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Biomedical subjects

J Peters

Publications and source records attributed to J Peters.

At least 397 records · Page 22Linked to original sources
PubMed1992

Transgenic rats carrying the mouse renin gene--morphological characterization of a low-renin hypertension model.

Transgenic rats [TGR; strain name TGR(mRen2)27] harboring the mouse Ren-2 renin gene have been recently generated as a model for the study of primary hypertension that offers the advantage of a clearly-defined genetic alteration. Expression of the mouse Ren-2 gene causes severe hypertension (200 to 260 mm Hg) which is responsive to converting enzyme inhibitors. Compared to control transgene-negative littermates, plasma renin and angiotensin II values are lowered in TGR, whereas plasma prorenin values are strongly elevated. The adrenal gland in TGR shows marked overexpression of mouse renin messenger RNA; in situ hybridization using a 35S-labelled mouse-renin RNA probe reveals that enhanced renin expression is mainly localized to cells of the zona glomerulosa and outer zona fasciculata. Immunohistochemically, renin protein in the TGR adrenal gland is stored in larger quantities than in controls. Adrenal transgene expression probably accounts for most of the elevated plasma prorenin level in TGR, since bilateral adrenalectomy (ADX) causes a significant decrease in prorenin level (318 +/- 79 ng angiotensin I/ml/hr before ADX to 70 +/- 43 ng 4 days after ADX, P less than 0.0005). In the kidney, renin synthesis is almost completely suppressed in TGR. In situ hybridization demonstrates that few juxtaglomerular afferent arterioles express renin. Immunohistochemically, the TGR kidney shows significantly reduced renin and angiotensin II immunoreactivity at the afferent arteriole. Ultrastructural analysis of the afferent arteriolar wall frequently shows the complete absence of renin secretory granules since the granular cells are mostly converted into smooth muscle cells. Beginning at an age of approximately four to six months, TGR develop hypertension-related alterations and pathological lesions in various tissues. In the kidney, the wall thickness of arterioles and arteries is strongly increased, and glomerular lesions including different stages of sclerosis are observed. The thoracic aorta displays a considerable increase in tunica media thickness due to both myocyte hypertrophy and interstitial fibrosis. Coronary arteries and arterioles of the heart are thickened and perivascular fibrosis is observed. The data show that TGR(mRen2)27 transgenic rats display all typical characteristics of hypertensive pathology, making them an interesting model for therapeutic interventions. The fact that these changes occur in animals with a single gene difference to normotensive rats makes them a particularly suitable model for studies on gene-related hypertensive processes.

Adrenal Glands↗
PubMed1992

Chemotherapy with MACOP-B and VACOP-B for intermediate- and high-grade non-Hodgkin's lymphoma: clinical results and analysis of prognostic factors.

Eighty-three previously untreated patients with aggressive non-Hodgkin's lymphomas were treated with either MACOP-B (23 patients) or VACOP-B (60 patients) as originally described by Klimo and Conners [1, 2]. Their median age was 46 years. Thirty-seven patients had stage I or II and 46 stage III or IV disease. The tumor histopathology was reviewed in all cases. Sixty-five patients had intermediate grade and 18 high-grade non-Hodgkin's lymphomas according to the International Working Formulation. The rate of complete response was 74% for MACOP-B and 76% for VACOP-B. At the time of analysis the duration of follow-up was 50 months for the MACOP-B and 22 months for the VACOP-B group. The actuarial three-year progression-free survival was 35 +/- 10% for the MACOP-B group, 48 +/- 11% for the VACOP-B group, and 46 +/- 7% for all patients. Treatment mortality was 6%. A univariate and a multivariate analysis of selected pretreatment parameters and of regimen demonstrated that stage III or IV, high-grade lymphoma, and elevated serum LDH, but not the type of regimen, are significantly associated with poor progression-free survival in our patient population.

