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Biomedical subjects

C L Cheng

Publications and source records attributed to C L Cheng.

At least 55 records · Page 3Linked to original sources
PubMed1995

Non-destructive analysis of the protein conformational structure of human pituitary adenomas using reflectance FT-IR microspectroscopy.

Reflectance Fourier-transform infrared microspectroscopy was used to determine the secondary structure and composition of the different human pituitary adenomas. Non-functioning pituitary adenomas exhibited similar protein secondary structure and conformational composition, but active pituitary adenomas revealed different behavior. The differences in secondary structure for the different human pituitary adenomas might possibly be due to the different protein conformations of the proliferated adenoma tissues and various hormones shared.

Adenoma↗
PubMed1995

Effect of capsaicin on micturition and associated reflexes in chronic spinal rats.

The role of capsaicin-sensitive bladder afferents in micturition was studied in unanesthetized chronic spinal rats. Reflex voiding in response to tactile stimulation of the perigenital region appeared 5-9 days after spinal cord injury (SCI) whereas voiding induced by bladder distension occurred 2-3 weeks after SCI. The frequency and amplitude of reflex bladder contractions recorded under isovolumetric conditions were similar in chronic spinal and urethane-anesthetized CNS-intact rats. However, cystometrograms (CMGs) performed 6-8 weeks after SCI revealed that the chronic spinal rats had larger bladder capacities (1.86 ml) than CNS-intact rats (0.48 ml) and also exhibited multiple, small-amplitude, nonvoiding bladder contractions that were not detected in CNS-intact rats. Administration of capsaicin (50 mg/kg s.c.) acutely (onset 14-40 min) suppressed reflex bladder activity induced by bladder distension or by perigenital stimulation in chronic spinal animals. However, pretreatment of chronic spinal rats with capsaicin (125 mg/kg s.c.) 4 days before the experiment did not depress voiding reflexes or change bladder capacity but did eliminate the nonvoiding contractions. Inhibition of reflex bladder contractions by mechanical stimulation of rectoanal canal or the uterine cervix-vagina was not altered by pretreatment with capsaicin. These data indicate that capsaicin-sensitive bladder afferents are not essential for the initiation of reflex micturition in chronic spinal rats. However, these afferents do contribute to hyperactivity of the bladder during the filling phase of the CMG. Thus, capsaicin-sensitive bladder afferents should be evaluated as possible targets for the pharmacological treatment of bladder hyperreflexia in patients with SCI.

Afferent Pathways↗
PubMed1995

Preparation and evaluation of sodium diclofenac controlled-release tablets. II. Dibasic calcium phosphate as a retardant in mixtures for direct compression.

The dissolution behaviour of a direct compression compact prepared with sodium diclofenac and dibasic calcium phosphate (DCP) in different weight ratios with or without Biosoluble polymer (acrylic-based resin) was investigated in distilled water and in a medium with changing pH. The results indicate that the amount of sodium diclofenac released from the compact was dependent on the amount of drug and DCP used in the compact, and was also controlled by the amount of Biosoluble polymer added. A chemical reaction forming diclofenac acid might occur on the surface of the sodium diclofenac compact during exposure to the acidic medium, which was confirmed by diffuse-reflectance spectroscopy. The tablet with a 1:2 weight ratio of sodium diclofenac to DCP exhibited a sustained-release behaviour, similar to commercial sustained-release products (Voltaren SR-100 and Grofenac Retard), but a lower release rate was found as compared to the commercial products. The dissolution behaviour of the study tablet and the commercial products was found to be dependent on the dissolution medium and the rotating speeds. Glass beads were added to the dissolution assembly to simulate the influence of food, and the enhanced friction between tablet and glass beads might result in a higher dissolution rate of the tablet and the commercial products.

Acrylates↗
PubMed1994

Acute pyloric perforation after prolonged crack smoking.

A 28-year-old homosexual man, previously healthy, presented with an acute abdomen on the fifth day of his crack binge. Abdominal free air was demonstrated by radiographic studies. Exploratory laparotomy discovered a clean, ulcer-free, pyloric perforation. This unusual case underscores the possibility of a life-threatening visceral perforation after cocaine use.

