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Biomedical subjects

L Hu

Publications and source records attributed to L Hu.

At least 163 records · Page 9Linked to original sources
PubMed1994

Activation of keratin 19 gene expression by a 3' enhancer containing an AP1 site.

We previously reported that the human keratin 19 (K19) gene was expressed in nonkeratinizing oral epithelial subtypes, and that the steady state K19 mRNA levels in different normal epithelial subtypes correlated with the levels of the retinoic acid receptor (RAR) beta-mRNA (Hu, L., Crowe, D. L., Rheinwald, J. G., Chambon, P., and Gudas, L. J. (1991) Cancer Res. 51, 3972-3981). To elucidate the mechanisms by which the K19 gene is differentially expressed in various epithelial subtypes, we isolated phage containing human K19 genomic DNA from a human placental library. Through transient transfection assays with various K19/CAT constructs that contain different portions of K19 genomic DNA, an enhancer sequence has been identified in the K19 3'-flanking region. In normal human epithelial cell strains, the activity of this enhancer correlates with K19 mRNA abundance. This enhancer activates both the K19 and TK basal promoters in HeLa cells. A high level of K19/CAT fusion mRNA was detected when this K19 3' enhancer sequence was present at the 3' end of the fusion gene whereas no K19/CAT fusion transcript was detected if this 3' K19 enhancer sequence was absent, suggesting that the 3' K19 enhancer is crucial for the positive regulation of K19 expression. Deletion analysis has permitted the localization of the enhancer to a 19-base pair sequence which contains an AP1 binding site (AGTCATCT). Point mutations within this AP1 site completely abolished K19 enhancer activity in HeLa cells. Co-transfections of a c-jun expression vector with K19/CAT reporter constructs demonstrated that c-jun was able to activate the K19 promoter via the 3' K19 enhancer. Collectively, these data indicate that a cis-acting AP1 element and its associated trans-acting effector proteins regulate expression of lineage-specific genes in epithelial cells.

Base Sequence↗
PubMed1994

Hippocampal synaptic pathology in patients with temporal lobe epilepsy.

Immunostaining of synaptic terminals was studied in the hippocampus of 26 patients who had surgical resections for intractable temporal lobe epilepsy. Two monoclonal antibodies (EP10 and SP12) reactive with distinct synaptic antigens were used on paraffin-embedded tissues. The results indicated qualitative reductions on synaptic terminals in CA4 and other regions where cell loss is reported. The inner molecular layer of the dentate gyrus was observed to have increased synaptic immunostaining. Synaptic terminal loss in CA4 and redistribution in the molecular layer were most frequent in cases with hippocampal sclerosis. However, both forms of synaptic pathology were also noted in most cases where the pathological findings were classified as indefinite, and in some cases associated with mass lesions of the temporal lobe. These results support the importance of neuronal loss and synaptic reorganization as possible mechanisms of illness in epilepsy. They also indicate that synaptic immunostaining may be a useful adjunct to routine neuropathological diagnostic techniques.

Adolescent↗
PubMed1994

Neuropeptide Y acylation chemistry in aqueous solution: significance to synthesis of a peptide-based photoaffinity label.

Treatment of neuropeptide Y (NPY, 1) for 20 hr with a 20 equivalent excess of N-propionyl succinimide (2) in 10 mM phosphate buffer, pH 6.0, yields NPY and N alpha-propionyl-NPY (3) as major products, and at pH 7.5 the major product is N alpha, N epsilon-dipropionyl-NPY. However, acylation of NPY with one equivalent of N-(5-azido-2-nitrobenzolyloxy)-succinimide (5) is more rapid, yielding N alpha-(5-azido-2-nitrobenzoyl)-NPY (6) in 70% conversion yield after only 5 min. Thus, in spite of its increased reactivity, the N-hydroxysuccinimide active ester shows enhanced alpha- vs. epsilon-NH2 selectivity relative to 2. The activities of 3, 4, and 6 as reversible, competitive ligands at rat brain NPY binding sites and of 6 as an irreversible photoaffinity label are reported.

Acylation↗
PubMed1994

Distribution of lactotroph subpopulations in different regions of the rat pituitary.