Adolescent↗
PubMed1992

mGK-6-derived true tissue kallikrein is synthesized, processed, and targeted through a regulated secretory pathway in mouse pituitary AtT-20 cells.

mGK-6-derived true tissue kallikrein was shown to be synthesized in mouse pituitary AtT-20 cells. This cell line, which is capable of processing other prohormones, only partially processed the proform of kallikrein to its active form, secreting it predominantly as the proform. The secretion of the active form was stimulated in response to a secretagogue, 8-bromo-cyclic AMP. These results imply that not only cellular elements capable of directing the processing of the proform to the active form and the intracellular transport of the kallikrein, but also a pathway that regulates the release of the active form may be present in the AtT-20 cells, thus the availability of this cell line for investigation of biosynthetic and secretory processes for tissue kallikrein in vivo being suggested.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1992

Transcutaneous cardiac pacing in patients with automatic implantable cardioverter defibrillators and epicardial patch electrodes.

In patients with automatic implantable cardioverter defibrillators, insulation of the epicardial patch electrodes (patches) prevents externally applied current from passing through the electrode to the cardiac muscle so that external transthoracic and even internal defibrillation can be unsuccessful. Because emergency cardiac pacing may be required in such a case, a study was performed to evaluate whether, and at what threshold and electrode orientation, transcutaneous pacing is possible in patients with implanted patches. Thresholds for transcutaneous pacing were determined during general anesthesia in nine patients with patches sewn across the heart (anterior right and posterior left ventricles) either before or after surgery, or at both times (automatic implantable cardioverter defibrillator implantation/exchange with or without coronary artery bypass grafting). Because surgery per se can increase the pacing threshold, nine patients of similar body size and weight undergoing routine coronary artery bypass grafting also were evaluated and served as a control group. Pacing thresholds (stimulus duration: 50 ms) were determined during normothermia with a transportable transcutaneous pacer, and adult cutaneous electrodes were placed across the patients' chest in the standard anteroposterior and right-to-left orientations. In all patients with patch electrodes, antero-posterior pacing was possible at a mean threshold of 73 +/- 30 mA standard deviation (range: 40-140 mA). This threshold was not significantly different (Mann-Whitney test) from that in control patients before (57 +/- 20 mA; range: 30-90 mA) or after (94 +/- 24 mA; range: 40-120 mA) coronary artery-bypass grafting. The surgical procedure per se significantly increased the threshold (Wilcoxon test, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Pacing, Artificial↗
PubMed1992

Basic methodology in the molecular characterization of genes.

PURPOSE: During the past two decades, molecular biology techniques have had an increasing impact upon hypertension research. This article will thus review the basic methodology in this field. CONTENTS: Protocols are described for the establishment of a genomic library and its use for the cloning of specific genes, as well as methods for the detection and sequencing of DNA. In addition, techniques to detect and quantify specific messenger RNA, such as Northern blotting, ribonuclease protection assay and in situ hybridization, and the reporter gene approach for the analysis of regulatory gene sequences, are included. The polymerase chain reaction which, as a newly established technique to detect and amplify DNA, has exerted a strong influence upon all areas of molecular biology is the subject of the concluding paragraph. CONCLUSIONS: Molecular biology techniques may be of substantial help in revealing the cause of hypertension and developing tools to prevent and treat this disorder.

Animals↗
PubMed1992

Coronary and systemic vascular response to inspiratory resistive breathing.

To evaluate the coronary and systemic cardiovascular response to graded inspiratory resistive breathing, seven dogs were studied 2-4 wk after chronic instrumentation to measure circumflex coronary artery and ascending aortic blood flows as well as aortic and left ventricular (LV) blood pressures. The experiments were performed under chloralose anesthesia (to exclude any confounding emotional effects by dyspnea on cardiovascular variables) and hyperoxic conditions (to prevent chemoreflex activation by hypoxemia). In a randomized fashion, the dogs were subjected to graded inspiratory resistive breathing (spontaneous breathing alone and moderate and severe resistive loading, corresponding to resistances of approximately 0, 40, and 110 cmH2O.s.l-1, respectively). Each run lasted 10 min. Compared with mechanical ventilation with the respiratory muscles at rest, spontaneous breathing alone and moderate and severe inspiratory resistive loading induced pronounced and significant increases in circumflex coronary blood flow (19, 32, and 62%, respectively), which were almost exclusively accounted for by significant decrements in coronary vascular resistance and were paralleled (r = 0.88, P less than 0.0001) by significant increments (18, 31, and 57%) in heart rate transmural-aortic pressure product, an indicator of LV myocardial O2 demand. An increase in myocardial O2 consumption during resistive breathing was confirmed by analysis of coronary sinus blood samples in additional experiments (n = 3). Cardiac output significantly increased (10, 14, and 35%) because of increases in heart rate (15, 24, and 49%), with LV stroke volume and diastolic dimensions remaining unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1992

ECG-synchronized thoracic vest inflation during autonomic blockade, myocardial ischemia, or cardiac arrest.

