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Biomedical subjects

B L Zhang

Publications and source records attributed to B L Zhang.

At least 19 recordsLinked to original sources
PubMed2005

Central actions of agmatine in conscious spontaneously hypertensive rats.

Agmatine (decarboxylated arginine) is an endogenous ligand at alpha-2 adrenergic and imidazoline nonadrenergic receptors. In conscious spontaneously hypertensive rats (SHRs), we have studied its central effects on cardiovascular function and its interaction with the second generation centrally acting antihypertensive agent, rilmenidine, and the reference imidazoline, clonidine, which are mixed alpha-2 adrenoceptor/imidazoline receptor agonists. Agmatine, when administered in low doses (30-100 microg/kg) into the fourth ventricle had no effect on blood pressure and caused an increase in heart rate. A higher dose of 1,000 microg/kg produced an adverse reaction in conscious SHRs and a marked and long-lasting increase in blood pressure. The effects of fourth ventricular rilmenidine (300 microg/kg) and clonidine (10 microg/kg) were equihypotensive and equibradycardic. The antihypertensive and bradycardic effects of rilmenidine were not reversed by cumulative intracisternal doses (30-100-300 microg/kg) of agmatine. The bradycardia obtained 20 min after intracisternal administration of clonidine in the fourth ventricle was reversed by 30 microg/kg agmatine. Only the highest dose of agmatine (1,000 microg/kg) did reverse the antihypertensive effects of rilmenidine and clonidine. Agmatine neither did mimic nor block the antihypertensive response to rilmenidine and clonidine at well-tolerated doses. Yet agmatine produced a small tachycardia at relatively low doses and was able to reverse the bradycardia induced by clonidine. Therefore, its affinity for alpha-2 adrenoceptors in vitro might partially explain its cardiovascular effects in vivo.

Agmatine↗
PubMed2004

Continuous light exposure and sympathectomy suppress circadian rhythm of blood pressure in rats.

BACKGROUND: Although the 24-hour rhythm in blood pressure is well known, it is not clear how environmental light controls circadian cardiovascular and behavioral rhythms. METHODS AND RESULTS: The prolonged exposure of Wistar rats to continuous light for 17 weeks, beginning at 5 weeks old, induced a complete suppression of their blood pressure, heart rate, spontaneous locomotor activity, and body temperature circadian rhythms. Daily subcutaneous melatonin injections at the theoretical onset of darkness for 21 days could not restore light-suppressed blood pressure circadian rhythm, whereas it partially synchronized heart rate and body temperature rhythms and it fully restored spontaneous locomotor activity rhythms, as measured by radiotelemetry. The transfer of these rats from constant light to a standard 12:12-hour light/dark photoperiod fully restored circadian rhythmicity within 2 to 5 days, although their 24-hour diastolic blood pressure remained elevated. Synchronized rats were then subjected to superior cervical ganglionectomy (SCGx) and 6-hydroxydopamine sympathectomy (SYMPx). SCGx plus SYMPx completely abolished the circadian rhythm in blood pressure and significantly reduced those in heart rate, spontaneous locomotor activity, and body temperature. CONCLUSIONS: We conclude that in Wistar rats exposed to continuous light, the light-induced increase in sympathetic outflow can suppress blood pressure circadian rhythm, and sustained cardiac wall stress can alter diastolic function at rest. Preserved inotropy in these conditions must result from an adaptative hypertrophic response of myocytes.

Animals↗
PubMed2001

[Effect of head-down bed rest on human EEG].

Objective. To study the influences of short-term simulated weightlessness on human EEG. Method. EEG of 12 male subjects (aged 18-22) was recorded, pre-HDBR (-6 degrees head down bed rest), mid-HDBR (3rd, 4th, 6th day) and post-HDBR (3rd day). Then these EEG recordings were analyzed by power spectral analysis. Result. During HDBR, peak frequency of EEG gradually slowed down (6th day, P<0.05). Alpha-band activities were enhanced (alpha1: P<0.001. Alpha2: 3rd and 6th day, P<0.05; 4th day, P<0.001) and reached maximum on the 4th day. Alpha1/alpha2 ascended (6th day, C3 and C4: p<0.02; F4, P4, T3, T4, T5: P<0.05). Theta-band activities enhanced (P<0.001), and reached maximum on the 3rd day at frontal regions, on the 4th day at parieto-occipital regions. Theta/alpha ascended obviously (6th day, P3, O1: P<0.05). Meanwhile, beta1, activities also enhanced (P<0.001), and reached maximum on the 3rd day at frontal regions. After HDBR, the index that recovered to the pre-HDBR level first was EEG peak frequency. Conclusion. HDBR caused obvious changes of EEG power spectrum characteristic. There exists a potential influence on brain function.

