Leptin is a metabolic signal to the reproductive system

Leptin, a newly-discovered hormonal product of the obese (ob) gene, is expressed by adipocytes and thought to play a role in the regulation of food intake and metabolism. We tested the hypothesis that leptin signals metabolic information to the reproductive system by examining its effects on the reproductive system of ob/ob mice, which have a congenital deficiency in leptin and are infertile. We treated pair-fed males and females with leptin (50 microg twice daily, ip) or vehicle (n=10/group) for 14 days, after which the animals were bled and killed. Leptin-treated females had significantly elevated serum levels of LH, increased ovarian and uterine weights, and stimulated aspects of ovarian and uterine histology compared to controls. Leptin-treated males had significantly elevated serum levels of FSH, increased testicular and seminal vesicle weights, greater seminal vesicle epithelial cell height, and elevated sperm counts compared to controls. These results demonstrate that leptin stimulates the reproductive endocrine system in both sexes of ob/ob mice and suggest that leptin may serve as a permissive signal to the reproductive system of normal animals.

Apoptosis in the corneal epithelium

PURPOSE

To determine the viability of corneal surface cells and to determine whether apoptosis is present in the corneal epithelium of the rabbit.

METHODS

The viability of epithelial surface cells was examined using a calcein-ethidium assay. In this two-color fluorescence assay, viable cells fluoresce green, and the nuclei of nonviable cells fluoresce red. The number of nonviable cells on the normal corneal epithelial surface was quantified. Surface and shed cells also were examined from shear-stressed corneas. The TUNEL technique (TdT-mediated dUTP nick-end labeling) was used to detect DNA fragmentation characteristic of apoptotic cells.

RESULTS

The calcein-ethidium viability assay revealed that the normal epithelial surface is composed mainly of viable cells, with nonviable cells making up a small percentage of the whole. There was an increase in the density of nonviable cells from the periphery of the epithelial surface to the center, In flatmounts of the cornea, TUNEL labeling demonstrated that a small percentage of surface cells exhibited DNA fragmentation, whereas cross-sections revealed that DNA-fragmented cells were found exclusively on the epithelial surface. Epithelial cells from shear-stressed corneas showed an increased number of apoptotic cells.

CONCLUSIONS

The normal epithelial surface consists mainly of viable cells, with only a small percentage of nonviable cells and apoptotic cells. The results suggest that nonviable epithelial cells are shed after terminal differentiation, whereas viable cells can be shed by classical apoptosis with the formation of blebs. Thus, there appears to be more than one mechanism for removal of cells from the corneal surface.

[Prevention of endotoxic shock in rats with hepatic stimulating substance]

In order to understand the mechanism of prevention of endotoxic shock and evaluate the pathological changes taking place, an animal model of endotoxic shock was established by intravenous injection of endotoxin into rats, which were then treated with a hepatic stimulating substance, hepatopoietin (HPN). The results were as follows; (1) There was coincidence of low blood pressure and high serum level of tumor necrosis factor (TNF) in the experimental rats. (2) Simultaneous intravenous injection of endotoxin and introperitoneal injection of HPN showed that HPN can prevent the drop of blood pressure, lower the TNF level and ameliorate the tissure injury in lungs and kidneys induced by endotoxin. If HPN was given 15 minutes ofter injection of endotoxin, the drop of blood pressure could not be prevented and the TNF level remained high. It is suggested that TNF is an important mediator for endotoxic shock and treatment of endotoxic shock might be effective, if it is intituted early.

Separate promoters in the human A1 adenosine receptor gene direct the synthesis of distinct messenger RNAs that regulate receptor abundance

There are two types of transcripts for the human A1, adenosine receptor. They are expressed in a tissue-specific manner in human tissues and contain distinct exons. Previously, it had appeared that the two transcripts may have occurred through alternative splicing. The transcript beta has two upstream AUG codons, which in transiently transfected COS-7 cells leads to a reduced level of receptor expression. When genomic sequence including sequences 5' to transcriptional start site, exon 1A, intron 1A, exon 1B, intron 1B, exon 2, and coding sequence was inserted into an expression vector (pCMV5/huA1), the resulting transcripts had the same overall structure as the transcripts present in human tissues. Primer extension and 5' rapid amplification of cDNA ends of mRNA from transfected cells revealed the transcription start sites for these two transcripts occurred in what previously had been termed introns. These results were confirmed with similar analysis of mRNA derived from human tissues. Two nonconsensus putative TATA boxes (TTAAGA and TTTAAA) are located upstream of the transcription start sites for transcripts alpha and beta. When the TATA boxes and their flanking sequences were fused to a firefly luciferase gene containing promoterless vector, both demonstrated strong promoter activity in Chinese hamster ovary cells. Promoter A directs the synthesis of transcript alpha, and promoter B directs the synthesis of transcript beta. Promoter A contains a series of AGG elements between the putative TATA box and the transcription start, which accounts for a major portion of the promoter activity based on deletion and mutation analysis. In general, promoter A is more active than promoter B in transfected cells. The nonconsensus TATA box in promoter B plays a more important role in promoter activity than the TATA box in promoter A. The human A1 adenosine receptor gene appears to use two separate promoters to direct synthesis of distinct transcripts, which can then regulate the relative abundance of A1 adenosine receptor in tissues. We have redefined the human A1 adenosine receptor gene structure based on these new data.