To evaluate, in the absence of lung inflation, the cardiovascular effects of single and repetitive pleural pressure increments induced by thoracic vest inflations and timed to occur during specific portions of the cardiac cycle, seven chronically instrumented dogs were studied. Reflexes and left ventricular (LV) performance were varied by autonomic blockade, circumflex coronary occlusion (with and without beta-blockade), or cardiac arrest. Single late systolic, but not early systolic, vest inflations significantly increased LV stroke volume both before (+12.4%) and after myocardial depression by coronary occlusion+beta-blockade (+18.5%) when performed after a period of apnea to control preload and rate. During vest inflations, LV and aortic pressures increased to a greater degree than esophageal pressure (by 51 vs. 39 mmHg, P = 0.0001). Lung inflations (26 trials in 3 dogs) during early or late systole failed to increase stroke volume, despite peak esophageal pressures of 11-26 mmHg. With autonomic reflexes intact, repetitive vest inflations coupled to early systole, late systole, or diastole induced a large (40%) but unspecific systemic flow increase. In contrast, during autonomic blockade, flow increased slightly (7.5%, P < 0.05) with late systolic compared with diastolic inflations but not relative to baseline. During coronary occlusion (with or without beta-blockade), no cycle-specific differences were seen, whereas matched vest inflations during cardiac arrest generated 20-30% of normal systemic flow. Thus only single late systolic thoracic vest inflations associated with large increments in pleural pressure increased LV emptying, presumably by decreasing LV afterload and/or focal cardiac compression. However, during myocardial ischemia and depression, coupling of vest inflation to specific parts of the cardiac cycle revealed no hemodynamic improvement, suggesting that benefits of this circulatory assist method, if any, are minor and may be restricted to conditions of cardiac arrest.

Animals↗
PubMed1992

Role of tissue renin in the pathophysiology of hypertension in TGR(mREN2)27 rats.

A transgenic rat line, TGR(mREN2)27, was established by introducing the murine Ren-2 gene into the genome of rats by microinjection techniques. These rats exhibit severe hypertension, making them an interesting model in which to study the role of renin in the pathophysiology of hypertension. However, although the additional renin gene is the only genetic difference compared with control rats, the exact mechanism of hypertension in TGR(mREN2)27 rats is still unclear. It cannot be attributed to a stimulation of the endocrine renin-angiotensin system or to an overexpression of renin in the kidney, since plasma and kidney renin and renin gene expression in the kidney are low in these animals. Here we describe recent progress made toward elucidating mechanisms of hypertension in TGR(mREN2)27 rats. 1) TGR(mREN2)27 rats were bred to homozygosity. The development of high blood pressure in homozygous rats is accelerated compared with that of heterozygous rats. This is paralleled by a higher mortality rate in homozygous TGR(mREN2)27 rats. Blood pressure and mortality rate of homozygous transgenic rats were effectively reduced by 10 mg captopril per kilogram body weight. 2) Treatment of 8-week-old heterozygous TGR(mREN2)27 rats with 10 mg/kg body wt per day of the angiotensin II receptor antagonist DuP 753 for 4.5 weeks normalized blood pressure. After withdrawal of the drug, blood pressure increased rapidly, reaching control levels after 3 weeks. In another group of TGR(mREN2)27 rats treated with 0.5 mg/kg per day, there was no change in blood pressure. Plasma renin and plasma angiotensin II were significantly higher in the high-dose group compared with the low-dose group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Cortex Hormones↗
PubMed1992

Increased vascular angiotensin formation in female rats harboring the mouse Ren-2 gene.

