Biomedical subjects

B Tian

Publications and source records attributed to B Tian.

At least 73 records · Page 4Linked to original sources

PubMed1997

Serial and parallel processing in rhesus monkey auditory cortex.

Auditory cortex on the exposed supratemporal plane in four anesthetized rhesus monkeys was mapped electrophysiologically with both pure-tone (PT) and broad-band complex sounds. The mapping confirmed the existence of at least three tonotopic areas. Primary auditory cortex, AI, was then aspirated, and the remainder of the cortex on the supratemporal plane was remapped. PT-responses in the caudomedial area, CM, were abolished in all animals but one, in which they were restricted to the high-frequency range. Some CM sites were still responsive to complex stimuli. In contrast to the effects on CM, no significant changes were detectable in the rostral area, R. After mapping cortex in four additional monkeys, injections were made with different tracers into matched best-frequency regions of AI, R, and CM. Injections in AI and R led to retrograde labeling of neurons in all three subdivisions of the medial geniculate (MG) nucleus (MGv, MGd, and MGm), as well as nuclei outside MG, whereas CM injections led to only sparse labeling of neurons in a restricted zone of the lateral MGd and, possibly, MGm, in addition to labeling in non-MG sites. The combined results suggest that MGv sends direct projections in parallel to areas AI and R, which drive PT-responses in both areas. PT-responses in area CM, however, appear to be driven by input relayed serially from AI. The direct input to CM from MGd and other thalamic nuclei may thus be capable of mediating responses only to broad-band sounds.

Acoustic Stimulation↗

PubMed1997

Effects of adenosine agonists on intraocular pressure and aqueous humor dynamics in cynomolgus monkeys.

The effects of single or multiple topical doses of the relatively selective A1 adenosine receptor agonists (R)-phenylisopropyladenosine (R-PIA) and N6-cyclohexyladenosine (CHA) on intraocular pressure (IOP), aqueous humor flow (AHF) and outflow facility were investigated in ocular normotensive cynomolgus monkeys. IOP and AHF were determined, under ketamine anesthesia, by Goldmann applanation tonometry and fluorophotometry, respectively. Total outflow facility was determined by anterior chamber perfusion under pentobarbital anesthesia. A single unilateral topical application of R-PIA (20-250 micrograms) or CHA (20-500 micrograms) produced ocular hypertension (maximum rise = 4.9 or 3.5 mmHg) within 30 min, followed by ocular hypotension (maximum fall = 2.1 or 3.6 mmHg) from 2-6 hr. The relatively selective adenosine A2 antagonist 3,7-dimethyl-1-propargylxanthine (DMPX, 320 micrograms) inhibited the early hypertension, without influencing the hypotension. Neither 100 micrograms R-PIA nor 500 micrograms CHA clearly altered AHF. Total outflow facility was increased by 71% 3 hr after 100 micrograms R-PIA. In conclusion, the early ocular hypertension produced by topical adenosine agonists in cynomolgus monkeys is associated with the activation of adenosine A2 receptors, while the subsequent hypotension appears to be mediated by adenosine A1 receptors and results primarily from increased outflow facility.

Adenosine↗

PubMed1997

Delayed reperfusion alters matrix metalloproteinase activity and fibronectin mRNA expression in the infarct zone of the ligated rat heart.

Delayed reperfusion has a beneficial effect on prognosis, independent of infarct size. One potential mechanism to explain this observation may be an effect on infarct healing. In this study, the impact of delayed reperfusion on two aspects of the healing process was examined, the activity of matrix metalloproteinase (MMP) enzymes and the expression of fibronectin (FN) mRNA. The rat model of coronary artery ligation was used and rats were randomly assigned to delayed reperfusion (150 min following coronary ligation) or permanent ligation. Animals were subsequently killed 1, 2, 3 and 7 days following infarction. Infarct tissue was harvested for MMP activity (zymography), FN mRNA (RNase protection analysis) and protein (immunofluorescence microscopy and Western analysis), and collagen content (hydroxyproline concentration). Infarction produced marked activation of MMP-1, -2, and -9. Reperfusion significantly attenuated the activity of these enzymes (approximately 50% reduction in MMP-1, P=0.03 and ;60% reduction in MMP-2 at 7 days, P=0.001; approximately 55% reduction in MMP-9 at 24 h and 84% reduction at 48 h, P=0.01 and 0.002, respectively). Delayed reperfusion also produced a trend toward a greater increase in FN mRNA 24 h following infarction and immunofluorescent staining suggested the presence of more FN protein at this point. These data demonstrate that delayed reperfusion alters matrix metalloproteinase activity and fibronectin mRNA expression in the infarct zone. The impact of these changes on infarct healing and their association with the improved prognosis of a patent infarct vessel following infarction will require further study.