Adolescent↗
PubMed2001

Blood pressure and heart rate determination by radiotelemetry in mice.

Mice are not commonly used in cardiovascular physiology, especially in space physiology because of methodological problems. The initial studies that have monitored arterial pressure and heart rate in mice used the tail cuff plethysmography method or classical catheterization techniques with a catheter liable to an external pressure transducer. But for long term arterial pressure measurements the studies have been facilitated by the development of radiotelemetry. This is a less constraining method as classical one allowing to monitor in continuous in freely moving animal blood pressure, heart rate and temperature. This technique allows to record these parameters thank to an implanted transmitter without physical connection with the monitoring system. The aim of this work was to valid the use of the radiotelemetry in mice to evaluate arterial blood pressure and heart rate during different stress conditions (but only control data are described in this paper).

Animals↗
PubMed2000

Effects of Lu-Duo-Wei capsules on superoxide dismutase activity and contents of malondialdehyde and lipofuscin in the brain of the housefly.

The biochemical actions of Lu-Duo-Wei capsules and tea polyphenol in relation to their antioxidant capability have been compared in the male housefly, Musca domestica. It was found that tea polyphenol had the effect of increasing the activity of superoxide dismutase (SOD) in the brain of the housefly only at the 60th day in the experimental period whereas Lu-Duo-Wei showed more obvious effects on SOD than tea polyphenol irrespective of experimental days. Moreover, the contents of malondialdehyde (MDA) and the rate of lipofuscin accumulation were decreased by the effect of Lu-Duo-Wei at the 20th, 40th, 50th and 60th days, while the similar effect of tea polyphenol on the content of MDA and lipofuscin was observed only at the 40th day. These results indicated that the biochemical actions of Lu-Duo-Wei in antiaging was much stronger than those of tea polyphenol, the mechanism of which was probably related to the synergistic effect of its involved antioxidants and others as well as the exclusive promotion of SOD biosynthesis/or a reduction of free radical-induced damage of the enzyme.

Analysis of Variance↗
PubMed2000

Effects of photoperiod reduction on rat circadian rhythms of BP, heart rate, and locomotor activity.

The effects of a photoperiod reduction in the entrainment of circadian rhythms of systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), and spontaneous locomotor activity (SLA) were determined in conscious Wistar rats by using radiotelemetry. Two groups of seven rats were maintained in a 12:12-h light-dark (12L/12D) photoperiod for 11 wk and then placed in a reduced photoperiod of 8:16-h light-dark (8L/16D) by advancing a 4-h darkness or by advancing and delaying a 2-h darkness for 6 wk. Finally, they were resynchronized to 12L/12D. Advancing a 4-h dark phase induced a 1-h advance of acrophase for SBP, DBP, and HR, but not for SLA. The percent rhythm, amplitude, and the 12-h mean values of all parameters were significantly decreased by the photoperiod reduction. When symmetrically advancing and delaying a 2-h dark phase, a 1 h 20 min delay of acrophases and a decrease in percent rhythms and amplitudes of SBP, DBP, HR, and SLA were observed. Only the 12-h mean values of HR and SLA were decreased. Our findings show that the cardiovascular parameters differ from SLA in phase-shift response to photoperiod reduction and that the adjustment of circadian rhythms to change from 12L/12D to 8L/16D photoperiod depends on the direction of the extension of the dark period.

Animals↗
PubMed2000

[Responses induced by dopamine in Xenopus laevis oocytes injected with mRNA from heat injured rat striatum].