Rats harboring the mouse Ren-2 transgene develop hypertension despite low levels of plasma renin activity. We tested the hypothesis that these rats exhibit an increase in vascular angiotensin formation caused by the presence of the transgene. We measured the release of angiotensins I and II from isolated perfused hindquarters by high-performance liquid chromatography and radioimmunoassay. Female rats heterozygous for the transgene had significantly elevated mean arterial pressure compared with control rats (189.3 +/- 9.5 versus 110.0 +/- 5.4 mm Hg, p less than 0.05). Plasma angiotensin II was significantly decreased in transgenic rats. Transgenic rat hindquarters released more angiotensin I (121 +/- 37 versus 39 +/- 12 fmol/30 min, n = 7 each) and more angiotensin II (210 +/- 21 versus 62 +/- 12 fmol/30 min, p less than 0.05, n = 7 each) than control rat hindquarters. Captopril increased angiotensin I release and decreased angiotensin II values in both transgenic and control rat hindquarters. Bilateral nephrectomy 24 hours before hindquarter perfusion greatly reduced angiotensin release from control rat hindquarters but not from transgenic rat hind limbs. We also tested for the presence of Ren-2 messenger RNA in mesenteric and aortic tissue by RNase protection assay and Northern blot analysis. We found that Ren-2 messenger RNA was present in mesenteric and aortic tissue of transgenic but not of control rats. We conclude that the Ren-2 transgene is expressed in vascular tissue of transgenic rats and may be responsible for substantial increases in vascular angiotensin formation.

Angiotensin II↗
PubMed1992

The role of the adrenal gland in hypertensive transgenic rat TGR(mREN2)27.

The TGR(mREN2)27 is a new monogenetic rat model in hypertension research. As the mouse Ren-2d renin gene is integrated into their genome, they develop fulminant hypertension between 5 and 15 weeks of age, with blood pressure maxima of 300 mm Hg. Their plasma renin-angiotensin system (RAS) is suppressed, but the transgene is highly expressed in the adrenal gland, so we investigated its possible role in steroid metabolism and the pathogenesis of hypertension. During the phase of hypertension development (between 6-18 weeks), the urinary excretion of deoxycorticosterone (DOC), corticosterone (B), 18-hydroxycorticosterone, and aldosterone is 1.5- to 2.5-fold elevated compared with that in Sprague-Dawley (SD) rats (P less than 0.0005) despite the suppressed plasma RAS. Moreover, the adrenal gland in TGR(mREN2)27 shows an increased maximal response to ACTH stimulation in regard to urinary excretion of DOC (after ACTH, 244 +/- 42 ng/24 h in TGR; 62 +/- 10 ng/24 h in SD; P less than 0.0005) and B (after ACTH, 5144 +/- 346 ng/24 h in TGR; 2607 +/- 324 ng/24 h in SD; P less than 0.0005). Additionally, plasma prorenin in TGR was stimulated more than 10-fold, indicating transgene regulation by ACTH. Since spironolactone treatment did not lower the blood pressure in TGR, hypertension solely due to hypermineralocorticoism is unlikely. Our results indicate that the adrenal steroid metabolism is markedly stimulated in young TGR, and the absolute increase in urinary DOC and B after ACTH injections is enhanced, possibly due to a stimulated local intraadrenal RAS.

18-Hydroxycorticosterone↗
PubMed1992

Zonal distribution and regulation of adrenal renin in a transgenic model of hypertension in the rat.

The hypertensive transgenic rat [TGR (mRen-2)27] is a genetic model of hypertension in which transfection of the Ren-2 mouse renin gene into rats results in severe hypertension. These transgenic rats express a high level of renin in the adrenal gland, and the hypertension is ameliorated by treatment with angiotensin-converting enzyme inhibitors. In this study we investigated the distribution of adrenal renin in the TGR rat and examined the regulation of adrenal renin in a monolayer culture of adrenal cells. High concentrations of active renin and prorenin were found in the adrenal capsular (glomerulosa) and decapsular (fasciculata-medullary) portions of the TGR adrenal. This is in contrast with the Sprague-Dawley (S-D) rat, in which adrenal renin is found mostly in the active form and located primarily in the glomerulosa cells. The zonal distribution of aldosterone was also different in the TGR, with substantial amounts of aldosterone in the zona fasciculata as well as in the glomerulosa, while in the S-D rat, aldosterone is limited to the zona glomerulosa. In the primary monolayer culture of glomerulosa cells, TGR cells had significantly higher levels of active renin and prorenin and showed an increased response to ACTH and high potassium in the medium. Renin activity in the medium was predominantly in the form of prorenin and significantly higher than that in the S-D rat. Cultured fasciculata cells from TGR also produce renin that is stimulated by ACTH, but not by a high potassium concentration. Renin activity in the adrenal homogenate, medium, and plasma from TGR rats was completely inhibited by the renin inhibitor (CP 71362; 1 microM), but only slightly inhibited (12.3 +/- 3%) by a monoclonal antibody that inhibits renin activity from S-D rat tissues by 79.2 +/- 2.5%, suggesting that renin in the plasma and adrenal glands from TGR appears to derive primarily from mouse renin. In conclusion, the TGR (mRen-2)27 rats have higher than normal levels of adrenal renin, and the cultured cells show an exaggerated renin response to ACTH and potassium. The distribution of the renin enzyme in the adrenal zones of the TGR is similar to the distribution of mouse adrenal renin.

