Biomedical subjects

Y Zhou

Publications and source records attributed to Y Zhou.

At least 973 records · Page 54Linked to original sources

PubMedDate not supplied

Mechanism of testicular atrophy induced by di-n-butyl phthalate in rats. Part 4. Changes in the activity of succinate dehydrogenase and the levels of transferrin and ferritin in the Sertoli and germ cells.

A single oral dose of di-n-butyl phthalate (DBP) to male rats caused a sloughing of the germ cells at 6 h both with a decrease in the activity of succinate dehydrogenase (SDH) in the Sertoli cells and in the Sertoli-germ connection and with an increase in the activity of lactate dehydrogenase (LDH) in the germ cells. Increases in transferrin (Tf) concentrations were observed in the Sertoli cells, Sertoli-germ connection, epididymis-ductus deferens and liver of rats. Decreases in Tf and ferritin (Ft) levels were observed in the seminal vesicle and seminiferous lumen, respectively. An increase in favin adenine dinucleotide (FAD) level was found in the interstitial cells.

Animals↗

PubMedDate not supplied

Measurement of upper airway movement by acoustic reflection.

The acoustic reflection method provides a noninvasive way to determine the airway geometry. Based on a discrete upper airway model, an inverse scheme is developed to infer the upper airway area as a function of distance. We incorporate this scheme into a system that can generate multiple acoustic pulses to sample the upper airway geometry at a maximum frequency of 30 Hz, making possible determination of the airway area-distance relation as a function of time. Therefore, we can monitor the dynamic behavior of the upper airway during breathing. To validate the approach, we visualized vocal cord movements in three normal subjects via laryngoscopy; simultaneously acoustic measurements were made at 10 Hz. Video images of vocal cord movement were recorded and digitized. We compared the laryngeal area from analysis of the video images with the acoustic assessment at the level of the glottis. Linear regression analysis shows that the correlation coefficients are between 0.85 and 0.9 for all three subjects. We conclude that the acoustic reflection method is a useful tool for measuring vocal cord movement without the use of laryngoscopy, and the approach promises to be a useful one to measure the movement of the whole upper airway. This paper also discusses the limitations inherent in the algorithm and some useful procedures to ensure accurate and reliable area computation during implementation.

Acoustics↗

PubMedDate not supplied

Characterization of transforming growth factor-beta 1 gene expression in porcine immune cells.

We have investigated the regulation of transforming growth factor beta 1 gene expression in a variety of porcine immune cell populations, including peripheral blood mononuclear cells (PBMC), peripheral blood monocytes, alveolar macrophages and lymphoid cells from various swine lymphoid tissues. Using porcine transforming growth factor beta 1 cDNA probes in Northern blot assays, messages of 2.5 and 3.5 kb TGF beta 1 mRNA were detected in the cells investigated. A variety of mitogenic and immunomodulatory substances were examined for their ability to induce TGF beta 1 mRNA expression. These include phorbol 12-myristate 13-acetate (PMA), phytohemagglutinin (PHA), concanavalin A (Con A), lipopolysaccharide (LPS), dexamethasone (Dex), tumor necrosis factor (TNF) and interleukin (IL)-1 alpha. While low level constitutive expression of TGF beta 1 mRNA was detected from all cells investigated, PMA treatment of PBMC and alveolar macrophages resulted in a more than 10-fold increase in the steady-state level of TGF beta 1 mRNA within 2 hr of PMA addition. Also, the effect of opiate drugs, methadone (Md) and morphine (Mor), on TGF beta 1 gene expression was determined. Cells treated with opiates expressed the same levels of TGF beta 1 mRNA as untreated cells. Since TGF beta 1 biological activity can be induced by opiates, the regulation of TGF beta 1 gene expression likely involves mechanisms that do not cause changes in mRNA levels.

Animals↗

PubMedDate not supplied

Noxious stimulation accelerated the expression of c-fos protooncogene in cholecystokininergic and dopaminergic neurons in the ventral tegmental area.

Cholecystokininergic (CCK) and dopaminergic systems in the midbrain have been implicated in pain modulation. In the present study, Fos immunoreactivity was used as a marker of neuronal activity to investigate if subcutaneous injection of formalin (a model of noxious stimulation) could activate the CCKergic and dopaminergic neurons in the midbrain. Noxious stimulation increased significantly the numbers of Fos-positive CCKergic and dopaminergic neurons in the ventral tegmental area (VTA), whereas no significant changes in the numbers of Fos-positive CCKergic or dopaminergic neurons were observed in other midbrain nuclei. These results indicate that the VTA may play a role in pain modulation.

