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Biomedical subjects

N Lee

Publications and source records attributed to N Lee.

At least 253 records · Page 14Linked to original sources
PubMed1988

A rapid multicolor Western blot.

A multicolor Western blotting technique was developed, by which different kinds or different subtypes of interferon were identified with different colors on a single Western blot. This was achieved by sequentially applying different sets of probing antibodies, enzyme-conjugated developing antibodies and enzyme substrates to detect each of the two or more types of interferon on the Western blot. An improved and much faster method of obtaining the same result by the simultaneous application of more than one kind of probing antibodies, the simultaneous application of a mixture of different enzyme-conjugated developing antibodies followed by successive application of different substrates was also described. In addition, a combination of the sequential and simultaneous techniques was used to produce a triple color Western blot.

Collodion↗
PubMed1988

Chronic haloperidol administration increases the density of D2 dopamine receptors in the medial prefrontal cortex of the rat.

Rats received haloperidol (1.3-1.5 mg/kg/day) via their drinking water for 21 weeks. At the end of this period the density of D2 dopamine receptors and their affinity for [3H]-spiperone were measured in the striatum and medial prefrontal cortex. The chronic haloperidol treatment increased the density of D2 receptors in the striatum by 70% and in the medial prefrontal cortex by 50%. The chronic haloperidol did not significantly alter the apparent affinity of D2 receptors for [3H]-spiperone in either structure. These results indicate that the density of D2 receptors in the medial prefrontal cortex is influenced by chronic exposure to haloperidol in a manner that is very similar to the well-documented increase that occurs in the striatum.

Animals↗
PubMed1988

Outpatient pediatric neurosurgery.

In a 16-month period, 31 children underwent outpatient operations for a variety of neurosurgical problems. None of the patients experienced any anesthetic complications. One patient was admitted for management of a surgical complication and was discharged uneventfully 4 days later. A saving of at least 49.5% in hospital charges was produced when surgery was performed in the outpatient surgical facility, and a 19.8% reduction in costs was achieved when the main hospital operating suite was used on an outpatient basis. Neurosurgical procedures can be safely and inexpensively performed on an outpatient basis, even in children.

Ambulatory Care↗
PubMed1988

Intra-cerebral cysteamine infusions attenuate the motor response to dopaminergic agonists.

Previous studies have suggested that somatostatin neurons in the basal ganglia may be involved in motor activity. In the present experiments, the effects of cysteamine, a drug which reduces somatostatin levels, on the basal and dopamine-mediated motor activities were examined in the rat. Neither intra-striatal nor intra-accumbens infusions of cysteamine had any effect on motor activity prior to the administration of dopamine agonists. However, intra-striatal cysteamine infusions reduced the duration of the stereotypic behavior induced by systemic apomorphine. In addition, intra-accumbens infusions of cysteamine produced a slight reduction in the locomotor response induced by amphetamine. The direct intra-cerebral infusion of cysteamine produced a significant depletion in the levels of somatostatin at the site of injections as measured by radioimmunoassay. These results indicate that somatostatin neurons in the basal ganglia may modulate the motor responses following dopaminergic activation, and further support the presence of a dopamine-somatostatin interaction in this region.

Animals↗
PubMed1988

Three binding sites for AraC protein are required for autoregulation of araC in Escherichia coli.

Three binding sites for AraC protein were shown to be required for the autoregulation of araC: araI1, araO1, and araO2. Selective inactivation of AraC-binding sites on the DNA demonstrated that araO1 and araO2 are required in vivo to produce repression of araC in the presence of arabinose, whereas araI1 and araO2 are required in its absence. We found that the low-affinity site araO2 is essential for araC autoregulation; araO1 and araI1 provide high-affinity AraC-binding sites, which allow cooperative binding at araO2. Profound effects on the araBAD promoter and the araC promoter are produced by ligand-induced changes in AraC occupancy of functional sites on the DNA. We suggest that AraC exerts its multiplicity of controls through two alternative states of cooperative interactions with DNA and we illustrate this with a model. This model presents our interpretations of activation and repression of the araBAD operon and the autoregulation of the araC gene.

AraC Transcription Factor↗
PubMed1987

Intraventricular administration of l-kynurenine and kynuramine facilitates lordosis in the female rat.

Intraventricular administration of the tryptophan metabolites l-kynurenine (2-32 micrograms) and kynuramine (0.064-8 micrograms) facilitated lordosis behavior in estrogen-primed ovariectomized rats. The facilitatory effects of these drugs were not attenuated by pretreatment with the progesterone antagonist RU 38486, indicating that the effects were not mediated by release of adrenal progesterone. It is suggested that l-kynurenine and kynuramine may serve a physiological role in the modulation of female sexual behavior.

Animals↗
PubMed1987

The human apoB-100 gene: apoB-100 is encoded by a single copy gene in the human genome.

Northern blot analysis of human liver and intestine mRNA revealed two separate apoB mRNA of 14.1 and 7.5 kb in the intestine, and a single 14.1 kb apoB mRNA in the liver. cDNA probes which encode for the 5', middle, and 3' regions of the human apoB-100 mRNA have been utilized to evaluate the number of apoB genes present in the human genome by Southern blot hybridization analysis. Comparison of restriction enzyme digestions of high molecular weight leukocyte DNA and a known apoB genomic clone with cDNA probes for the 5', middle and 3' regions of the apoB-100 mRNA were consistent with only a single apoB gene per human haploid genome. Further analysis with synthetic oligonucleotides definitively established that there is a single apoB-100 gene. The two mRNA species observed in the intestine must be derived from a single nuclear apoB RNA transcript.