Animals↗

PubMed1997

Echolocation signals of the greater horseshoe bat (Rhinolophus ferrumequinum) in transfer flight and during landing.

Echolocation signals of horseshoe bats (Rhinolophidae) consist of a relatively long component of constant frequency (CF) which is preceded by an initial frequency-modulated (iFM) component and followed by a terminal frequency-modulated (tFM) component. To examine the role of these components in echolocation, four bats were trained to fly from a perch to a landing bar. A dual camera system allowed reconstruction of the flight paths in three dimensions. Echolocation signals were recorded, analyzed, and correlated with the flight behavior of the bats. It was confirmed that during flight the bats compensate the Doppler shifts which are produced by their own flight movement. In free flight they emit per wing beat one single signal of long duration, with little variation in the three signal components. In approach flight the bats reduce pulse duration and interval with decreasing target range. The iFM is not varied with respect to target range, suggesting that this component plays little role in the processing of echolocating a target of interest. The bandwidth of the tFM component is increased while its duration is shortened in proportion to decreasing target range, so that the signal-echo overlap of the FM component is avoided down to a target distance of 15 cm. These concurrent changes suggest that the tFM component is used for ranging. During the last 60 cm of the approach the bats compensated for the increase of echo SPL by lowering the emission level of the CF component by 6-9 dB and that of the tFM component by 9-11 dB per halving of range. The specific signal structure of horseshoe bats is discussed as an adaptation for the hunting of fluttering insects in highly cluttered environments.

Animals↗

PubMed1997

Blood pressures and cardiovascular homeostasis in mice having reduced or absent angiotensin-converting enzyme gene function.

We studied cardiovascular phenotypes in wild-type (+/+), heterozygous (+/-), and homozygous mutant (-/-) mice for an insertional inactivation of the angiotensin-converting enzyme (ACE) gene (Ace in mice, ACE in humans). Compared with +/+ mice, baseline mean arterial pressure was not significantly altered in +/- mice but was reduced by 51+/-4 mm Hg in -/- mice. Although the pressor response to injected angiotensin II did not differ significantly in the three genotypic groups, the pressor response to angiotensin I was strongly affected by Ace genotype: Compared with the response in the +/+ group (+26% of baseline), the response to Ang I was close to half normal (+12%) in the +/- group and virtually abolished (+1%) in the -/- group. The depressor response to injected bradykinin was significantly enhanced in the +/- and -/- groups compared with the +/+ group. Ace expression and ACE activity were directly related to functional Ace copy number, and renin and angiotensinogen mRNA levels were inversely related to Ace copy number. Angiotensin type 1A receptor mRNA levels were not significantly different in the +/+, +/-, and -/- groups. We conclude that (1) ACE is essential for the maintenance of normal blood pressure; (2) subnormal levels of ACE affect the blood pressure responses to infused angiotensin I and bradykinin in vivo; and (3) compensations for inactivation of one Ace copy, which include increased expression of renin, normalize blood pressure in heterozygotes.

Analysis of Variance↗

PubMed1997

[Sonographic measures of the hip joint of 1328 newborns of Han and Uygur nationalities-relative factors of congenital dislocation of hip].

The four sonographic methods (Engesaeter, Terjesen, Graf, Morin-Harcke) were used for examining the hip joint of 1328 newborns of Han and Uygur nationalities. The difference between Han and Uygur newborns was not statistical significant, but some literatures reported that in our country, the incidence of different nationalities in different regions varied. Our conclusion is that there is no obvious relationship between the depth of the acetabulum and the percentage of the femoral head covered by the acetabulum. It is caused by other factors, inherent or acquired. The value of the hip joint of the male and female has significant difference (P < 0.0005). The incidence of CDH in girls is much higher than that in boys. This may be related to the different depth of the acetabulum and different percentage of the femoral head covered by the acetabulum. In the period of newborn, girl's depth of the acetabulum is smaller than that of boys.