Animals↗

PubMedDate not supplied

Reaction time, attention, and impulsivity in epilepsy.

Reaction time, attention, and impulsivity were studied in 112 children with epilepsy (4.5-13 years) using a computerized test. We measured simple reaction time (response with each hand separately to a single stimulus), forced choice reaction time (two stimuli presented in random order, one designated for each hand), and choice reaction time with distraction (two response stimuli, one for each hand, with two additional distracting stimuli randomly inserted). We also measured variability of speed of response and errors of omission and commission. Controls were unaffected children of similar age, ethnic, and socioeconomic backgrounds. Children with epilepsy were significantly slower, more variable, and made more omission errors than control children, even when analysis was limited to epileptic patients with IQ greater than 90, but they did not make more commission (i.e., impulsive) errors. Reaction times were related to IQ, but in general were not related to seizure severity, duration of seizure disorder, or duration of medication use. Untreated patients (N = 13) did not differ from those with antiepileptic drug levels in the therapeutic range on the day of testing (N = 52), but differed significantly from normal patients. Epileptic patients demonstrated significant slowing of reaction time and inattention, but not significant impulsivity, compared to normal children; however, these deficits do not appear to be related specifically to seizure history or treatment.

Adolescent↗

PubMedDate not supplied

A Canadian high-energy neutron spectrometry system for measurements in space.

Bubble Technology Industries Inc. (BTI), with the support of the Canadian Space Agency, has finished the construction of the Canadian High-Energy Neutron Spectrometry System (CHENSS). This spectrometer is intended to measure the high energy neutron spectrum (approximately 1-100 MeV) encountered in spacecraft in low earth orbit. CHENSS is designed to fly aboard a US space shuttle and its scientific results should facilitate the prediction of neutron dose to astronauts in space from readings of different types of radiation dosimeters that are being used in various missions.

Astronauts↗

PubMedDate not supplied

Individual change amid stable smoking patterns in polydrug users over 3 years.

The pattern of stability/change in smoking status was examined annually in 254 community-dwelling polydrug users over 3 years. Respondents' smoking status was classified as nonsmoker, intermittent smoker, or "everyday" smoker. Results showed that the typical probability of retaining the same smoking status across any two consecutive assessments was: 0.77 for nonsmokers (never smokers and former smokers combined), 0.82 for everyday smokers, and 0.16 for intermittent smokers. The transition matrix proved stable across three observations; the predicted equilibrium distribution matched well with observed distributions. Fifty-five percent of intermittent smokers converted to everyday smoking within a year, but 29% converted to former-smoker status in the same period. No other transition exceeded 12%. Considerable flux in individual smoking status, particularly among intermittent smokers, was observed despite stable prevalence of smoking status in this population. Intermittent smoking status appeared to be a temporary "way station" between the two more stable everyday smoker and nonsmoker classifications. Results challenge current assumptions about "occasional" or "chipper" smokers.

Adult↗

PubMedDate not supplied

Adhesive interactions in peri-implantation morphogenesis and placentation.

Antibody perturbation and gene knockout studies show that adhesion receptor modulation plays a critical role in peri-implantation mouse embryo and human cytotrophoblast differentiation. Deletion of beta 1 integrins leads to cell death in the inner cell mass of mouse embryos shortly after implantation in vivo or blastocyst outgrowth in vitro. In F9 embryonal carcinoma cells, deleting beta 1 also affects migration of parietal endoderm even on substrates for which the mutant cells express alternative receptors. Human cytotrophoblasts switch their integrin repertoire as they differentiate and invade the uterine interstitium and vasculature. Interestingly, cytotrophoblasts also transform their cell-cell adhesion molecule phenotype, expressing additional cadherins and immunoglobulin family members as they differentiate. Many of these modulations in adhesion phenotype are initiated early in the pre- and/or peri-implantation periods in human and mouse embryos. Therefore, they constitute important markers of normal progression for evaluating effects of environmental stress and for testing the hypothesis that abnormal switching of adhesion molecules characterizes a significant proportion of conceptuses that fail early in development.