Apolipoprotein B-100↗
PubMed1987

Modification of mRNA secondary structure and alteration of the expression of human interferon alpha 1 in Escherichia coli.

A plasmid (pNL015) was constructed to contain a human interferon alpha 1 (IFN-alpha 1) gene under the transcriptional control of the Escherichia coli lipoprotein promoter. The E. coli cells harboring this plasmid produce 2.8 x 10(4) units/ml of IFN. Secondary structure analysis of the transcripts produced by pNL015 showed that the coding region could base pair with the Shine-Dalgarno (SD) region with a delta G = -3.9kcal/mol. A new plasmid pNL008 was constructed by modifying pNL015 with an 11-bp deletion and a 2-bp insertion in the coding region, so that the SD region is not involved in the secondary structure. E. coli cells harboring pNL008 produce ten times more IFN activity than cells harboring pNL015. A series of experiments were carried out to show that the specific activities of IFN, differential rates of IFN transcription, protein degradation or mRNA degradation could not account for the difference observed in expression. A rigorous test on this model of translational inhibition was conducted by the construction of pNL017 with a single bp substitution which did not change the amino acid sequence of the IFN (synonymous codon substitution) but which increased the calculated energy of interaction with the SD sequence to delta G = -10.8 kcal/mol. The E. coli cells harboring pNL017 produced no detectable IFN activity.

Base Sequence↗
PubMed1987

The ratio of mid-arm circumference to occipital frontal circumference in Chinese babies: a marker of late gestation growth retardation.

The ratio of mid-arm circumference to occipital frontal circumference (MAC/OFC), an index of late gestation growth retardation, was determined in 175 healthy newborn term Chinese babies. The ratio of 0.31 (S.D., 0.02) was significantly higher than in recent data published for Asian, White and Black neonates: whether this is due to differences in measuring techniques or better intra-uterine nutrition remains to be seen. As an initial test of its potential usefulness this ratio was determined in 12 term Chinese babies who showed clinical signs of undernutrition. All but one had a ratio 2S.D. or more below the mean. The MAC/OFC ratio, with its ease of measurement, simplicity and cheapness, is a useful addition to existing methods for assessing late gestation nutritional status.

Arm↗
PubMed1987

Arabinose-induced binding of AraC protein to araI2 activates the araBAD operon promoter.

The state of Escherichia coli araI DNA occupancy by AraC protein has been found to change from a two-turn to a four-turn occupancy upon the addition of the inducer arabinose. The araI site is separable into two contiguous regions, araI1 and araI2. araI1 binds both ligand-bound and ligand-free AraC protein, whereas araI2 binds AraC protein in the presence of arabinose only. A mutation in araI and a known mutation in araC led to the loss of araI2 binding, while binding to araI1 was unaffected. Both mutants failed to activate the promoter of the araBAD operon. We propose that araI2 occupancy by AraC protein leads to RNA polymerase recognition of the araBAD promoter and that araI1 acts as a switch mechanism allowing both the repressor and the activator forms of AraC protein to regulate the araBAD promoter.

Arabinose↗
PubMed1987

Repression and catabolite gene activation in the araBAD operon.

Catabolite gene activation of the araBAD operon was examined by using catabolite gene activator protein (CAP) site deletion mutants. A high-affinity CAP-binding site between the divergently orientated araBAD and araC operons has been previously identified by DNase I footprinting techniques. Subsequent experiments disagreed as to whether this site is directly involved in stimulating araBAD expression. In this paper, we present data showing that deletions generated by in vitro mutagenesis of the CAP site led to a five- to sixfold reduction in single-copy araBAD promoter activity in vivo. We concluded that catabolite gene activation of araBAD involves this CAP site. The hypothesis that CAP stimulates the araBAD promoter primarily by relieving repression was then tested. The upstream operator araO2 was required for repression, but we observed that the magnitude of CAP stimulation was unaffected by the presence or absence of araO2. We concluded that CAP plays no role in relieving repression. Other experiments showed that when CAP binds it induces a bend in the ara DNA; similar bending has been reported upon CAP binding to lac DNA. This conformational change in the DNA may be essential to the mechanism of CAP activation.

Base Sequence↗
PubMed1987

A prospective study on the intrauterine growth of Hong Kong Chinese babies.

A prospective study on the birth weight, crown-heel length and head circumference of 8,445 singleton Chinese newborn infants born between 27 and 42 weeks of gestation was conducted in three major regional maternity units in Hong Kong over a 3 1/2-year period. The data were used to construct centile charts for the intrauterine growth of each physical measurement. By careful gestational assessment of the infants, primary exclusion of pregnancies complicated by abnormal fetal or maternal conditions that might have affected fetal growth together with infants of doubtful maturity, these curves depict more accurately the prenatal growth of Chinese infants than those previously published in studies on similar populations of infants. Chinese infants, as shown by the findings of the present study, are similar in their mean weight to Japanese infants and American infants in Denver but are lighter than British and Australian infants, as well as American infants born at sea level.

Asian People↗