Abdomen, Acute↗
PubMed1994

5' proximal regions of Arabidopsis nitrate reductase genes direct nitrate-induced transcription in transgenic tobacco.

Nitrate reductase (NR) is the first enzyme in nitrate assimilation, a critical process for plant survival. The regulation of NR gene expression is complex, involving both internal and external factors. Of these, nitrate induction of NR gene expression has been studied most extensively and is well conserved among bacteria, fungi, and higher plants. We are interested in understanding the mechanism of nitrate induction of higher plant NR genes. Here we describe promoter analyses of the 5' flanking regions of the Arabidopsis NR genes, NR1 and NR2, with respect to nitrate induction of gene expression. To facilitate these analyses, a nitrate induction procedure using T1 transgenic tobacco plants was established. Approximately 1.5-kb 5' flanking regions of the two Arabidopsis NR genes (NR1 and NR2) were fused to a reporter gene and its expression in transgenic plants was analyzed. Deletion analyses of these regions show that 238- and 188-bp 5' flanking regions of the NR1 and NR2, respectively, contain sequences responsive to nitrate induction.

Arabidopsis↗
PubMed1994

Development of an azopolymer based colonic release capsule for delivering proteins/macromolecules.

The colon, high in microbial contents with degradation ability of azo bonds, seems to be suitable for site-specific delivery of drugs. The degradation of azoaromatic hydrogel depends on the degree of swelling. However, the degree of swelling of azopolymers and the ability of the azoaromatic polymers to protect peptide drugs against the action of digestive enzymes still remains to be established. An azopolymer was synthesized and membranes were cast to investigate the degree of swelling. An azopolymer-coated capsule suitable for delivering peptides/proteins to the colon was developed by in vitro evaluation using vitamin B12 as a model drug to screen various formulations. For in vitro dissolution the half-changed method was used to mimic the pH-time profile in the GI tract. It was shown that the release of vitamin B12 is dependent on the degree of swelling which increases as pH increases. An in vivo study was also performed with insulin in azopolymer-coated capsules in 6 normal beagle dogs. The results suggest that this azopolymer-coated capsule is capable of protecting peptide/macromolecules against digestive enzymes. However, to obtain a promising peroral insulin capsule, more formulation work is required to achieve better absorption availability.

Administration, Oral↗
PubMed1993

Vicryl mesh for repair of severely injured kidneys: an experimental study.

We evaluated the efficacy of wrapping the kidney with semi-elastic Vicryl mesh for control of hemorrhage and preservation of renal function following grade III kidney lacerations (shattered kidney) in dogs in which nephrectomy was indicated clinically. Wrapping of fragmented kidneys resulted in prompt, sustained hemostasis and reapposition of the renal parenchyma. At an average of 80 days after injury the renal lacerations were well healed. The Vicryl mesh had been fully reabsorbed and there was considerably less scar tissue at the site of parenchymal rupture and neither perirenal or intrarenal abscess nor hematoma was found, grossly or microscopically. Among 12 dogs with grade III kidney lacerations, the mean ratio of the effective renal plasma flow (ERPF) in the affected kidney to the ERPF in the uninjured contralateral kidney was 0.53 +/- 0.22. The mean ratio of creatinine clearance of the injured kidney to that of the uninjured contralateral kidney was 0.41 +/- 0.23. Changes in the serum renin levels were not statistically significant following injury. Our results seem to confirm that simple and rapid surgical treatment of severely shattered kidneys using semi-elastic Vicryl mesh is possible. The method may also be suitable for uncontrollable bleeding during nonextirpative kidney surgery.

Animals↗
PubMed1993

Effects of capsaicin on micturition and associated reflexes in rats.