Animals↗

PubMedDate not supplied

Selective depletion of beta cells affects the development of alpha cells in cat retina.

The results of previous studies suggest that class-specific interactions contribute to the development of the different classes of retinal ganglion cells. We tested this hypothesis by examining the morphologies and distributions of alpha (alpha) cells in regions of mature cat retina selectively depleted of beta (beta) cells as a result of visual cortex lesions at birth. We find that alpha cells in regions of central retina depleted of beta cells are abnormally large while alpha cells in regions of peripheral retina depleted of beta cells are abnormally small. The normal central-to-peripheral alpha cell soma-size gradient is absent in hemiretinae depleted of beta cells. The dendritic fields of alpha cells in the border of beta-cell-depleted hemiretina extend preferentially into the beta-cell-poor hemiretina. In spite of this, alpha cell bodies retain their normal retinal distribution and remain distributed in a nonrandom mosaic-like pattern. Thus, it appears that the development of alpha retinal ganglion cells is influenced by interactions both with other alpha cells (class-specific interactions) and with surrounding beta cells (nonclass-specific interactions).

Animals↗

PubMedDate not supplied

Direction-sensitive X and Y cells within the A laminae of the cat's LGNd.

Drifting sinusoidal gratings, moving bars, and moving spots were employed to study the direction sensitivity of 425 neurons in the A laminae of the cat's LGNd. Thirty-two percent of X- and Y-type LGNd relay cells exhibit significant direction sensitivity when tested with drifting sinusoidal gratings. X and Y cells exhibit the same degree of direction sensitivity. Moving spots and bars elicit direction specific responses from LGNd cells that are consistent with those elicited when drifting sinusoidal gratings are employed. For cells that are both orientation and direction sensitive, the preferred direction tends to be orthogonal to the preferred orientation. In general, direction sensitivity is strongest at relatively low spatial frequencies, well below the spatial-frequency cutoff for the cell. The presence of significant numbers of direction-sensitive LGNd cells raises the possibility that subcortical direction specificity is important for the generation of this property in the visual cortex.

Animals↗

PubMedDate not supplied

Stimulus dependence of orientation and direction sensitivity of cat LGNd relay cells without cortical inputs: a comparison with area 17 cells.

The cortical contribution to the orientation and direction sensitivity of LGNd relay cells was investigated by recording the responses of relay cells to drifting sinusoidal gratings of varying spatial frequencies, moving bars, and moving spots in cats in which the visual cortex (areas 17, 18, 19, and LS) was ablated. For comparison, the spatial-frequency dependence of orientation and direction tuning of striate cortical cells was investigated employing the same quantitative techniques used to test LGNd cells. There are no significant differences in the orientation and direction tuning to relay cells in the LGNd of normal and decorticate cats. The orientation and direction sensitivities of cortical cells are dependent on stimulus parameters in a fashion qualitatively similar to that of LGNd cells. The differences in the spatial-frequency bandwidths of LGNd cells and cortical cells may explain many of their differences in orientation and direction tuning. Although factors beyond narrowness of spatial-frequency tuning must exist to account for the much stronger orientation and direction preferences of cells in area 17 when compared to LGNd cells, the evidence suggests that the orientation and direction biases present in the afferents to the visual cortex may contribute to the orientation and direction selectivities found in cortical cells.

Animals↗

PubMedDate not supplied

Adaptation of visually evoked responses of relay cells in the dorsal lateral geniculate nucleus of the cat following prolonged exposure to drifting gratings.

Adaptation of visual cortical cells' responses is observed following repeated presentation of grating stimuli. Grating adaptation is believed to exist only at the cortical level. The purpose of this study was to see if grating adaptation also occurs in the lateral geniculate nucleus. We studied the responses of 164 relay cells in layer A and A1 of the dorsal lateral geniculate nucleus (LGNd) to grating stimuli. Normal cats, as well as cats in which visual cortex was ablated, were studied. Adaptation was investigated using repeated presentation of gratings of different contrasts and orientations. The results showed the following: (1) Grating adaptation reduced the responses of 46% of the LGNd cells recorded. The responses normally decreased within 30 s and then stabilized. However, there was heterogeneity in the effects observed. About 38% of the cells studied were not affected by the adapting gratings. Some cells (16%) showed facilitation rather than habituation of their responses to test stimuli. (2) There was no significant difference between X and Y cells in their susceptibility to adaptation. This suggests that grating adaptation is a general property, independent of cell type. (3) The contrast-response curves of 57% of the LGNd cells studied shifted down after exposure to high-contrast adapting gratings. (4) Adapting gratings of the cells' preferred orientation decreased the orientation sensitivity of 56% of the orientation-sensitive cells. Adapting gratings at the nonpreferred orientation did not affect orientation sensitivity. (5) Prolonged grating adaptation also reduced the responses of 49% of the LGNd cells after inactivation of cortical inputs to the LGNd.