In this study, we examined the distribution of lactotrophs in different regions of pituitaries of ovariectomized (OVX) rats either untreated or treated with estradiol, progesterone or a combination of estradiol and progesterone. Anterior pituitaries were cut into inner and outer zones. Each of these regions was enzymatically dispersed and the resulting cells subjected to density sedimentation through a discontinuous Percoll gradient. The light and heavy cell subpopulations obtained were compared with cells not subjected to Percoll (unseparated cells). Cell numbers were determined and prolactin positive cells were assessed by immunocytochemistry. In OVX rats, the percentage of lactotrophs in the unseparated cell fraction of the outer zone was significantly (P < 0.05) lower than that in the inner zone. Estradiol increased the percentage of PRL cells in all cell populations, but the effect on inner zone light cells was significantly less than on any other type of cells. Progesterone given alone did not affect the percentage of lactotrophs in pituitary compared to untreated OVX rats nor did it alter the effects of estradiol. When the number of lactotrophs was calculated, the unseparated cells of inner and outer zone were equivalent except in the untreated OVX group where there was a significantly greater number of lactotrophs in the outer zone. In untreated OVX rats there was an equal distribution of lactotrophs between light and heavy cells in both inner and outer zones. Estradiol significantly increased the number of PRL cells in both zones and the effect was greater in the heavy cell fractions especially in the outer zone. In contrast, progesterone decreased the number of PRL positive cells in both zones and across cell types, but this effect was most pronounced in the outer zone. Progesterone also decreased the total pituitary cell number and this effect was greater than could be accounted for by the decrease in lactotroph numbers. We conclude that, except in untreated OVX rats, the numbers of lactotrophs in inner and outer zones are similar. The results also indicate that estradiol and progesterone can significantly alter the proportion and/or numbers of PRL positive cells within pituitary zones and may also affect cells that are not identified as PRL positive.

Animals↗
PubMed1994

Identification of the epitopes on human type VII collagen for monoclonal antibodies LH 7.2 and clone I, 185.

Type VII collagen is the major component of anchoring fibrils, structures in human skin that mediate the adherence of the epidermis to the underlying dermis. Dystrophic forms of epidermolysis bullosa, a group of inherited mechanobullous disorders of the skin, are linked to the type VII collagen gene. Several mutations in the recessive form of this inherited disorder have been delineated. In this study, we mapped the epitopes of two commercially available monoclonal antibodies (clone I, 185 and LH 7.2) within the amino-terminal, non-collagenous domain of type VII (anchoring fibril) collagen. The precise localizations of the epitopes for these two monoclonal antibodies which are widely used to diagnose dystrophic epidermolysis bullosa, will be useful for the confirmation of gene mutations at the protein level.

Antibodies, Monoclonal↗
PubMed1994

Expression of Ki67 antigen, epidermal growth factor receptor and Epstein-Barr virus-encoded latent membrane protein (LMP1) in nasopharyngeal carcinoma.

The expression of Ki67 antigen, epidermal growth factor receptor (EGFR) and the Epstein-Barr virus (EBV)-encoded latent membrane protein (LMP1) in nasopharyngeal carcinoma (NPC) was immunohistochemically determined. In cases with sufficient material western blot analysis was applied to analyse the LMP1 expression. Biopsies from 20 Chinese and 3 Swedish patients with NPC were included in the study. Our results demonstrated a nuclear Ki67 staining, a membrane EGFR staining, and a dot-like cytoplasmic and/or membrane LMP1 staining pattern in tumour cells of NPC. The proportion of Ki67-positive cells correlated with tumour stage. A strong expression of EGFR was frequently seen in patients with tumour stages III and IV and was paralleled by a higher proportion of Ki67-positive cells. The majority of the LMP1-positive cases strongly expressed EGFR and had a higher proportion of Ki67-positive cells, indicating a possible effect of EBV LMP1 on the proliferation of tumour cells in NPC. The increased expression of EGFR and Ki67 in NPC at late tumour stage indicates their possible use in malignancy grading of NPC.

Biomarkers, Tumor↗
PubMed1994

Type VII collagen specifically binds fibronectin via a unique subdomain within the collagenous triple helix.

Type VII collagen is the major component of anchoring fibrils, structures within basement membranes beneath stratified squamous epithelium thought to mediate the adherence of the epidermis to the dermis of human skin. Type VII collagen has affinity for fibronectin. The interaction between type VII collagen and fibronectin is mediated through the collagen-binding domain on the amino terminus of fibronectin. Heretofore, the domain on the type VII collagen molecule that binds to fibronectin was not known. In this study, we mapped the binding site of fibronectin to a specific subdomain of the triple helical collagenous region of type VII collagen, immediately adjacent to the small carboxyl terminal non-collagenous domain. This fibronectin-binding site within the type VII collagen molecule lies between nucleotide residues 615 and 1161.