The effect of capsaicin on micturition and associated reflexes was studied in urethan-anesthetized female rats. Capsaicin or vehicle solution were administered 4 days before the experiment in a dose of 125 mg/kg sc or during the experiment in a dose of 50-100 mg/kg sc. Activity of the urinary bladder was recorded by measuring intravesical pressure via a urethral catheter while slowly filling (0.052 ml/min) the bladder or when the bladder was distended beyond the micturition threshold and maintained at a constant volume. Pretreatment with capsaicin did not significantly change various parameters of urinary bladder function including micturition volume threshold or the amplitude, duration, and interval between reflex bladder contractions. However, capsaicin pretreatment significantly reduced (80% decrease) the arterial pressor responses accompanying reflex bladder contractions and reduced by approximately one-half the percentage of animals in which bladder activity was inhibited by stimulation of the uterine cervix. A large dose of capsaicin (50 mg/kg sc) elicited an acute block of bladder activity that persisted for 8-15 h. This effect is attributable to an action on myelinated afferent or efferent components of the micturition reflex pathway. It is concluded that capsaicin-sensitive afferents are not essential for the performance of micturition in the rat. However, these afferents are involved in cervicovesical reflex mechanisms that modulate bladder activity and in vascular reflexes triggered by isometric bladder contractions.

Animals↗
PubMed1993

Glutamate activation of neurons in CV-reactive areas of cat brain stem affects urinary bladder motility.

To investigate the interaction between cardiovascular (CV)-reactive areas in the brain stem and urinary bladder (UB) motility, 48 adult cats of either sex were anesthetized intraperitoneally with alpha-chloralose (40 mg/kg) and urethan (400 mg/kg). The changes of UB motility and systemic arterial blood pressure (SAP) were produced by microinjection of sodium glutamate (0.5 M, 100-200 nl) into the pressor, depressor, or vagobradycardiac areas of the brain stem. Stimulation of these CV-reactive areas increased or decreased UB motility. Areas that produced an increase in UB motility listed in decreasing order of effectiveness are locus ceruleus-parabrachial nucleus in the pons, dorsal medulla, dorsal motor nucleus of vagus, and ventrolateral medulla. Areas eliciting a decrease in UB motility listed in decreasing order are gigantocellular tegmental field, parvocellular reticular nucleus, and ambiguus nucleus. Stimulation of other pressor sites in medulla also increased UB motility. Activation of the paramedian reticular nucleus, which consistently produced depressor responses, and activation of raphe nuclei, which produced depressor or pressor responses, consistently decreased UB motility. The integrity of the vagus nerve was not essential for the UB response to brain stimulation. These findings indicate that neuronal mechanisms for controlling UB and CV functions coexist at many sites in the brain stem. At those sites that commonly produce changes in UB motility, the type of UB response (excitation or inhibition) was in the same direction as the change of SAP. However, at some sites responses were inverse. It is not known whether the responses of the UB and CV system are controlled by common or separate populations of neurons at these sites.

Animals↗
PubMed1992

Sucrose mimics the light induction of Arabidopsis nitrate reductase gene transcription.

Nitrate reductase, the first enzyme in nitrate assimilation, is located at the crossroad of two energy-consuming pathways: nitrate assimilation and carbon fixation. Light, which regulates the expression of many higher-plant carbon fixation genes, also regulates nitrate reductase gene expression. Located in the cytosol, nitrate reductase obtains its reductant not from photosynthesis but from carbohydrate catabolism. This relationship prompted us to investigate the indirect role that light might play, via photosynthesis, in the regulation of nitrate reductase gene expression. We show that sucrose can replace light in eliciting an increase of nitrate reductase mRNA accumulation in dark-adapted green Arabidopsis plants. We show further that sucrose alone is sufficient for the full expression of nitrate reductase genes in etiolated Arabidopsis plants. Finally, using a reporter gene, we show that a 2.7-kilobase region of 5' flanking sequence of the nitrate reductase gene is sufficient to confer the light or the sucrose response.

Gene Expression↗
PubMed1992

Bodysurfing accidents resulting in cervical spinal injuries.