Poly(A)(+) mRNA isolated from the striatum of normal rats and heat injured rats by RNAgents Total RNA Isolation System and PolyTract mRNA RNAgents Isolation Systems was microinjected into Xenopus laevis oocytes to express functional neurotransmitter receptors. Membrane currents were recorded by the conventional patch clamp technique for measuring the relative amounts of mRNA encoding dopamine receptor in order to study the change in dopamine receptors in heat injured rat striatum. There was no change in resting membrane potentials of the oocytes before and after mRNA injection. Dopamine induced membrane currents were shown to be mediated through Cl( ). The oocytes injected with mRNA from heat injured rat striatum were less sensitive to dopamine than those injected with mRNA from normal rats ( P<0.05). The above result showed that heat injury affected gene expression and signal transduction of dopamine receptors in rat striatum.

Animals↗
PubMed1999

Biomedical study on combined effects of simulated weightlessness and emergent depressurization of spacecraft.

Cabin emergent depressurization (CED) may occur in spacecraft during manned space flight. The purpose of this paper was to study the combined effects of simulated weightlessness (SW) and CED factors on humans and animals. It was found that the amplitude of T wave of human electrocardiograms (ECG) significantly decreased in bed rest and hypoxia compared with the control condition (P<0.05), and that suspension with pure O2 induced severer edema in the lungs of rats than that in only a pure O2 environment. SW and pure O2 caused middle ear congestion and decreased the barofunction during pressure changes. These results indicate that human response to CED factors become more serious under SW because of the blood redistribution.

Aerospace Medicine↗
PubMed1999

Effects of lu-duo-wei capsule on prolonging life span of housefly and Drosophila melanogaster.

Lu-Duo-Wei capsule is a product of Chinese medicine having high efficacy in scavenging superoxide and hydroxyl radicals. It contains antioxidants, which may increase longevity, but whether Lu-Duo-Wei capsule has such an effect is unknown. In this study, supplementing the basic diet with Lu-Duo-Wei resulted in prolonging the life span of houseflies and fruit flies. Moreover, the effect of prolonging the life span of houseflies by Lu-Duo-Wei was significantly higher than that of tea polyphenol. The result not only confirms our previous report but also supports the free radical theory of aging.

Animals↗
PubMed1999

[Counteracting effect of hypoxia and Qigong on cardiac rhythm during orthostatic test post simulated weightlessness].

OBJECTIVE: To try to find a new method for countermeasuring the effect of simulated weightlessness. METHODS: The study was carried out in fifteen male healthy subjects, 19-22 years, -6 degrees head-down bed rest (-6 degrees HDBR) for 21 d was used as a weightlessness simulation model. The subjects were divided into three groups: control group (-6 degrees HDBR), hypoxia group (-6 degrees HDBR + inhalation of hypoxic gas mixture two times a day, 20 min each time) and Qigong group (-6 degrees HDBR + Qigong, three times per day, 45 min each time). Orthostatic test (+75 degrees 20 min) was conducted on each subject pre- and post-HDBR. RESULTS: Cardiac rhythm during the orthostatic test was normal pre-HDBR but sinus cardiac arrhythmias were observed in two subjects of the control group and nodal cardiac arrhythmias were observed in two subjects in Qigong group after HDBR. No cardiac arrhythmia was found in hypoxia group. CONCLUSION: Hypoxia is more effective in countermeasuring orthostatic intolerance after weightlessness than Qigong.

Adult↗
PubMed1999

[Study on testing method of susceptibility to decompression sickness in aerospace].

Objective. To provide related parameters for astronauts. Method. A study of susceptibility to decompression sickness was carried out in 43 subjects in a hypobaric chamber. Result. Incidence of altitude decompression sickness under rest condition was closely related to age, time of oxygen prebreathing, gas bubble formation rates in the venous blood flow returned to heart and some other physiological indexes. Incidence of decompression sickness was significantly higher in subjects aged 30-36 years than in those aged 19-20 years under the same experimental conditions. In the older subjects body-fat, blood cholesterole and noradrenaline in urine during experiment were significantly higher than those in the younger subjects. It also showed that among persons of the same ages, when prebreathing time was longer, the incidence of decompression sickness was significantly lower under the same experimental conditions. Conclusion. It is desirable that the susceptibility to decompression in astronaut be tested with 1 h oxygen prebreathing before exposure to the altitude of 10000 m for 30 min.

