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Biomedical subjects

N Hu

Publications and source records attributed to N Hu.

104 records · Page 6Linked to original sources
PubMed1985

Effect of environmental hypothermia on vitelline artery blood pressure and vascular resistance in the stage 18, 21, and 24 chick embryo.

We studied the effect of environmental hypothermia on arterial blood pressure, dorsal aortic blood flow, and vascular resistance in stage 18, 21, and 24 chick embryos. The arterial pressure was measured with a servonull micropressure system. Mean dorsal aortic blood flow was calculated from pulsed-Doppler measurement of mean dorsal aortic blood velocity and dorsal aortic diameter. Vascular resistance was calculated by dividing mean vitelline arterial blood pressure by dorsal aortic blood flow. Sequential data were obtained at temperatures of 34.7, 31.1, and 34.1 degrees C. At stage 21, the vitelline arterial blood pressure decreased from 0.82 +/- 0.03 (means +/- SEM) to 0.72 +/- 0.03 mm Hg on cooling and increased from 0.66 +/- 0.05 to 0.87 +/- 0.06 mm Hg on rewarming (p less than 0.05). At stage 21, mean dorsal aortic blood flow decreased from 0.49 +/- 0.02 to 0.33 +/- 0.02 mm3/s with cooling and increased from 0.34 +/- 0.02 to 0.47 +/- 0.02 mm3/s with rewarming. The vascular resistance in stage 21 embryos increased after cooling from 1.68 +/- 0.19 to 2.23 +/- 0.39 mm Hg/mm3/s (means +/- 95% confidence interval). The changes were similar in stage 18 and 24 embryos. We conclude that the reduction of vitelline artery blood pressure resulted from a decrease in cardiac output. In addition, we noted that the vitelline arterial vascular bed can constrict in response to hypothermia prior to autonomic innervation. These changes in hemodynamics may be a teratogenic mechanism for hypothermia-induced cardiac defects in the chick embryo.

Animals↗
PubMed1984

Effect of conotruncal constriction on aortic-mitral valve continuity in the stage 18, 21 and 24 chick embryo.

The effect of conotruncal constriction on the development of aortic-mitral valve continuity in stage 18, 21 and 24 chick embryos was studied. A 10-0 nylon suture was tied around the conotruncus, constricting the outflow tract of the heart. The loop was removed after 4 or 24 hours or left permanently in place in 3 subgroups of the 236 experimental embryos. The embryo hearts were harvested at stages after completion of cardiac morphogenesis, fixed in end-diastole and microdissected. The distance between the mitral and aortic anuli was measured from the base of the heart with a calibrated filar micrometer eyepiece. This measurement was compared with the mitral-aortic separation in 72 normal and 132 control embryos. The mitral-aortic separation was similar among normal, control and 4- and 24-hour experimental embryo hearts. However, the mitral-aortic separation increased from 0.34 +/- 0.02 mm in normal hearts to 0.82 +/- 0.25 mm in stage 18, 1.11 +/- 0.36 mm in stage 21 and 0.75 +/- 0.33 mm in stage 24 permanent loop experimental hearts (p less than 0.01). In embryo hearts with an increased mitral-aortic separation, both great vessels arose from the right ventricle, the semilunar valves were at the same level and the ventricular septal defect was present beneath the aortic anulus. We conclude that conotruncal constriction modifies the relation of the aortic and the mitral valve. We speculate that conotruncal constriction alters the migration of mesenchymal tissue into the heart.

Animals↗
PubMed1984

Effect of caffeine on cardiovascular function in the stage 24 chick embryo.