Amino Acid Sequence↗
PubMed1994

Long-term cardiovascular role of nitric oxide in conscious rats.

The goal of this study was to determine the arterial pressure and renal excretory responses to a continuous intravenous infusion of 7.4 nmol/kg per minute of the nitric oxide synthesis inhibitor NG-nitro-L-arginine methyl ester (L-NAME) in conscious rats. Studies were conducted in six groups of Sprague-Dawley rats with indwelling arterial and venous catheters over periods lasting 12 to 26 days. In the first group of rats, L-NAME infusion for 9 days caused a sustained increase in arterial pressure, and on the ninth day arterial pressure was increased 29 mm Hg. Infusion of L-NAME at the higher dose of 37 nmol/kg per minute for 9 days caused no greater increase in arterial pressure than the lower dose. Sodium and volume balances and phenylephrine pressor sensitivity were unchanged during L-NAME administration at 7.4 nmol/kg per minute; plasma renin activity increased 2.5-fold, but the vasodepressor and vasodilator responses to acetylcholine and bradykinin were unchanged. Arterial pressure remained significantly increased 7 days after L-NAME was stopped, but in another group of rats, intravenous L-arginine infusion caused arterial pressure to return to control within 1 day. This same dose of L-arginine was administered for 7 days intravenously, and neither arterial pressure nor sodium balance changed. In other groups of rats, L-arginine was administered in conjunction with L-NAME; this prevented any change in arterial pressure, whereas D-arginine did not. In conclusion, the data suggest that continuous intravenous infusion of L-NAME causes sustained increases in arterial pressure in conscious rats without any sodium or water retention. The hypertension is accompanied by increases in plasma renin activity and can be prevented with intravenous L-arginine administration.

Animals↗
PubMed1994

Nitric oxide regulates renal hemodynamics and urinary sodium excretion in dogs.

The goal of this study was to determine whether nitric oxide has a long-term role in the control of renal hemodynamics and the relation between arterial pressure and urinary sodium excretion. Studies were conducted over a 25-day period in seven conscious dogs equipped with indwelling vascular catheters and an electromagnetic flow probe on the iliac artery. Nitric oxide synthesis was inhibited by continuous intravenous infusion of NG-nitro-L-arginine methyl ester at 37.1 nmol/kg per minute, and the effects of low, normal, and high sodium intakes were determined. Significant nitric oxide synthesis inhibition was evidenced by a decrease in the depressor and flow responses to systemic acetylcholine administration. During the normal sodium intake plus nitro-arginine period, arterial pressure increased to hypertensive levels, averaging 120 +/- 4% of control; renal vascular resistance increased to an average of 134 +/- 8% of control; glomerular filtration rate and renal plasma flow decreased to 83 +/- 3% and 81 +/- 3% of control, respectively; and no changes occurred in filtration fraction, plasma renin activity, plasma concentrations of aldosterone and cortisol, urinary sodium excretion, sodium balance, fractional excretion of sodium, urine volume, and volume balance. Arterial pressure increased further to 130 +/- 3% of control during high salt intake, and sodium balance was achieved at each sodium intake despite the increase in arterial pressure because of a hypertensive shift in the relation between urinary sodium excretion and arterial pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldosterone↗
PubMed1994

Mechanisms involved in the cardiovascular-renal actions of nitric oxide inhibition.