Adult↗
PubMed1998

Effects of neonatal focal cerebral hypoxia-ischemia on sleep-waking pattern, ECoG power spectra and locomotor activity in the adult rat.

The aim of this study was to determine the influence of neonatal focal cerebral hypoxia-ischemia (HI) on sleep-waking pattern, electrocorticogram (ECoG) power spectra and locomotor activity (LA) in adult Wistar rats. Seven-day old pups were subjected to permanent unilateral ligation of the common carotid artery and transient hypoxia (8% O2). At 10 weeks of age, the extent of brain damages was evaluated by magnetic resonance imaging (MRI) and homogenous injured animals were selected before chronic implantation of radiotelemetry device. Using a single ECoG recording channel method, waking (W), paradoxical sleep (PS) and slow wave sleep (SWS) were continuously recorded for 72 h and they were semi-automatically analyzed off-line. We observed that neonatal HI triggers a cascade of events leading, in adult rats, to brain dysfunction characterized by an increase in SWS (55.0 vs. 40.2% in sham-operated rats, p<0.05) and a marked decrease in W phases duration (43.4 vs. 51.5%, p<0.05) while PS was almost suppressed in HI rats (1.6 vs. 8.3%, p<0.05). In addition, power spectral analysis of ECoG revealed significant (p<0.05) alteration in PS power density with a shift of the dominant frequency peak (5.0 to 7.5 Hz for HI and sham-operated rats, respectively). During the light period, we found that HI induced a pronounced reduction of LA (-30%, p<0.05). These results indicate that Wistar rats exposed to a neonatal unilateral cerebral HI present significant ECoG activity, sleep-waking pattern and behavioral disturbances when adults. However, it remains to establish whether such alterations can be prevented by neuroprotective agents.

Animals↗
PubMed1998

Influence of neonatal focal cerebral hypoxia-ischemia on cardiovascular and neurobehavioral functions in adult Wistar rats.

No experimental studies looked at the disturbances appearing after a neonatal focal cerebral hypoxia-ischemia (HI) when animals become adults. Using radiotelemetry, we examined the effects of neonatal focal cerebral HI on blood pressure (BP), heart rate (HR), locomotor activity (LA), body temperature (BT) levels and circadian rhythm parameters of unrestrained adult Wistar rats. At 15 weeks of age, we continuously recorded the cardiovascular and neurobehavioral parameters of HI (n = 6) and sham-operated (n = 6) rats. In adult rats, HI induced persistent hypertensive effects associated with alteration in BP circadian rhythms and pronounced decreases in mesor and percent rhythm of LA. HR and BT parameters were not significantly modified. Therefore, our results suggest that the rat cardiovascular and behavioural circadian control systems may involve several structures which present selective vulnerability to early cerebral HI.

Animals↗
PubMed1996

Transforming growth factor beta 1: three-dimensional structure in solution and comparison with the X-ray structure of transforming growth factor beta 2.

The three-dimensional solution structure of human transforming growth factor beta 1 (TGF-beta 1) has been determined using multinuclear magnetic resonance spectroscopy and a hybrid distance geometry/ simulated annealing algorithm. It represents one of the first examples of a mammalian protein structure that has been solved by isotopic labeling of the protein in a eukaryotic cell line and multinuclear NMR spectroscopy. The solution structure of the 25 kDa disulfide-linked TGF-beta 1 homodimer was calculated from over 3200 distance and dihedral angle restraints. The final ensemble of 33 accepted structures had no NOE or dihedral angle violations greater than 0.30 A and 5.0 degrees, respectively. The RMSD of backbone atoms for the ensemble of 33 structures relative to their mean structure was 1.1 A when all residues were used in the alignment and 0.7 A when loop regions were omitted. The solution structure of TGF-beta 1 follows two independently determined crystal structures of TGF-beta 2 (Daopin et al., 1992, 1993; Schlunegger & Grütter, 1992, 1993), providing the first opportunity to examine structural differences between the two isoforms at the molecular level. Although the structures are very similar, with an RMSD in backbone atom positions of 1.4 A when loop regions are omitted in the alignment and 1.9 A when all residues are considered, there are several notable differences in structure and flexibility which may be related to function. The clearest example of these is in the beta-turn from residues 69-72: the turn type found in the solution structure of TGF-beta 1 falls into the category of type II, whereas that present in the X-ray crystal structure of TGF-beta 2 is more consistent with a type I turn conformation. This may be of functional significance as studies using TGF-beta chimeras and deletion mutants indicate that this portion of the molecule may be important in receptor binding.