NMR identification of calcineurin B residues affected by binding of a calcineurin A peptide

Triple resonance 3D NMR methods have been used to study the interaction between calcineurin B and a peptide fragment of calcineurin A for which it has high affinity (KD approximately 4 x 10(-7) M). Although calcineurin B aggregates at NMR concentrations of approximately 1 mM, in the presence of a target peptide fragment of calcineurin A it becomes monomeric and yields NMR spectra that are very similar to those reported previously for calcineurin B solubilized by the zwitterionic detergent CHAPS. Changes in chemical shifts between CHAPS- and peptide-solubilized calcineurin B are small which is indicative of no differences in secondary structure. Residues most affected by binding to target peptide are found primarily on the hydrophobic faces of the four helices, present in each of the two globular domains in calcineurin B, and in the loops connecting helices II and III, IV and V, and possibly in the C-terminal 12 residues, which also exhibit a change in mobility.

Human adenosine A1 receptor gene: systematic screening for DNA sequence variation and linkage mapping on chromosome 1q31-32.1 using a silent polymorphism in the coding region

Adenosine is a major inhibitory neuromodulator in the central nervous system. One of the receptors mediating the central effects of adenosine is the adenosine A1 receptor. We performed a systematic mutation scan of the coding region of the adenosine A1 receptor gene to explore its variability in the general population. Investigating 40 unrelated healthy subjects by single-strand conformation analysis no sequence changes of likely functional relevance were observed. We detected, however, a frequent T to G substitution at nucleotide position 716 which constitutes the first variant described in an adenosine receptor gene. It was used for fine scale linkage mapping of the A1 gene. Employing a polymerase-chain-reaction-based restriction assay, we genotyped 7 CEPH families (Centre d'Etude du Polymorphisme Humaine) and mapped the receptor in a gene cluster around the renin gene on chromosome 1q31-32.1. In addition, we utilized the 716T/G polymorphism to demonstrate biallelic expression of the adenosine A1 receptor gene in adult human brain.

Solution structure of calcium-free calmodulin

The three-dimensional structure of calmodulin in the absence of Ca2+ has been determined by three- and four-dimensional heteronuclear NMR experiments, including ROE, isotope-filtering combined with reverse labelling, and measurement of more than 700 three-bond J-couplings. In analogy with the Ca(2+)-ligated state of this protein, it consists of two small globular domains separated by a flexible linker, with no stable, direct contacts between the two domains. In the absence of Ca2+, the four helices in each of the two globular domains form a highly twisted bundle, capped by a short anti-parallel beta-sheet. This arrangement is qualitatively similar to that observed in the crystal structure of the Ca(2+)-free N-terminal domain of troponin C.

A comparison of the effects of the propofol versus midazolam during total intravenous anesthesia for gynecological surgery procedures

The effects of propofol and midazolam as an intravenous anesthetic were compared in 40 ASA I-II patients undergoing gynecological surgery during total intravenous anesthesia (TIVA). They were divided into propofol group (P n = 20) and midazolam group (M n = 20) randomly. The anesthesia was designed for each group respectively. Here, we discuss the experimental method and the results, which indicate that propofol is not only an effective anesthetic but also has more rapid and head-clear recovery properties than midazolam.