Caffeine is consumed by an estimated 95% of pregnant women. Yet, it is not known if caffeine alters embryonic cardiovascular function. We measured the effect of caffeine on mean and phasic dorsal aortic blood flow and mean vitelline artery pressure with a 20-MHz pulse Doppler velocity meter and a servo-null pressure system, respectively. We calculated vascular resistance, stroke volume index, and heart rate. We injected 5-microliters aliquots of anhydrous caffeine dissolved in chick Ringer's lactate into a vitelline vein in doses from 1.2 X 10(-5) mg (0.15 mg/kg) to 1.2 X 10(-2) mg (150 mg/kg). Control embryos received 5 microliters chick Ringer's lactate. The hemodynamic measurements were continuously recorded from 1 min prior through 5 min after injection. 9 stage 24 chick embryos were studied at each dose. The data were analyzed by one-way analysis of variance and Tukey's HSD test. Caffeine had no effect on heart rate, but a direct dose-related effect on mean dorsal aortic blood flow, stroke volume index, mean pressure, and vascular resistance. The effect of caffeine on stroke volume index at 5 min was a linear log-dose relationship [y = 0.155 + 0.02 1n (dose), p less than 0.001]. In the chick, caffeine acutely affects cardiovascular function by increasing myocardial contractility and dilating resistance vessels. We speculate this action is mediated through direct cellular effects: increase in free Ca++ and cyclic adenosine monophosphate.

Animals↗
PubMed1983

Effect of environmental hypothermia on dorsal aortic blood flow in the chick embryo, stages 18 to 24.

Dorsal aortic blood flow was measured with a pulsed-Doppler meter in Hamburger-Hamilton stage 18, 21, and 24 chick embryos, and stroke volume index was calculated by dividing mean blood flow per minute by heart rate. These parameters were measured at baseline temperature 34.7 degrees C after cooling to 31.1 degrees C and subsequent rewarming to 34.2 degrees C. In stage 21 embryos, after environmental cooling, heart rate decreased from 170 bpm to 118 bpm (P less than 0.01), mean dorsal aortic blood flow decreased from 0.38 mm3/sec to 0.24 mm3/sec (P less than 0.01) but stroke volume index did not change [baseline, 0.13 mm3/beat; after cooling, 0.12 mm3/beat; after rewarming, 0.15 mm3/beat (P = N.S.)]. Similar results were observed in stage 18 and 24 embryos. The bradycardic response to environmental hypothermia was independent of functional autonomic innervation and probably mediated by a direct suppression of cell action potential dv/dt. Myocardial cell function was not adversely affected by an acute change in environmental temperature as the index of stroke volume was not altered, and all parameters returned rapidly to baseline with rewarming.

Action Potentials↗
PubMed1982

The making of strand-specific M13 probes.

A novel approach has been developed for the preparation of highly radioactive, strand-specific M13 probes. A universal primer, complementary to the region 5' to the multiple cloning sites of M13mp7, was used to initiate the DNA synthesis of the complementary strand of the M13 sequence downstream from the inserted sequence. The synthesis of the (-) strand, which was labeled with a radioactively labeled precursor, did not proceed to completion so that the inserted sequence was kept single-stranded. Thus, a partially double-stranded probe that had the specificity of this inserted sequence was obtained. As an example for the application of single-stranded specific hybridization probes, an M13mp7 subclone of a zein cDNA clone of maize (A30) was labeled and used in a dot hybridization test to select from the hundreds of M13mp7 subclones of the zein genomic clone, Z4, the sequences complementary to the probe. The specificity of the probe was confirmed by dideoxy chain terminator sequencing experiments.

Base Sequence↗
PubMed1982

Developmental hemodynamic changes in the chick embryo from stage 18 to 27.

We report the hemodynamic parameters of stage 18, 21, 24, and 27 chick embryos (from 3 to 5 days of incubation). Dorsal aortic blood velocity and mean vitelline artery blood pressure are measured with a 20 MHz pulsed-Doppler meter and servo-null pressure system respectively. We also measure heart rate, dorsal aortic diameter and embryo weight of each developmental stage. From these data, we calculate mean dorsal aortic blood flow, mean dorsal aortic blood flow per cardiac cycle, mean dorsal aortic blood flow per milligram embryo weight, vascular resistance and cardiac work. Blood flow increases geometrically with each embryo stage but remains constant when normalized for embryo weight. Mean arterial pressure increases linearly and vascular resistance decreases geometrically. Cardiac work increases in proportion to embryo weight. These results define the parameters of normal hemodynamic function during early embryonic development.

Animals↗
PubMed1977

NMR in cancer: XVII. dewar for a 53-inch superconducting NMR magnet.