Action Potentials↗

PubMedDate not supplied

Neural correlates of boundary perception.

The responses of neurons in areas V1 (17) and V2 (18) of anesthetized and paralyzed rhesus monkeys and cats were recorded while presenting a set of computer-generated visual stimuli that varied in pattern, texture, luminance, and contrast. We find that a class of extrastriate cortical cells in cats and monkeys can signal the presence of boundaries regardless of the cue or cues that define the boundaries. These cue-invariant (CI) cells were rare in area V1 but easily found in V2. CI cortical cells responded more strongly to more salient boundaries regardless of the cue defining the boundaries. Many CI cortical cells responded to illusory contours and exhibited the same degree of orientation and direction selectivity when tested with boundaries defined by different cues. These cells have significant computational power inherent in their receptive fields since they were able to generalize across stimuli and integrate multiple cues simultaneously in order to signal boundaries. Cells in higher order cortical areas such as MT (Albright, 1992), MST (Geesaman & Anderson, 1996), and IT (Sary et al., 1993) have previously been reported to respond in a cue invariant fashion. The present results suggest that the ability to respond to boundaries in a cue-invariant manner originates at relatively early stages of cortical processing.

Animals↗

PubMedDate not supplied

The signal transduction pathway causing the synergistic hypertrophic effects of neuropeptide Y and norepinephrine on primary cardiomyocyte.

To investigate the synergistic hypertrophic effects of neuropeptide Y (NPY) and norepinephrine (NE) and its possible signal transduction pathway on primary cardiomyocytes, neonatal cardiomyocytes were exposed to NPY, NE or angiotensin II (AnII). All three agonists induced hypertrophic effects, stimulated protein kinase C (PKC) and activated mitogen-activated protein kinase (MAPK). Moreover, NPY at sub-optimal concentration potentiated NE-, not AnII-, induced all of the above effects. Pretreatment with phorbol 12-myristate 13-acetate (PMA) completely abolished these effects for both NE and NPY. NPY potentiation was calcium-independent and pertussis toxin (PTX)-sensitive, and was different from NPY direct hypertrophic effect on cardiomyocyte, as PTX only partially abolished NPY-induced hypertrophic effects. Taken together, NPY participated in the development of cardiac hypertrophy by potentiating NE effects. The signal pathway involves PTX-sensitive G protein, PKC, MAPK, and does not require the presence of calcium.

Adrenergic alpha-Agonists↗

PubMedDate not supplied

Two new iridoid glucosides from Picrorhiza scrophulariiflora.

Two new iridoid glucosides with 3,4-dihydrocatalpol skeleton, piscrosides A (1) and B (2) together with nine known iridoid glucosides and three known cucurbitacin glucosides, were isolated from the stems of Picrorhiza scrophulariiflora. Their structures were established by MS, 1H NMR, 13C NMR and 2D NMR methods (including HSQC, HMBC and NOESY experiments).

Iridoids↗

PubMedDate not supplied

Perioperative management of calves undergoing implantation of a left ventricular assist device.