[Expression of 12 antibody escape mutants of hepatitis B virus surface antigen gene in mammalian cell by using an Epstein-Barr based vector]

A 900bp DNA fragment of hepatitis B virus surface antigen gene by digesting BamHI and HpaI sites on the open reading frame of HBV DNA on plasmid pEcob6 containing double copes of HBV DNA was cloned into SmaI site on the phagmide vector pBluescribt SK +. From this recombinant vector, 12 hepatitis B virus surface antigen gene mutants were obtained by oligonucleotide-mediated site directed mutagenesis. The expression vector-pMEP4HBS mutants are constructed by sub-cloning all of these mutant fragments of hepatitis B virus surface antigen gene on pBluescritSK+HBSM into BsmHI and KpnI sites on an Epstein-Barr virus based on eukaryotic expression vector-pMEp4. The vector pMEp4HBSMs were transfected to human hepatocellular carcinoma cell line-HepG2 by calcium phosphate mediated transfection, and resistant cell clones were obtained 3 weeks after selecting by hygromycine B. The results of detection of HBsAg excreted by resistant cell clones with monoclonal antibody to HBsAg showed that all antibody escape mutants of HBsAg except mutant 145R, a substitution of arginine for glycine at amino acid 145 position in HBsAg, were positive.

Corneal epithelial fluorescein staining

BACKGROUND

There is some difference of opinion in the literature about the nature of fluorescein staining of the epithelial surface. Most authors support the view that fluorescein staining is due to drop out of cells and pooling of fluorescein in the footprint. Others believe that fluorescein fills intercellular spaces. Others suggest that cells themselves stain with fluorescein.

METHODS

Rabbit corneas were stained with fluorescein and examined with the biomicroscope and later with a higher magnification epifluorescent microscope following excision.

RESULTS

Fluorescein staining was shown to be due to staining of individual cells. No evidence was found to support the contention that fluorescein resides in areas of cell drop out, or that staining was due to filling of intercellular spaces. Micropunctate staining is shown to be due to staining of cells in an optimum manner, which is referred to as hyperfluorescence.

CONCLUSIONS

The recognition that fluorescein stains cells, even in the case of epithelial abrasion, allows reinterpretation of many staining phenomena, including "salt and pepper" staining.

Rotational dynamics of calcium-free calmodulin studied by 15N-NMR relaxation measurements

The backbone motions of calcium-free Xenopus calmodulin have been characterized by measurements of the 15N longitudinal relaxation times (T1) at 51 and 61 MHz, and by conducting transverse relaxation (T2), spin-locked transverse relaxation (T1 rho), and 15N-[1H] heteronuclear NOE measurements at 61 MHz 15N frequency. Although backbone amide hydrogen exchange experiments indicate that the N-terminal domain is more stable than calmodulin's C-terminal half, slowly exchanging backbone amide protons are found in all eight alpha-helices and in three of the four short beta-strands. This confirms that the calcium-free form consists of stable secondary structure and does not adopt a 'molten globule' type of structure. However, the C-terminal domain of calmodulin is subject to conformational exchange on a time scale of about 350 microseconds, which affects many of the C-terminal domain residues. This results in significant shortening of the 15N T2 values relative to T1 rho, whereas the T1 rho and T2 values are of similar magnitude in the N-terminal half of the protein. A model in which the motion of the protein is assumed to be isotropic suggests a rotational correlation time for the protein of about 8 ns but quantitatively does not agree with the magnetic field dependence of the T1 values and does not explain the different T2 values found for different alpha-helices in the N-terminal domain. These latter parameters are compatible with a flexible dumb-bell model in which each of calmodulin's two domains freely diffuse in a cone with a semi-angle of about 30 degrees and a time constant of about 3 ns, whereas the overall rotation of the protein occurs on a much slower time scale of about 12 ns. The difference in the transverse relaxation rates observed between the amides in helices C and D suggests that the change in interhelical angle upon calcium binding is less than predicted by Herzberg et al. Strynadka and James [Strynadka, N. C. J. & James, M. N. G. (1988) Proteins Struct. Funct. Genet. 3, 1-17].

Diagnosis and surgical treatment of bronchogenic cysts

Between 1974 and 1993, 22 patients with bronchogenic cysts were operated on in our hospital; there were 14 men and 8 women, ranging in age from 11 to 62 years. The cyst locations were mediastinal in 13 (59.1%) and intrapulmonary in 9 (40.9%). There were symptoms (chest pain and recurrent bronchiolitis) in 20 patients (91%). The preoperative complications included infection in the lung and in the cyst and dysphagia due to esophageal compression. Chest pain was the main symptom in mediastinal cyst and recurrent infection of lung in intrapulmonary cyst. Plain chest radiograms showed that a round shadow, occasional air-fluid levels, and peripheral calcification may be found in cysts. An operation is the best treatment for cysts. All cysts were completely excised. No postoperative complications, late complications, or recurrence developed in our patients.