During the summers of 1987 and 1988, 14 cervical spine injuries sustained during bodysurfing accidents at the beaches around Ocean City, Maryland presented to our Neurotrauma service. All the patients were men, predominantly in their middle years (mean age = 40), and otherwise healthy. Likely mechanisms of injury suggested by radiography and computed tomography-myelography included hyperflexion, hyperextension, and axial loading. Clinically, neurologic deficits were found in 10 patients (71%), of whom 2 were complete sensorimotor quadriplegics below the level of injury, and 8 were incomplete injuries. Of the eight incomplete injuries, two-thirds were central cord syndromes associated with narrow spinal canals and prominent osteophytes, and one-third had Brown-Sequard or anterior cord syndromes. After initial anatomic realignment by closed or open reduction, the injured cervical spines were stabilized either externally or internally. Two patients underwent laminectomies. These bodysurfing accidents, in marked contrast to other types of shallow water-diving accidents, predominantly involved older men and produced incomplete injuries. It is concluded that bodysurfing is peculiarly hazardous to healthy, middle-aged men, especially those endowed with a narrow spinal canal with or without osteophyte formation.

Adult↗
PubMed1992

Characterization of 3H-serotonin (5-HT) binding and effects on the phosphoinositides (PI) turnover in cultured C6 glioma and N2 neuroblastoma cells from rodents.

3H-5-HT (serotonin) binding and its displacement by various specific subtype ligands and effects on the phosphoinositides (PI) turnover were studied in cultured C6 glioma and N2 neuroblastoma cells from rodents. Saturation analysis of 3H-5-HT binding to C6 cells revealed that its Kd and Bmax were 3.0 nM and 18.0 pmole/mg protein respectively. DOI.HCl (5-HT2 agonist) and ketanserin (5-HT2 antagonist) had the highest affinities in the drug-displacement of 3H-5-HT binding to C6 cells studied. The IC50 values for DOI-HCl and ketanserin were 7.5 x 10(-7) and 3.5 x 10(-8) M respectively. 5-HT also induced 3H-PI breakdown and generated 3H-IP. The EC50 values for 5-HT for this event were in the dose range between 0.5 to 1.5 microM, and this 5-HT-induced response could be blocked by 5-HT2 antagonist ketanserin more effectively than the 5-HT1 antagonist or 5-HT3 antagonist studied. 3H-5-HT binding to N2 cells revealed that its Kd and Bmax were 4.0 nM and 80 pmole/mg protein respectively in the saturation analysis study. The drug-displacement of this binding revealed that MDL 72222 (5-HT3 antagonist) had a higher affinity than ketanserin. The IC50 values for MDL 72222 and ketanserin were 10 nM and 10 microM respectively, when 3 nM of 3H-5-HT was used. Our results indicate that the predominant receptor subtype of 5-HT in C6 and N2 cells are 5-HT2, and 5-HT3 respectively, and that the PI turnover is linked to 5-HT2, but not 5-HT3 receptor activation.

Animals↗
PubMed1992

Partial weight bearing after operations for hip fractures in elderly patients.

Factors affecting a patient's ability to carry out partial weight bearing after operation for hip fracture were studied in 100 patients. Seventy-six were able to do so. Significant factors included the muscle power of the good limbs and the mental state, whereas age, body-weight and type of operation were not significant. Logistical regression analysis showed that it was possible to predict a patient's partial weight bearing potential by simply testing the left hand grip and the 'Set' test score.

Aged↗
PubMed1991

Differential expression of the two Arabidopsis nitrate reductase genes.

The differential regulation of the two nitrate reductase (NR, EC 1.6.6.1) genes of Arabidopsis thaliana L. Heynh was examined. cDNAs corresponding to each of the NR genes (NR1 and NR2) were used to measure changes in the steady-state levels of NR mRNA in response to nitrate, light, circadian rhythm, and tissue specificity. Although nitrate-induction kinetics of the two genes are very similar, NR1 is expressed in the absence of nitrate at a higher basal level than NR2. Nitrate induction is transient both in the roots and leaves, however the kinetics are different: the induction and decline in the roots precede that in the leaves. Light induces the expression of each of the genes with significantly different kinetics: NR2 reached saturation more rapidly than did NR1. Both genes showed similar diurnal patterns of circadian rhythm, with NR2 mRNA accumulating earlier in the morning.