OBJECTIVE: To describe perioperative management of calves that underwent left lateral thoracotomy, aortic cross-clamping, partial left heart bypass and implantation of a left ventricular assist device. SAMPLE POPULATION: A total of 43 healthy castrated male calves, weighing 121 +/- 24 kg. RESULTS: Diazepam (mean +/- SD, 0.26 +/- 0.07 mg/kg), ketamine (5.9 +/- 2.17 mg/kg) and isoflurane were used in the anesthetic management of calves undergoing implantation of a left ventricular assist device in the descending thoracic aorta. Other adjunctive agents administered were fentanyl (11 +/- 5.4 microg/kg), lidocaine (4.9 +/- 3.19 mg/kg), bupivacaine (0.75%) and butorphanol (0.49 +/- 0.13 mg/kg). None of the calves regurgitated at induction or during intubation. A tube was used to drain the rumen and prevent bloat during the procedure. Partial left heart bypass was used to perfuse the caudal half of the body during the period of aortic cross clamp and device implantation. Initial mean systemic blood pressure was 96 +/- 25 mm Hg, and pressures measured in the auricular artery increased during aortic cross-clamping and bypass. Vasoconstrictor therapy was required to treat caudal arterial hypotension during the procedure in 9 calves. Mean systemic arterial pressures returned to baseline values by the end of the anesthetic period. Initial mean pulmonary arterial pressures (PAP) were 22 +/- 3 mm Hg. A significant but transient increase in pulmonary arterial pressure occurred after both heparin and protamine administration. CONCLUSIONS: The described anesthetic protocol was effective for thoracotomy and implantation of an intra-aortic left ventricular assist device in normal calves. Partial left ventricular bypass was a useful adjunct during the period of aortic cross clamp. The doses of heparin and protamine administered were effective. Responsibility to monitor oxygenation of the cranial half of the animal continues during the bypass period as hypoxemia due to pulmonary dysfunction will not be detected by the perfusionist.

Analysis of Variance↗

PubMedDate not supplied

Cell shape, intracellular pH, and fibroblast growth factor responsiveness during transdifferentiation of retinal pigment epithelium into neuroepithelium in vitro.

In this report we show that some retinal pigment epithelial (RPE) cells, with no expression of neural cell adhesion molecule (N-CAM) (RPEN-CAM-), spontaneously lose pigment and start to express N-CAM in culture. Chick RPE cells normally do not express N-CAM, while the protein is present in chick neural retina. Thus some of the RPE cells in culture started to transdifferentiate into a neuroepithelium (NEN-CAM+). We have measured intracellular pH (pHi) in the RPE cultures and followed its changes in response to basic fibroblast growth factor (bFGF). The depigmented cells protrude above the RPE cell sheet and have a lower resting pHi (approximately 7.05) than the pigmented RPE cells (approximately 7.15). The majority of cells with low resting pHi express N-CAM. The difference in the resting pHi between RPEN-CAM- and NEN-CAM+ cells is not due to the N-CAM expression by NEN-CAM+ cells, as their pHi is the same as the pHi of freshly plated single "round" RPEN-CAM- cells that have not spread yet. NEN-CAM+ cells respond to bFGF with a quick and sustained pHi rise. In contrast, neither the cuboidal RPEN-CAM- cells in a colony centre nor single round RPEN-CAM- cells respond to bFGF with cytoplasmic alkalinization. RPE cells do not proliferate in response to bFGF, while NE cells respond to bFGF with a stimulation of growth. We conclude that bFGF acts not on the fully differentiated RPEN-CAM-, but only on those cells which have already started to transdifferentiate and changed their shape and (or) adhesive status.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Modulation of aortic and cardiac G protein alpha subunits and their mRNAs during norepinephrine infusion in rats.

These studies examine the possibility that alterations in the expression of G protein alpha subunits occur during desensitization of adrenergic responses in the cardiovascular system. To desensitize adrenergic receptors, rats were infused with norepinephrine (NE) subcutaneously (0.1 mg/kg/h) for 3 or 6 days using osmotic minipumps. G protein alpha subunits and their mRNAs were then measured in the aorta and heart using selective antibodies and cDNA probes. Infusion of NE for 6 days significantly decreases the levels of Gs alpha, Gi alpha and Go alpha in the aorta. The mRNAs for the alpha subunits are not altered in the aorta after NE infusion for 3 or 6 days indicating that reduced mRNA expression does not account for the decreased proteins. In the atrium and ventricle the levels of Gs alpha decrease after NE infusion for 3 days but then return to control levels by day 6. The levels of atrial and ventricular Gi alpha are unaltered after NE infusion for 3 days but increase significantly by day 6. Go alpha levels do not change in the atrium or ventricle on either day. The level of Gi2 alpha mRNA increases after NE infusion for 6 days and may account for the increased alpha i protein. The levels of the other G alpha mRNAs do not change in the atrium or ventricle. These results demonstrate that expression of G protein alpha subunits is altered during cardiovascular desensitization, raising the possibility that modulation of the alpha subunits may contribute to reduced adrenergic responsiveness.

Animals↗