Adenosine receptors: protein and gene structure

Adenosine produces a wide variety of effects throughout the body via activation of cell surface adenosine receptors. Adenosine receptors belong to the family of seven transmembrane domain G protein-coupled receptors and four subtypes have been cloned from a variety of species: the A1AR, A2aAR, A2bAR and A3AR. With a knowledge of both the protein sequence of adenosine receptors and the structure of the A1AR gene, the function and regulation of these receptors can be further explored. Site-directed mutagenesis of the A1AR has resulted in the identification of amino acid residues in transmembrane domains 6 and 7 that are critical in both agonist and antagonist binding. The construction and analysis of A1/A3 chimeric receptors has also revealed regions of adenosine receptors important in ligand binding. These include the distal region of the second extracellular loop of adenosine receptors, which has a role in the binding of both agonist and antagonist ligands. A segment of the exofacial portion of the transmembrane domain 5 of adenosine receptors appears to be involved in the selective recognition of agonist ligands containing a substitution at the 5'-position of the ribose moiety. Isolation of the genomic sequence of the human A1AR, in combination with analysis of the transcript distribution in several tissues, indicates that alternative splicing of the human A1AR occurs in the 5'-untranslated region of the gene. Two distinct transcripts, containing either exons 3, 5 and 6 or exons 4, 5 and 6, exist with exons 3 and 4 apparently mutually exclusive. The exon 4, 5 and 6 transcript has been detected in all tissues that express the A1AR, while the exon 3, 5 and 6 mRNA is found in tissues that display a relatively high A1AR expression. Findings suggest that the presence of two ATG codons in exon 4, upstream of the translation start site, is involved in the repression of the A1AR expression in those tissues containing the exon 4, 5 and 6 transcript.

A clinical analysis of 38 patients with primary tracheo bronchial tumors

During a 17-year period, 38 patients with primary tracheobronchial tumors received surgical treatment in PUMC Hospital. Among the 38, 12 had low-malignancy tracheal tumors, 11 had benign tracheal tumors, 14 had low malignancy bronchial tumors and 1 had a benign bronchial tumor. Fifteen operations were performed on 12 patients with low-malignancy tracheal tumors, including local resection of the tumor and tracheal wall in 4 and curettage of the tumor plus electrical cauterization in 10. Postoperative radiotherapy was used as an adjuvant treatment in 8 patients with adenocystic carcinoma. Eight patients have survived for more than 5 years and 3 patients have survived for longer than 10 years postoperatively. All 11 patients with benign tumors received curettage of the tumor and were followed up for an average of 6.5 years. Among them, 9 are still alive. Of the 14 patients with low malignancy bronchial tumors, 5 underwent curettage of the tumor plus electrical cauterization through incision of the main bronchus or intermedial bronchus, and 7 underwent lobectomy or pneumonectomy. The authors conclude that the correct diagnosis rate can be increased by enhancing recognition of this disease and applying tracheal tomography and bronchoscopy.

Comparative observations on the types of atrophic gastritis and biopsy pathology of gastric mucosa

300 cases of chronic atrophic gastritis were classified into 3 types of qi-deficiency of spleen and stomach, yang-deficiency of spleen and stomach, and yin-deficiency of spleen and stomach according to syndrome differentiation of traditional Chinese medicine. The biopsy specimens of gastric mucosa were examined histopathologically and for the presence of pyloric spirobacteria. The results showed that the type of yin-deficiency was the most serious in the degree of pathologic changes, or the glandular atrophy and the interstitial inflammatory cellular infiltration, while the rate of pyloric spirobacteria presence was comparable in all types.

[The clinical characters and treatment of lung cancer in youth]

From January 1970 to December 1990, 67 patients with lung cancer aged younger than 40 years, were treated in the PUMC Hospital. There were 43.3% with SCLC and 37.3% with adenocarcinoma. Twenty-eight patients underwent resection of the lung. Thirty-five cases received chemotherapy or radiotherapy only. The clinical and pathological characteristics of lung cancer in youth, and the influence of surgical and non=surgical treatments to the patients with lung cancer are discussed. The authors consider that the bronchoscopic and sputum smear examinations are very helpful for diagnosing lung cancer in the early stage. Postoperative adjuvant chemo- and radio-therapy is suggested because of the high incidence of SCLC and adenocarcinoma in the young patients with lung cancer.