The roles of the sympathetic nervous system, angiotensin II, and arginine vasopressin in the cardiovascular-renal responses to nitric oxide synthesis inhibition were examined in eight conscious dogs equipped with arterial and venous catheters and a nonoccluding bladder catheter. Nitric oxide inhibition was achieved by intravenous infusion of NG-nitro-L-arginine methyl ester (L-NAME) at 37.1 nmol/kg per minute for 140 minutes in the control group. The same dogs, after a 1-week recovery, were pretreated for 2 days with either prazosin for alpha 1 blockade, prazosin plus propranolol for alpha 1 plus beta blockade, L-158,809 for angiotensin receptor blockade, or d(CH2)Tyr(Me)arginine vasopressin for vasopressin-V1 blockade, and the L-NAME infusion was repeated. After 140 minutes of L-NAME infusion into the control group, mean arterial pressure and renal vascular resistance had increased 16% and 71%, and renal blood flow, glomerular filtration rate, urine flow, and urinary sodium excretion had decreased 33%, 16%, 61%, and 64%, respectively. The decrement in renal blood flow and glomerular filtration during L-NAME administration was unaffected by any of the neurohumoral blockers. During V1 blockade L-NAME resulted in only a 3% increase in arterial pressure, attenuation of the renal vascular resistance response, and almost total elimination of the decrease in urine flow. During angiotensin blockade the L-NAME-induced increase in arterial pressure was markedly attenuated, and the decrease in urinary sodium excretion was attenuated in the alpha 1 plus beta blockade group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Reinfection with Schistosoma japonicum after treatment with praziquantel in Poyang lake region, China.

The study on reinfection with Schistosoma japonicum after treatment was carried out in a cohort of subjects in a heavy endemic village of Poyang lake region, China. After mass treatment with praziquantel in non-transmission time, detailed observations of water contact were estimated using the mean area of skin exposed daily. One year after treatment, the prevalence of infection in study subjects was 54.48%, returning to 83% of initial prevalence. The peak prevalence occurred the 11-15 year age class, but intensity of exposure also varies with age and that age group supporting the higher prevalence of reinfection had high levels of exposure. Among groups of subjects with a similar exposure stratum, young subjects under the age of 21 years were more heavily reinfected, while no heavy reinfection was observed in adults (> or = 25 years). These observations suggest that subjects in this area slowly acquire an increasing degree of immunity to lighten the intensity of infection with S. japonicum.

Adolescent↗
PubMed1994

[A new natural focus of scrub typhus found in Hunchun].

From May to June 1992, Apodemus agrarius and Apodemus speciosus were captured in Hunchun, Jilin Province. Four strains of Rickettsia tsutsugamushi were isolated from viscera of rats and trombiculid mites. At the same time, the antibody against Rickettsia tsutsugamushi was assayed in the sera of the local people and the wild rats. The positive rates were 15.2% and 16.4%, respectively. The above results showed that a natural focus of scrub typhus exists in Hunchun area.

Animals↗
PubMed1993

Human synaptic proteins with a heterogeneous distribution in cerebellum and visual cortex.

Synaptic pathology is likely to be an important feature of a number of neuropsychiatric illnesses. An antibody called EP10 was used previously to demonstrate a regional reduction in a 38 kDa synaptophysin-like protein in Alzheimer's disease. The SP antibodies were developed for further study of this and other synaptic proteins in human brain. Human brain proteins immunoprecipitated with EP10 were used as the immunogen. Hybridoma screening was carried out with a sequential ELISA-immunocytochemical approach. Sixteen antibodies were obtained, the antigens clustered into five groups. Five antibodies were reactive with a 38 kDa synaptophysin-like protein. Another two antibodies were reactive with a 16 kDa antigen which may be synaptobrevin. Immunocytochemical studies indicated these two antigens appeared to be co-localized in human brain. Four antibodies were reactive with a distinct, 34-36 kDa antigen. In the cerebellum, this antigen was restricted to terminals in the molecular layer, putatively in the parallel fibre synapses. Two antibodies were reactive with a 26-27 kDa antigen. In the cerebellum, this antigen localized to a subset of terminals which included the axo-axonal contacts of the Basket and Purkinje cells. The final group of three antibodies detected a complex group of 38 kDa. 40 kDa and higher molecular weight antigens. The results suggest that heterogeneity among synapses can be defined through antibodies directed against distinct proteins. The SP antibodies may be useful probes for studies of human synaptic proteins, and for studies of pathological conditions which disrupt these molecules.

Animals↗
PubMed1993

The contribution of helical potential to the in vitro receptor binding activity of a neuropeptide Y N-terminal deletion fragment.