Anthropometry↗

PubMed1997

[Different susceptibilities to desensitization of three alpha 1-adrenoceptor subtypes induced by sustained norepinephrine stimulation].

cDNAs for the bovine alpha 1A-, hamster alpha 1B- and rat alpha 1D-adrenoceptors (AR) were transfected into human embryonic kidney 293 (HEK293) cells by calcium phosphate precipitation and stably expressed at high levels. The inositol phosphates (InsPs) accumulation was measured by the method of 3H-inositol incorporation and column chromatography. Susceptibilities to the desensitization of alpha 1-AR subtypes-mediated InsPs accumulation were determined in HEK 293 cells stimulated sustainedly by norepinephrine (NE). The NE-induced InsPs accumulation showed progressive decrease by NE pretreatment with increasing time of preincubation and concentration of NE in the cells transfected with all the alpha 1-AR subtypes. However, susceptibilities to the desensitization were different among the three subtypes. The desensitization of alpha 1A-AR took place earliest and needed lowest concentration of NE. The desensitization of alpha 1D-AR appeared to be the latest and needed hightest concentration of NE, while alpha 1B-AR stood in between.

Adrenergic alpha-Agonists↗

PubMed1996

[Alteration of cardiac alpha 1-adrenergic receptor subtypes in cardiac insufficient rat].

The cardiac insufficiency was produced by simultaneous constriction of abdominal aortae and renal artery in rat. Radioligand binding and reverse transcription-polymerase chain reaction (RT-PCR) were used respectively to determine the alterations of cardiac alpha 1-adrenergic receptor (alpha 1-AR) subtypes at protein level and gene transcription level. The Scatchard analysis of 125I-BE 2254 saturation curves showed that in cardiac insufficient rat hearts the KD values (229 +/- 32 vs 195 +/- 15 pmol/L) and the Bmax values (102 +/- 12 vs 96 +/- 17 fmol/mg) were not significantly different from those of control hearts. In the insufficient rat hearts, the inhibition of alpha 1-AR specific binding by WB 4101 showed that the high affinity sites (alpha 1A + alpha 1D) were increased from the 22 +/- 5% of the control to 51 +/- 7% (P < 0.01). The alpha 1A-AR mRNA level was increased, alpha 1B-AR mRNA level decreased while alpha 1D-AR unchanged. The results suggest that in cardiac insufficient rat hearts the subtype composition is altered as shown by increased alpha 1A-AR, decreased alpha 1B-AR and unchanged alpha 1D-AR, although the total amount of alpha 1-AR is unchanged.

Animals↗

PubMed1995

Processing of complex sounds in the macaque nonprimary auditory cortex.

Neurons in the superior temporal gyrus of anesthetized rhesus monkeys were exposed to complex acoustic stimuli. Bandpassed noise bursts with defined center frequencies evoked responses that were greatly enhanced over those evoked by pure tones. This finding led to the discovery of at least one new cochleotopic area in the lateral belt of the nonprimary auditory cortex. The best center frequencies of neurons varied along a rostrocaudal axis, and the best bandwidths of the noise bursts varied along a mediolateral axis. When digitized monkey calls were used as stimuli, many neurons showed a preference for some calls over others. Manipulation of the calls' frequency structure and playback of separate components revealed different types of spectral integration. The lateral areas of the monkey auditory cortex appear to be part of a hierarchical sequence in which neurons prefer increasingly complex stimuli and may form an important stage in the preprocessing of communication sounds.

Acoustic Stimulation↗

PubMed1995

Chinese squash leaf curl virus: a new whitefly-transmitted geminivirus.

Coat protein (CP) gene of the Chinese squash leaf curl virus (SqLCV-C) was amplified through PCR, cloned and completely sequenced. Based on the comparisons at the levels of both CP gene nucleotide and CP-deduced amino acid sequences with other geminiviruses, SqLCV-C is confirmed to be distinct from the American squash leaf curl virus (SqLCV-E). It is a new geminivirus transmitted by whitefly Bemisia tabaci, which infects dicotyledonous plants and is more closely related to the Indian cassava mosaic virus (ICMV).

Amino Acid Sequence↗

PubMed1995

Nucleotide sequence of maize dwarf mosaic virus capsid protein gene and its expression in Escherichia coli.

