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Biomedical subjects

J Tang

Publications and source records attributed to J Tang.

At least 649 records · Page 36Linked to original sources
PubMed1970

Amino acid sequences around the disulphide bridges and methionine residues of porcine pepsin.

1. The amino acid sequences around three disulphide bridges and four methionine residues of porcine pepsin were studied by using diagonal electrophoresis methods. 2. Two of the three disulphide bridges were in small loops of five and six residues. The sequence around one of the two half-cystine residues of the third disulphide bridge had a large number of acidic residues. 3. The sequence of a tetrapeptide containing phosphoserine was also determined. 4. Four unique methionine-containing sequences were constructed. The information is sufficient for the determination of the overlaps in the cyanogen bromide fragments of pepsin. 5. The usefulness of diagonal methods in the study of protein structure, the relative positions of cystinyl and methionyl residues in porcine pepsin and the homology between pepsin and rennin are discussed.

Amino Acid Sequence↗
PubMed1967

A diagonal electrophoretic method for selective purification of methionine peptides.

1. A method is described that selectively purifies methionine peptides from enzymic digests of a protein. The peptides, after paper electrophoresis, are treated on paper with iodoacetamide at acid pH. This specifically converts methionine residues into their sulphonium salts. When the paper is submitted to electrophoresis at right angles to the original direction, the carbamoylmethylmethionine peptides emerge from an undifferentiated diagonal. 2. Heating at neutral pH converts carbamoylmethylmethionine into homoserine and thereby specifically cleaves the peptides. 3. The effect of the modifications on amino acid composition and sequence analyses of the peptides was studied. 4. When the method was applied to a tryptic digest of S-aminoethyl-chymotrypsinogen A, two peptides were selectively purified that had the expected amino acid sequence.

Alkylation↗
PubMedDate not supplied

Distribution of met5-enkephalin-Arg6-Phe7 (MEAP) in various tissues of rats and guinea pigs.

With a specific and sensitive radioimmunoassay coupled to HPLC separation, we have measured met5-enkephalin-Arg6-Phe7 in extracts of various peripheral organs. The highest content was found in ileum and lung. The MEAP in lung can be released in a Ca++-dependent manner by KCl. The ratio of MEAP/ME seems to differ in various peripheral tissues, suggesting that MEAP may not only be a precursor of ME but may also act as a neurotransmitter or neuromodulator itself.

Animals↗
PubMedDate not supplied

Characterization and localization of atriopeptin in rat atrium.

An antiserum specific for atriopeptin was used to characterize and localize atriopeptin-like immunoreactive material in rat atrium by radioimmunoassay and immunohistochemical techniques. The antiserum recognizes atriopeptin I, atriopeptin III, and alpha-human atrial natriuretic polypeptide, but does not recognize met-enkephalin, cholecystokinin, dynorphin A, bradykinin, substance P, or beta-endorphin. A high content of atriopeptin was found in crude extracts of rat atria, as compared to ventricles, and the atriopeptin-like immunoreactive material was found to be located exclusively in granules within atrial cardiocytes. Fractionation of the immunoreactive material by gel filtration and reverse-phase HPLC revealed the presence of multiple atriopeptins.

Animals↗
PubMedDate not supplied

Alpha-human atrial natriuretic polypeptide (alpha-hANP) in normal volunteers and patients with heart failure or hypertension.

The presence of alpha-hANP immunoreactive material in human heart and plasma was investigated with a specific and sensitive radioimmunoassay and immunohistochemical method. It was found that alpha-hANP immunoreactive staining of specific atrial granules was located around the nucleus of atrial cardiocytes. No immunoreactive staining was found in the ventricle. The content of immunoreactive hANP was 0.5 pmol/mg protein in the atria and 0.11 +/- 0.01 pmol/ml in the plasma of 26 normal volunteers. In 16 patients with congestive heart failure and 26 patients with essential hypertension, the plasma level of immunoreactive alpha-hANP was significantly lower than that in normal humans. The above evidence indicate that alpha-hANP is a putative hormone secreted by human atrium. A relative shortage of alpha-hANP in the circulatory system may be involved in the mechanism of heart failure and hypertension.

Atrial Natriuretic Factor↗
PubMedDate not supplied

Optimization of pelvic heating rate distributions with electromagnetic phased arrays.