In its dimeric form neuropeptide Y (NPY) folds into a compact structure in which the antiparallel oriented proline and alpha-helices apparently associate to form a primitive hydrophobic core. To investigate the contribution of helical stability to the receptor binding activity of NPY and its N-terminal deletion fragments, we synthesized and studied the solution conformational properties and in vitro activities of NPY, N alpha-acetyl-NPY2-36, NPY15-36, N alpha-propionyl-NPY15-36, and N alpha-succinyl-NPY15-36. NPY15-36 is significantly less helical than both NPY and N alpha-acetyl-NPY2-36, and this decreased helical potential is attributed to the absence of the intramolecular stabilizing interaction afforded by the proline helix in the latter analogues. However, in accord with the helix dipole model, the helical potential of NPY15-36 is significantly increased by N-terminal succinylation, whereas propionylation has no effect. In addition to an increase in helical potential, N alpha-succinyl-NPY15-36 is 2.5 and 4.6 times more active than NPY15-36 and N alpha-propionyl-NPY15-36, respectively, and is equipotent with N alpha-acetyl-NPY2-36 in displacing 1 nM [3H]-NPY from specific binding sites in rat brain membranes. The demonstration of a positive correlation between % alpha-helix content and in vitro binding activity suggests that the helical potential of N-terminal NPY deletion fragments contributes to their in vitro activity in the rat brain, and that a second role of the proline helix might be to stabilize the receptor-active conformation of the NPY alpha-helix.

Amino Acid Sequence↗
PubMed1993

Role of nitric oxide in long-term angiotensin II-induced renal vasoconstriction.

In vitro studies have indicated that nitric oxide may play an important role in modulating the renal vascular actions of angiotensin II (Ang II). However, the physiological importance of this interaction in the long-term regulation of renal hemodynamics is unknown. Therefore, the goal of this study was to determine if long-term Ang II-induced renal vasoconstriction was potentiated by nitric oxide synthesis inhibition. The intrarenal effects of Ang II were examined in eight unilaterally nephrectomized, conscious dogs before and after systemic inhibition of nitric oxide synthesis. Ang II infusion into the renal artery at 0.5 ng/kg per minute resulted in decreases in renal plasma flow of 15% and 9% after 3 and 5 days, respectively. During this time, glomerular filtration rate decreased 12% after 3 days of angiotensin but was not significantly changed after 5 days. After 4 days of recovery from Ang II, nitric oxide synthesis was inhibited with intravenous NG-nitro-L-arginine-methyl ester (L-NAME) at 10 micrograms/kg per minute for 5 days, and this caused a significant decrease in renal plasma flow but no change in glomerular filtration rate. Infusion of Ang II into L-NAME-pretreated dogs for an additional 5 days further decreased renal plasma flow and glomerular filtration 14% and 11%, respectively. However, the effects of Ang II and L-NAME on renal plasma flow were only additive on days 3 and 5 of this period, and the effects on glomerular filtration were additive on day 3 but were potentiated on day 5.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1993

Cardiovascular responses to long-term blockade of nitric oxide synthesis.

The goal of this study was to determine if there is a basal release of nitric oxide that affects long-term arterial pressure regulation in dogs. Studies were conducted over a 23-day period in eight conscious dogs with indwelling catheters. Nitric oxide synthesis was blocked by continuous intravenous infusion of nitro-L-arginine-methyl ester at 37.1 nmol/kg per minute for 11 days. Arterial pressure increased to 120 +/- 4% of control on the first day, decreased for a few days, and then increased to a maximum value of 122 +/- 6% of control on day 7. Bradycardia was sustained throughout the entire nitro-arginine period. Blockade of nitric oxide synthesis was evidenced by attenuated pressure and flow responses to systemic acetylcholine infusion. The pressor response to phenylephrine was increased for only 1 day, and the hypotensive effects of nitroprusside were enhanced. Also, the variability of arterial pressure was significantly increased during nitro-arginine. Sodium and water balances were positive the first day of nitro-arginine infusion but were unchanged for the entire nitro-arginine period. In conclusion, the data suggest that blockade of the basal release of nitric oxide in dogs causes an increase in the long-term level of arterial pressure without any sustained sodium or water retention.

Acetylcholine↗
PubMed1993

[Study on analysis of peimisine in bulbus fritillariae by HPLC].

A new method for the determination of peimisine in bulbus Fritillariae by ion-pair HPLC has been developed. The chromatographic system consists of ODS column and mobile phase of methanol--water (69:31) containing 7.5 mmol/L of SDS (pH 4.5 +/- 0.1). Twelve samples of different species in the family of Fritillaria have been analyzed by this method. The results show that all samples contain peimisine and the contents of peimisine are correlative to those of total alkaloids.

Alkaloids↗