The 3'-terminal 1,279 nucleotide sequence of maize dwarf mosaic virus (MDMV) genome has been determined. This sequence contains an open reading frame of 1,023 nucleotides and a 3'-non-coding region of 256 nucleotides. The open reading frame includes all of the coding regions for the viral capsid protein (CP) and part of the viral nuclear inclusion protein (NIb). The predicted viral CP consists of 313 amino acid residues with a calculated molecular weight of 35,400. The amino acid sequence of the viral CP derived from MDMV cDNA shows about 47%-54% homology to that of 4 other potyviruses. The viral CP gene was constructed in frame with the lacZ gene in pUC19 plasmid and expressed in E. coli cells. The fusion polypeptide positively reacted in Western blot with an antiserum prepared against the native viral CP.

Amino Acid Sequence↗

PubMed1994

Cardiovascular effects of NMDA and MK-801 infusion at area postrema and mNTS in rat.

In urethane-anesthetized male Sprague-Dawley rats, microinfusion of N-methyl-D-aspartate (NMDA) into the area postrema (AP) at the dose of 10 ng produced significant decreases in mean arterial pressure (MAP) (-26 +/- 5 mmHg), heart rate (HR) (-34 +/- 6 bpm), renal blood flow, mesenteric blood flow, and iliac vascular resistance. In addition, microinfusion of the same dosage of NMDA into the medial nucleus tractus solitarius (mNTS) produced significant decreases in MAP (-33 +/- 4 mmHg), HR (-33 +/- 6 bpm), renal blood flow, mesenteric blood flow and vascular resistance, and iliac blood flow and resistance. MK-801 (dizocilpine) microinfusion alone produced no significant changes in MAP or HR when microinfused either into the AP or unilaterally into the mNTS; however, bilateral microinfusion of MK-801 into mNTS produced sustained hypertension and tachycardia, lasting about 30 min. MK-801 pretreatment at both AP and mNTS effectively blocked NMDA-induced cardiovascular responses. MK-801 microinfusion at AP significantly attenuated baroreceptor reflex-mediated bradycardia elicited by intravenous injection of phenylephrine, but did not alter reflex tachycardia elicited by intravenous nitroprusside. In conclusion, NMDA receptor-mediated neurotransmission is involved in the cardiovascular functions of both AP and mNTS. Both loci appear to be sites of action for MK-801.

Animals↗

PubMed1994

MK-801 affects cardiovascular responses produced by GABAA agents in area postrema.

The cardiovascular effects of nanoliter microinfusions of muscimol, bicuculline, and MK-801 (dizocilpine) into area postrema (AP) were tested in urethane-anesthetized male Sprague-Dawley rats. Microinfusion of muscimol (10 nl/min/5min, 1 ng/nl) into the AP produced significant hypertension (+29 +/- 8 mmHg), but no significant change in heart rate (HR). Microinfusion of bicuculline (10 nl/min/5 min, 1 ng/nl) into the AP produced significant hypotension (-27 +/- 4 mmHg) and bradycardia (-53 +/- 10 bpm). Treatment of the AP with MK-801 (20 nl/min/5 min, 6 ng/nl) produced no changes in mean arterial pressure or HR by itself, but it completely blocked the hypotension and bradycardia produced by bicuculline infusion, without affecting the hypertension produced by muscimol microinfusion into AP. Following pretreatment of AP with MK-801, microinfusion of muscimol into the AP produced significant tachycardia (+51 +/- 16 bpm). The data suggest that a) GABAergic neurotransmission in the AP affects its cardiovascular functions; b) functional interactions between NMDA receptor-mediated neurotransmission and GABAA receptor-mediated neurotransmission within the AP modulate blood pressure and HR regulation.

Animals↗

PubMed1994

Processing of frequency-modulated sounds in the cat's anterior auditory field.