Deep heating of pelvic tumours with electromagnetic phased arrays has recently been reported to improve local tumour control when combined with radiotherapy in a randomized clinical trial despite the fact that rather modest elevations in tumour temperatures were achieved. It is reasonable to surmise that improvements in temperature elevation could lead to even better tumour response rates, motivating studies which attempt to explore the parameter space associated with heating rate delivery in the pelvis. Computational models which are based on detailed three-dimensional patient anatomy are readily available and lend themselves to this type of investigation. In this paper, volume average SAR is optimized in a predefined target volume subject to a maximum allowable volume average SAR outside this zone. Variables under study include the position of the target zone, the number and distribution of radiators and the applicator operating frequency. The results show a clear preference for increasing frequency beyond 100 MHz, which is typically applied clinically, especially as the number of antennae increases. Increasing both the number of antennae per circumferential distance around the patient, as well as the number of independently functioning antenna bands along the patient length, is important in this regard, although improvements were found to be more significant with increasing circumferential antenna density. However, there is considerable site specific variation and cases occur where lower numbers of antennae spread out over multiple longitudinal bands are more advantageous. The results presented here have been normalized relative to an optimized set of antenna array amplitudes and phases operating at 100 MHz which is a common clinical configuration. The intent is to provide some indications of avenues for improving the heating rate distributions achievable with current technology.

Combined Modality Therapy↗
PubMedDate not supplied

Hemodynamic effects of centrally administered adrenomedullin (13-52) in anesthetized rats.

This study was conducted to investigate the effect of intracerebroventricular administration of adrenomedullin (13-52) [ADM(13-52)], a novel hypotensive peptide, on the hemodynamic parameters of anesthetized rats. ADM(13-52) was administered centrally in a dose of 0.4-3.2 nmol/kg. It provoked marked, prolonged and dose-dependent increases in mean arterial blood pressure, heart rate, stroke volume, cardiac index, left ventricular pressure, left ventricular dp/dtmax and dp/dtmin, but reduction in total peripheral resistance index. In addition, intracerebroventricular administration of ADM(13-52; 1.6 nmol/kg) provoked a marked increase in renal sympathetic nerve activity. Intracerebroventricular administration of artificial cerebrospinal fluid had no effect on the hemodynamic parameters and renal sympathetic nerve activity. The results indicate that ADM(13-52) exerts a central action on the cardiovascular system. The mechanisms of hemodynamic changes induced by central ADM(13-52) were preliminarily analyzed in this study. ADM might play a role in the central control of the cardiovascular system, although the confirmed mechanisms and the physiological implications are undetermined.

Adrenomedullin↗
PubMedDate not supplied

Bone sialoprotein promotes bone metastasis of a non-bone-seeking clone of human breast cancer cells.

Bone sialoprotein (BSP) is a major non-collagenous protein in mineralized tissues. BSP is also implied to be involved in tumor metastasis through its unique structure. Using the human breast cancer cell line MDA-231, we established both brain-seeking and bone-seeking cell clones. The brain-seeking cells (MDA4-231BR) showed no bone metastasis in an animal model. In this experiment, MDA-231BR cells were transfected with BSP cDNA and inoculated into the hearts of nude mice. All five nude mice which received BSP-transfected MDA-231BR cells developed bone metastases, while no bone lesions were observed in the control group. Histological examination revealed invasion of tumor cells into the endosteal space and erosion of the bone margin. Some animals were crippled due to large lesions. These results suggest that BSP may impart to breast cancer cells the capacity to metastasize and thus play an important role in bone metastasis of malignant tumors.

Animals↗
PubMedDate not supplied

[Hemorrhagic pseudo-cyst of the pancreas caused by erosion of the gastroduodenal artery during chronic calcifying pancreatitis].

A hemorrhagic pseudo cyst of pancreas, due to a gastro duodenal artery erosion, is presented in a patient presenting a chronic pancreatitis. The diagnosis was suspected by means of clinical, ultrasound, TDM signs and was confirmed by coeliomesenteric angiography. The surgical treatment was successfully performed by local hemostasis and cystojejunal Roux-loop anastomosis.

Arteries↗
PubMedDate not supplied

[Duodenocaval fistula. Apropos of a case. Clinical case].

Among entero-vascular fistulae, the duodenocaval type is exceptional. A case arising in a patient operated 10 months ago from a right kidney cancer, is reported. The clinical feature associated a septicemia to an intestinal hemorrhage. The diagnosis of entero-vascular fistula was performed at the operating time. In the world literature only 8 cases of duodeno-caval fistulae have been previously reported. The injury of duodenocaval area is the most frequent etiology of the communication causing moderate digestive hemorrhage and understood septicemia. The imaging explorations may suspect the diagnosis that is confirmed baparotomy. The treatment is always a surgical one: closure of digestive fistula by intestinal patch and suture of vascular defect. The prognosis depends on experience and skill of the surgeon and remains serious.

Aged↗