all mitogens and was more pronounced with pokeweed mitogen. Lymphocyte blastogenesis was not altered in the presence of methylmalonic acid. The effect of propionate was observed only when the drug was added at the beginning (phytohaemagglutinin-activated) or until 24 h (concanavalin A- and pokeweed mitogen-activated) of culture. The viability of lymphocytes after treatment with the drug, as assessed by the Trypan Blue exclusion test, revealed no change when compared with the same untreated lymphocytes, indicating no lymphocytotoxic activity. In conclusion, propionic acid, which accumulates in tissues of patients with propionic acidaemia, causes 'in vitro' immunosuppression, which may be related to the recurrent infections characteristic of these patients.

Massive hemoptysis in Takayasu's arteritis during pregnancy

Takayasu's arteritis is an uncommon condition affecting predominantly young women. Because the disorder affects women in childbearing age, it may be recognized the first time during pregnancy. Various cardiovascular events may occur in the perinatal period. We describe a patient with Takayasu's arteritis who presented with massive hemoptysis. To our knowledge, this manifestation has not been documented previously.

Lung cancer in the young

Lung cancer is uncommon in individuals age 40 or less. We reviewed the Cancer Registry files of the Ben Taub General Hospital (Houston, TX) from 1971 to 1989 and identified 1678 patients with a documented diagnosis of lung cancer. Among these 1678 patients, 50 (2.98%) were age 40 or less. Thirty-five (70%) of the 50 patients were men and 15 (30%) were women. Their median age was 37 (range of 24 to 40). A smoking history was available in 37 patients. Thirty-five (94.5%) of the 37 patients who were smokers had a > 20-pack per year history of smoking. Four patients were intravenous drug abusers, and one of these four tested positive for the immunodeficiency virus. Twenty-seven (54%) had adenocarcinoma, eight (16%) had squamous cell carcinoma, and six (12%) had other nondescript, nonsmall-cell carcinoma types. In contrast, the proportion of adenocarcinoma for the (all-age) group of 1678 patients with lung cancer was 28.2%. This difference in the proportion of adenocarcinoma between the two age groups was statistically significant (Pearson's Chi 2, 13.7039, p < 0.0005). Thirty-one (77.5%) of the 50 patients had unresectable disease at diagnosis (12 had stage IIIb and 19 had stage IV). The median survival from diagnosis was 26 weeks. These findings suggest that (1) smoking is an important risk factor for this subset of young patients, (2) the proportion of adenocarcinoma is higher in the young compared with the entire group of lung cancer patients, which included patients of all ages, and (3) young patients tend to present with advanced disease at diagnosis, resulting in an extremely poor survival.

Bioequivalence assessment of diltiazem preparations by means of discriminant analysis of data from solid-phase extraction and liquid chromatography

A solid-phase extraction technique for sample clean-up coupled with a new LC procedure is reported for the assay of diltiazem in plasma. The use of disposable cartridges provides selective extraction and easy automation. A new LC system based on LiChrospher RP 60 Select B columns is described. For routine analysis, the procedure provides a rapid simultaneous clean-up of several samples prior to chromatography and reproducible recoveries over a concentration range of 10-800 ng. The procedure was used to analyse the plasma samples from a bioequivalence study of three commercial diltiazem preparations. The pharmacokinetic parameters in 12 healthy male volunteers were determined and the assessment of bioequivalence was conducted by discriminant analysis.

[Bioavailability of 3 formulations of diltiazem]

The plasma concentration profiles of diltiazem were determined in three series of twelve male volunteers to whom a single doses of 60 mg of diltiazem was administered. Three commercial diltiazem preparations, labelled A, B and C were evaluated. The plasmas were analysed for diltiazem concentration by a new HPLC technique and from the data on concentration profiles, the pharmacokinetic parameters, Cmax, Tmax, T1/2, AUC0-12 and AUC0-infinity were calculated from the function derived by computerized curve fitting and integration. Computerized Pattern Analysis was used for product comparison, based on the plasmatic concentration and the calculated pharmacokinetic data. Differences observed between the three products regarding plasmatic levels and pharmacokinetic, were within the range values defined by individual variation, and were similar to the ones described in the literature for single doses of diltiazem - 60 mg. However, the multiparametric analysis showed that the studied preparations formed two distinct groups: preparation B was different from preparations A and C. This means that preparation B was not bioequivalent to preparations A and C, both considered as bioequivalent.

Erysipelothrix endocarditis with previous cutaneous lesion: report of a case and review of the literature

This report describes the first documented case of Erysipelothrix rhusiopathiae endocarditis in Latin America. The patient was a 51-years-old male, moderate alcoholic, with a previous history of aortic failure. He was used to fishing and cooking as a hobby and had his left hand wounded by a fish-bone. The disease began with erysipeloid form and developed to septicemia and endocarditis. He was treated with antibiotics and surgery for aortic valve replacement. There are only 46 cases of E. rhusiopathiae endocarditis reported to date. The authors wonder if several other cases might go unreported for lack of microbiological laboratorial diagnosis.