Adrenal Glands↗
PubMed1992

Reversibility of airways injury over a 12-month period following smoking cessation.

In this investigation, we examined changes in exfoliated tracheobronchial cells in sputum in 46 individuals (mean age = 49.2 years; mean packyears = 48.7) who discontinued smoking and 37 individuals (mean age = 54.9 years; mean packyears = 65.2) who continued to smoke over a 12-month period after participation in the St. Helena Hospital and Health Center one-week residential smoking cessation program. Before the beginning of the smoking cessation program, those who went on to quit were not different from those who did not quit with respect to baseline cytomorphology ratings. In those individuals with a minimum of three follow-up tests, results indicated significant reductions from precessation levels in macrophages, pigmented macrophages, and neutrophils after adjustment for differences in age, packyears, and pulmonary function (FEV1/FVC). Over the course of follow-up, quitters, in comparison with nonquitters, also had significantly lower mean levels of columnar cells, mucus, mucous spirals, and metaplasia. These results indicate a consistent effect of smoking cessation on cytomorphology and demonstrate that on cessation, some of the measured elements promptly return toward a more normal pattern.

Forced Expiratory Volume↗
PubMed1992

Evidence for tyrosine-linked glycosaminoglycan in a bacterial surface protein.

The S-layer protein of Acetogenium kivui was subjected to proteolysis with different proteases and several high molecular mass glycosaminoglycan peptides containing glucose, galactosamine and an unidentified sugar-related component were separated by molecular sieve chromatography and reversed-phase HPLC and subjected to N-terminal sequence analysis. By methylation analysis glucose was found to be uniformly 1,6-linked, whereas galactosamine was exclusively 1,4-linked. Hydrazinolysis and subsequent amino-acid analysis as well as two-dimensional NMR spectroscopy were used to demonstrate that in these peptides carbohydrate was covalently linked to tyrosine. As all of the four Tyr-glycosylation sites were found to be preceded by valine, a new recognition sequence for glycosylation is suggested.

Amino Acid Sequence↗
PubMed1992

[EBV-lymphadenitis: diagnostic possibilities using immunohistochemistry and in situ hybridization].

EBV infections were studied in paraffin embedded lymph node specimens (n = 20) on DNA, protein, and histological level. The lymph nodes were obtained from 20 patients all testing positive for EBV serologically. The EBV DNA was detected by non radioactive in-situ-hybridisation using the BamHI W fragment of the virus. The EBV latent membrane protein was detected immunohistochemically using the LMP antibody (DAKO). Infected cells were characterized by monoclonal B cell antibodies. By in-situ-hybridization we found positive signals for EBV in all specimens. In contrast, no LMP was detectable immunohistochemically in 2/20 lymph nodes.

Antibodies, Monoclonal↗
PubMed1992

Rapid detection of MYCN gene amplification in neuroblastomas using the polymerase chain reaction.