[Analysis of the influence factors on the resection and prognosis of thymic tumors]

One hundred eleven thymic tumors were intervened surgically, including 92 thymoma, 8 thymic carcinoid, and 10 thymic carcinoma. In this series 50.9% of the cases were complicated with various syndrome, 44.5% with myasthenia gravis (MG), more frequently in the epithelial cell type. Pure red cell aplasia often associated with the spindle-cell thymoma. Of the thymic carcinoid 50% had ectopic ACTH syndrome. Resection rate correlated with the size and invasion of the tumor. There were significant difference in resection rate among thymoma, thymic carcinoid, and thymic carcinoma. The degree of invasion undoubtedly influenced on resection. The 3-, 5-, and 10-year survival rates of the thymoma were 82.7%, 68.1% and 40.0% respectively. The prognosis depended on the pathological classification and the severity of neighbouring invasion, but MG had no significant effect on prognosis. Recurrence and metastasis of the tumor remained to be the main cause of late death.

Characterization of the lanthanide ion-binding properties of calcineurin-B using laser-induced luminescence spectroscopy

Calcineurin (CaN) is a Ca2+/calmodulin-dependent protein phosphatase found in brain and other tissues. It is a heterodimer consisting of a catalytic subunit (CaN-A) and a Ca(2+)-binding regulatory subunit (CaN-B). The primary structure of CaN-B indicates that it, like calmodulin, is an EF-hand protein and binds four Ca2+ ions. Eu3+, due to its favorable spectroscopic and chemical properties, has been substituted for Ca2+ in CaN-B to determine the metal ion-binding properties of this "calmodulin-like" protein. Excitation of the 7F0-->5D0 transition of Eu3+ results in a spectrum similar to that of calmodulin, consisting of three peaks. Analysis of the spectral titration curves reveals four Eu(3+)-binding sites in CaN-B. The affinities vary: sites I and II have dissociation constants of 1.0 +/- 0.2 and 1.6 +/- 0.4 microM, respectively; the values for sites III and IV are Kd = 140 +/- 20 and Kd = 20 +/- 10 nM, respectively. Binding of Tb3+ is slightly weaker. Tb3+ luminescence, sensitized by tyrosine, reveals that for lanthanides the highest affinity sites lie in the C-terminal domain. Energy transfer distance measurements between Eu3+ and Nd3+ in sites III and IV reveal a separation of 10.5 +/- 0.5 A, which suggests that these sites are arranged in a typical EF-hand pair. This information indicates that the overall structure of CaN-B is similar to the dumbbell-shaped proteins troponin-C and calmodulin, but is more like TnC in its metal-binding properties.

The effect of ultraviolet-B irradiation on the cell shedding rate of the corneal epithelium

In this study cell shedding rates of the corneal epithelium were determined in vitro following a single suprathreshold dose of ultraviolet-B irradiation. Rabbit corneas were excised and superfused in pairs. The epithelial and endothelial surfaces were bathed with solutions containing essential ions and adjusted to appropriate pH and osmolality. One cornea in each pair was irradiated, while the other cornea served as a control. Shed cells were periodically collected from the corneal surface and the shedding rate determined by counting the number of cells in a 50 min time period. Following a latent period of about 3 h, the epithelial shedding rate accelerated, and remained elevated for at least 8 h after irradiation. This result suggests that suprathreshold doses of ultraviolet-B irradiation disrupt the normal orderly cell shedding process and homeostatic equilibrium of the corneal epithelium. The elevated cell shedding rate exposes subsurface nerve endings and causes the characteristic pain of photokeratitis.

Posttranscriptional mRNA processing as a mechanism for regulation of human A1 adenosine receptor expression

The human A1 adenosine receptor gene contains six exons with exons 1, 2, 3, 4, and part of 5 representing 5' untranslated regions. Reverse transcription-PCR with exon-specific primers showed two distinct transcripts containing either exons 3, 5, and 6 or exons 4, 5, and 6, with exons 3 and 4 being mutually exclusive. No mature mRNAs containing exons 1 and 2 have been detected. All human tissues that express any A1 receptors contain mRNA with exons 4, 5, and 6. Tissues which express high levels of A1 receptors contain mRNA with exons 3, 5, and 6. Exon 4 contains two upstream ATG codons whereas exon 3 contains none. COS cells transfected with expression vectors containing exon 4 (exons 1-6, 3-6, or Ex4-6) express much lower levels of A1 receptors than vectors without exon 4 (exons 3, 5, and 6). Mutation of upstream ATG codons in exon 4 leads to 3- to 7-fold increased A1 receptor expression, up to the level seen with the construct containing exons 3, 5, and 6. Thus, in human tissues "basal" levels of A1 receptors can be expressed by use of mRNA containing exons 4, 5, and 6, but when high levels are needed, alternative transcripts with exons 3, 5, and 6 are produced.