A giant nitrogen-jacketed liquid-helium metal dewar built in this laboratory is described for housing 53-inch superconducting magnet used in the human FONAR experiments. This dewar is 10 feet tall, 6 feet wide, 18 inches deep, and weighs 1 1/2 tons. It consists of the main magnet hoop connected through a demountable gooseneck to a liquid helium reservoir tank.

Electromagnetic Phenomena↗
PubMedDate not supplied

Effects of age and dietary restriction on liver glutathione transferase activities in Lobund-Wistar rats.

Glutathione-S-transferases (GST) are a group of enzymes which detoxify electrophilic xenobiotics (including drugs, carcinogens and their metabolites), and thus may be involved in the age-related pathologic process. Effects of a 30% dietary restriction on liver GST activities toward seven substrates were studied in male Lobund-Wistar (L-W) rats at 6, 12, 18, 24 and 30 months of age. The enzyme activities in the ad libitum (AL) group toward 1-chloro-2,4-dinitrobenzene (CDNB), bromosulfophthalein (BSP), 4-nitropyridine-N-oxide (NPNO), p-nitrobenzyl chloride (NBC), trans-4-phenyl-3-buten-2-one (PBO) and styrene oxide (STOX) did not change with age, while those toward 1,2-dicholoro-4-nitrobenzene (DCNB) decreased after middle age. The enzyme activities in the dietary restricted (DR) group toward CDNB and STOX did not change with age, while those toward DCNB, BSP, NPNO, NBC and PBO decreased after middle age. The DR group had significantly higher GST activities than the AL group, especially at 18 months, when BSP, NPNO, NBC and PBO were used as the substrates. Dietary restriction did not affect GST activities toward all seven substrates at old age. These results are substrate-specific, indicating that isozyme-specific changes in GST activities occur with dietary restriction and aging. The results suggest that dietary restriction enhances liver detoxification capability associated with GSH conjugation in middle age, which may contribute to the delaying of the age-related pathologic process until a later point in life in this animal model.

Journal Article↗
PubMedDate not supplied

Expression of cyclooxygenase-2 in human adenocarcinomas of the gastric cardia and corpus.

Several studies indicate that the use of non-steroidal anti-inflammatory drugs (NSAIDs) may reduce the risk of gastric corpus and possibly gastric cardia cancers. The best known action of NSAIDs is to block the enzyme cyclooxygenase, the rate limiting enzyme in the conversion of arachidonic acid to prostaglandins. We investigated the expression of cyclooxygenase-2 (Cox-2) in adenocarcinomas of the gastric cardia (N=19) and corpus (N=15) and in adjacent normal epithelium from a high risk Chinese population. Immunohistochemical detection of Cox-2 revealed positive staining in 36% of the gastric cardia cancer cases and 60% of the gastric corpus cancer cases, whereas histologically normal tissue from the same patients were negative. Smooth muscle, stroma and inflammatory cells were also positive. Our results suggest that Cox-2 is overexpressed in a large proportion of adenocarcinomas of the gastric corpus and in a smaller number of gastric cardia cancer cases.

Adenocarcinoma↗
PubMedDate not supplied

Expression of cyclooxygenase-2 in human squamous cell carcinoma of the esophagus; an immunohistochemical survey.

Several studies indicate that the use of non-steroidal anti-inflammatory drugs (NSAIDs) may reduce the risk of esophageal cancer. The best known function of NSAIDs action is to block the enzyme cyclooxygenase, the rate limiting enzyme in the conversion of arachidonic acid to prostaglandins. In this study we investigated the expression of cyclooxygenase-2 (Cox-2) in squamous cell cancers of the esophagus and in normal esophageal squamous epithelium. Immunohistochemical detection of Cox-2 revealed strong positive staining in the well-differentiated regions of esophageal tumors, whereas histologically normal squamous epithelium stained only weakly positive. Smooth muscle cells, some stromal and inflammatory cells were also positive. Poorly differentiated areas of the esophageal tumors were negative. Our results suggest that Cox-2 is over-expressed in well-differentiated regions of squamous cell cancers of the esophagus.

Adolescent↗