Journal Article↗
PubMed1991

Characterization of cis-acting sequences regulating root-specific gene expression in tobacco.

The expression of the tobacco root-specific gene TobRB7 was characterized. Gel blot hybridizations to RNA isolated from various tobacco tissues demonstrated that steady-state TobRB7 mRNA is not detected in expanded leaf, stem, or shoot apex tissue. To determine the spatial pattern of expression, in situ hybridization to root sections revealed that TobRB7 expression is localized to root meristem and immature central cylinder regions. The 5' flanking region of the gene was studied with respect to its ability to direct root-specific expression. Deletions of 5' flanking sequence were fused to the beta-glucuronidase (GUS) reporter gene and transformed into tobacco. Our data demonstrated that sequences 636 base pairs from the site of transcription initiation are sufficient to direct the root-specific GUS expression in transgenic tobacco, whereas sequences 299 base pairs from the site of transcription initiation fail to direct root-specific expression. A negative regulatory element was apparent between 813 base pairs and 636 base pairs 5' of the transcription initiation site. Histochemical localization of GUS activity in transgenic plants was consistent with in situ hybridization results: GUS activity was localized to the root meristem and central cylinder regions. GUS activity appeared 2 days post-germination in the primary root meristem. In lateral roots, GUS activity was detected from the time of initiation.

Amino Acid Sequence↗
PubMed1991

[Clinical and experimental research on chronic bronchitis treated with ke chuan ping decoction].

This paper presents the results of clinical observation and experimental research of ke chuan ping (KCP) in treating 31 cases of chronic bronchitis compared with that of traditional prescription qing jin hua tan decoction (QJHT) in other 31 patients with the same conditions randomized as control. The total effective rate of KCP group was 93.55% including 67.74% of basically cured and markedly effective cases. The total effective rate of QJHT group was 74.19% including 41.94% basically cured and markedly effective cases. There were significant differences between them (P less than 0.05). According to laboratory observation KCP had the ability to dilute sputum viscosity, promote pulmonary ventilation function, decrease WBC and raise PO2. Animal experimental research suggested that KCP had the effects on reducing sputum, relieving cough, modifying stridor and inhibiting bacteria. It was proved that KCP is a highly effective recipe for patients with chronic bronchitis. It was also shown that clearing away heat and dispersing phlegm therapy is an important measure for chronic bronchitis with Biao Zheng.

Adult↗
PubMed1990

Mechanisms underlying the recovery of urinary bladder function following spinal cord injury.

Micturition in cats and rats with an intact neuraxis is dependent upon a spinobulbospinal reflex activated by A delta bladder afferents. This report describes changes in micturition reflexes 2 h to 14 weeks following spinal cord transection at the lower thoracic level. In acute spinal cats micturition reflexes were blocked, however, several weeks after transection, a long latency (180-200 ms) spinal reflex could be activated by C-fiber bladder afferents. This reflex was blocked by capsaicin in doses (20-30 mg/kg, s.c.) that did not affect micturition reflexes in intact cats. Micturition reflexes were unmasked in acute spinal and facilitated in chronic spinal cats by naloxone, an opioid antagonist. Spinal neurons and axons containing opioid peptides were more prominent below the level of transection in chronic spinal cats. VIP, a putative neurotransmitter in C-fiber bladder afferents, inhibited micturition reflexes when injected intrathecally (2-10 micrograms) in intact cats but facilitated micturition reflexes in spinal cats (doses 0.1-1 micrograms, i.t.). VIP-containing C-fiber afferent projections to lamina I of the sacral spinal cord expanded in spinal cats. Thus VIP afferents may have an important role in the recovery of bladder reflexes after spinal injury. Paraplegic animals also exhibit bladder-sphincter dyssynergia, which causes functional outlet obstruction. Studies in rats have revealed that outlet obstruction induced by partial urethral ligation facilitates spinal micturition reflex pathways and causes an expansion of HRP-labelled bladder afferent projections in the spinal cord. These findings raise the possibility that the alterations in central reflex connections in paraplegic animals may be induced in part by changes in peripheral afferent input secondary to outlet obstruction.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