1. Single-neuron activity was recorded from the anterior auditory field (AAF) in the cortex of gas-anesthetized cats. 2. Tone bursts and broad-band complex sounds were used for auditory stimulation. Responses to frequency-modulated (FM) sounds, in particular, were studied systematically. 3. Linear FM sweeps were centered around the best frequency (BF) of a neuron and had an excursion large enough to cover its whole frequency tuning range. Rate and direction of change of the FM sweeps were varied. 4. In 69% of the FM responses, a peak was found at an instantaneous frequency that corresponded to the BF in the pure-tone response. Thirty-three percent of the units had multiple maxima in their FM response. These secondary maxima were not always reflected in the pure-tone response of the same neurons. 5. The vast majority of AAF neurons showed one of two types of selectivity for FM rate. Depending on the criterion, almost half of the cells (46%) preferred fast changes of > 200 Hz/ms (high-pass) in both FM directions. Forty-eight percent of all neurons showed band-pass behavior with a clear preference in the middle range of FM rates in one or both directions. Low-pass or all-pass neurons made up only a small proportion (4 and 1%, respectively) of AAF neurons. 6. When both directions of an FM sweep (low-to-high and high-to-low-frequency) were tested, 66% of the neurons clearly were selective for one direction. This selectivity was not present necessarily at the preferred FM rate. In general, FM direction selectivity was most pronounced at slower FM rates. 7. The selectivity of AAF neurons for the rate and direction of FM sounds makes these neurons suitable for the detection and analysis of communication sounds, which often contain FM components with a particular sweep rate and direction.

Animals↗

PubMed1994

[A primary evaluation of VAS for use in clinical experimental pain assessment].

The visual analogue scale (VAS) is a commonly used method for pain measurement abroad, though its clinical use has not been reported in our country. Fifty patients, who had received lower abdomen and lower extremities stimulation, were studied. Pain was induced by hand needle and electric needle stimulation. The data demonstrated that VAS is reliable and precise, that electric needle stimulation is more sensitive than hand needle stimulation, and that the factors of age, profession and education level affect the measured value of pain.

Adolescent↗

PubMed1994

[Role of cardiac renin-angiotensin system in swimming induced physiological myocardial hypertrophy].

To determine the contribution of cardiac renin-angiotensin system (RAS) to the physiological myocardial hypertrophy induced by swimming training and the relationship between locally produced and circulating RAS, both ventricular and plasma angiotensin (Ang) I and II contents, ventricular angiotensin converting enzyme (ACE) and plasma renin activity (PRA) were detected by means of radioimmunoassay and biochemical method. It was shown that after 5 weeks of swimming, the ventricular wet weight to body weight ratio (V/Bwt) and Ang II in both left and right ventricles and ACE activity increased markedly as compared with the controls (P < 0.05). Furthermore, significantly positive correlation was found between the ventricular Ang II and V/Bwt (r = 0.7721, P < 0.001), while the plasma Ang I and II and PRA remained at the control level. No correlation was found between plasma Ang II and V/Bwt. These above findings suggest that cardiac RAS may play an important role in physiological myocardial hypertrophy and to a large extent is in dependent on circulating RAS.

Angiotensin II↗

PubMed1994

Expression of human hepatitis B virus surface antigen gene in transgenic tobacco.

Expression of Human hepatitis B virus surface antigen (HBsAg) gene in plant was reported for the first time. The recombinant plasmid pRoKII-HBsAg was constructed by inserting HBsAg gene into the downstream of CaMV 35S promoter of binary vector pRoKII and then introduced into Agrobacterium tumefaciens LBA4404. The kanamycin-resistant plants were obtained by Agrobacterium-mediated transformation system. It was shown that HBsAg gene was expressed in transgenic tobacco plants and their progenies by ELISA. The spherical particles of psi 22 nm is the leaf extract of transgenic tobacco were observed by immunosorbent electron microscopy.

Gene Expression↗

PubMed1993

Mercury-free disposable lead sensors based on potentiometric stripping analysis at gold-coated screen-printed electrodes.

Gold-coated screen-printed electrodes offer reliable quantitation of trace lead in connection with potentiometric stripping analysis (PSA). Such replacement of mercury-based sensors, with gold-coated ones, avoids environmental contamination associated with the disposal of mercury electrodes in connection with large-scale screening for lead poisoning. The PSA operation obviates the need for oxygen removal, offers low background contributions, and minimizes surfactant interferences. Changes in the peak intensity and position (vs mercury-coated strips) offer new selectivity dimensions. Various experimental parameters are optimized to allow convenient monitoring of micrograms per liter lead concentrations following short deposition periods. Applicability to urine and drinking water samples is illustrated. The highly stable response of these screen-printed electrodes makes them very attractive for both single-use and multiple applications.

Disposable Equipment↗