Amides↗
PubMed1996

Antihypertensive effect of thymectomy in Lyon hypertensive rats. Vascular reactivity, renal histology, and sodium excretion.

The aim of this study was to search for the possible mechanisms involved in the antihypertensive effect of neonatal thymectomy that we previously observed in Lyon hypertensive (LH) rats. To that end, we studied in LH and normotensive control (LN) rats the consequences of neonatal thymectomy on vascular reactivity, renal structure, and pressure-natriuresis. The increase in pressor responses to angiotensin I and phenylephrine noted in LH rats as compared to LN animals was abolished by neonatal thymectomy. Histological study showed that kidneys from LH rats exhibited arterial wall hypertrophy, segmental hyalinization of the glomeruli, and were infiltrated by mononuclear cells. All these features of kidney injury were reduced in neonatally thymectomized LH rats. Lastly, the responses of isolated perfused kidneys from LH rats to stepwise reductions in renal perfusion pressure differed from those of LN rats by decreased renal perfusion flow and natriuresis. Neonatal thymectomy tended to improve sodium excretion in parallel with a slight decrease in renal vascular resistances. It is concluded that the normalization of vascular responsiveness to vasoconstrictor factors, the alleviation of renal lesions and, to a lesser extent, the moderate improvement of pressure natriuresis may account, at least in part, for the antihypertensive effect of neonatal thymectomy in LH rats.

Animals↗
PubMed1996

Interactions between nitric oxide and prostanoids in isolated perfused kidneys of the rat.

1. The present study was aimed to assess the interaction between nitric oxide (NO) and thromboxane (Tx) A2-prostaglandin (PG) H2 in single-pass perfused isolated kidneys of the rat. 2. Noradrenaline (NA, 63 and 110 nM) dose-dependently elevated the renal vascular resistance (RVR), the glomerular filtration rate (GFR) and the urinary excretion of sodium (UNa V). Infusion of N omega-nitro-L-arginine methyl ester (L-NAME, 100 microM), an inhibitor of NO synthesis, enhanced the effects of NA on RVR and on UNa V, but decreased those on GFR. The TxA2-PGH2 (TP) receptor blockade by GR32191B (10 microM) attenuated this potentiating effect of L-NAME. 3. When renal perfusion pressure was stepwise increased from 90 to 150 mmHg, L-NAME similarly decreased renal perfusion flow rate and GFR. 4. The venous excretion of TxB2 and 6-keto-PGF1 alpha was increased by L-NAME in baseline conditions as well as after NA or increasing renal perfusion pressure (RPP). 5. These results suggest that: (1) TxA2 and PGH2 play an important role in the overall effect of the renal prostanoids, (2) NO strongly interacts with the cyclo-oxygenase pathway and reduces the prostanoid synthesis in the kidney, and (3) the pressor effect of L-NAME partly relies upon the vasoconstrictor effect of TxA2 and PGH2.

6-Ketoprostaglandin F1 alpha↗
PubMed1996

Learning multiple causes by competition enhanced least mean square error reconstruction.

In this paper we studied a self-organization principle that input should be best reconstructed from a factorial distributed hidden representation, which has been addressed in the literature recently. An auto-encoder network is trained by the Least Mean Square Error Reconstruction (LMSER) while the redundance in the representation is reduced by a proposed anti-Hebbian scheme, in which a penalty term called Receptive Field Overlapping Index (RFOI) is combined into the objective function for enhancing competition among nodes in the network. Our learning scheme provides a way for balancing the cooperation and competition necessary for the self-organization process thus realizes the multiple causes model, which accounts for an observed data by combining assertions from the discovered causes or features in the data. Our experiment results demonstrate again the powerful information processing capability inherent to the popular weighted sum followed by sigmoid squashing. Comparing with previous probability theory based multiple causes models, our scheme is much easier to implement and quite reliable.

Algorithms↗