We have used the polymerase chain reaction (PCR) to detect amplification of the MYCN oncogene in neuroblastoma cell lines and to distinguish primary tumors with a single copy from those with MYCN amplification using DNA extracted from frozen sections. Two primer pairs were used to co-amplify a 428-bp fragment of the MYCN oncogene along with a 268-bp fragment of the beta-globin gene (a single-copy reference standard). After 30 cycles of PCR, the products were resolved by agarose gel electrophoresis. MYCN gene amplification was identified by visual comparison of the relative intensities of MYCN and beta-globin PCR product bands on the ethidium bromide-stained gel. This semiquantitative approach, while inadequate for precise determination of copy number, provided a simple, rapid, nonisotopic method for differentiating tumors with MYCN amplification from those with a single copy. Seventy-four primary tumors were classified as amplified or nonamplified by semiquantitative PCR. Twenty-two of 23 tumors known to carry MYCN gene amplification by Southern analysis were correctly identified by PCR. The single false-negative result was due to a sampling error: DNA was extracted from a block of tissue containing small foci of tumor surrounded by normal tissue. Fifty-one of 51 tumors with a single copy of MYCN were also correctly identified by PCR. We conclude that semiquantitative PCR is a reliable, non-isotopic alternative to Southern blotting for detection of MYCN gene amplification that can be performed rapidly on DNA extracted from frozen sections.

Base Sequence↗
PubMed1992

Nondisjunction of chromosome 21: comparisons of cytogenetic and molecular studies of the meiotic stage and parent of origin.

In the present report, we summarize studies aimed at examining the reliability of chromosome heteromorphisms in analyses of chromosome 21 nondisjunction. We used two cytogenetic approaches--fluorescent in situ hybridization (FISH) to repetitive sequences on 21p and traditional Q-banding--to distinguish chromosome 21 homologues and then compared the results of these studies with those obtained by DNA markers. Using a conservative scoring system for Q-banding and FISH heteromorphisms, we were able to specify the parental origin of trisomy in 10% of cases; in contrast, DNA marker studies were informative for parental origin in almost all cases. The results of the molecular and cytogenetic studies of parental origin concurred in all cases in which assignments were made independently using both techniques. However, in 4 of 13 cases in which the molecular studies contributed to the interpretation of the cytogenetic findings, the two results did not agree with respect to the meiotic stage of nondisjunction. A relatively high frequency of crossing-over on either the short arm or proximal long arm of chromosome 21 could explain these results and may be a mechanism leading to nondisjunction.

Chromosome Aberrations↗
PubMed1992

[Pathophysiologic and anesthesiologic characteristics of patients with leukemia].

Leukaemia and its associated therapy result in pathophysiological peculiarities relevant to anaesthesia. Leukaemic patients suffer from anaemia, coagulation disorders, and the consequences of immunosuppression. In addition, some patients show infiltrations of the oropharynx, potentially resulting in difficult intubation and/or pharyngeal haemorrhage. Mediastinal masses can induce complete airway obstruction during general anaesthesia. Patients with a white blood cell count (WBC) greater than 100,000/mm3 (hyperleukocytosis) can suffer from the leukostasis syndrome with acute respiratory failure as well as cerebral vascular occlusions and bleeding due to increased blood viscosity and disturbed microvascular perfusion. Since this syndrome may be triggered by surgery, the WBC should be reduced prior to general anaesthesia in patients with hyperleukocytosis. To avoid development of the leukostasis syndrome, transfusion of packed red cells should be restricted in these patients. Hyperleukocytosis can simulate in-vitro hypoxaemia due to the excessive oxygen consumption of the mass of leukaemic blood cells during routine blood gas analysis. Therapy of leukaemia can lead to the tumor-lysis syndrome with hyperuricaemia, hyperphosphataemia, hyperkalaemia, hypocalcaemia, and hypoglycaemia, and may induce acute renal failure. Since drug interactions have only been evaluated for the combination of two or three drugs, interactions of cytotoxic agents with anaesthetics can hardly be predicted because of the large number of drugs simultaneously administered to leukaemic patients. The heart and lungs are target organs for the acute or chronic side effects of cytotoxic drugs, resulting in non-cardiogenic pulmonary oedema (e.g., cytosine-arabinoside), lung fibrosis (e.g., bleomycin), or arrhythmias and cardiac failure (e.g., adriamycin). The severity of these side effects depends on pre-existing organ disease and only in part on drug dosage. Only HLA- and CMV-compatible blood components should be administered to leukaemic patients. Hyperleukocytosis and the first days of cytotoxic treatment represent relative contraindications to general anaesthesia.

Airway Obstruction↗