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D Ritter

Publications and source records attributed to D Ritter.

At least 55 records · Page 3Linked to original sources
PubMed1992

Localization, synthetic regulation, and biology of renal atriopeptin-like prohormone.

We recently demonstrated the synthesis and secretion of an atriopeptin (AP)-like prohormone in rat neonatal and adult cortical kidney cell cultures. However, these cultures contained proximal as well as distal tubular epithelial cells; thus characterization of the peptide synthetic cell was not possible. Also, by immunohistochemical techniques, we localized this AP-like prohormone to the distal cortical nephron in adult rat kidney. In this study, we examined further details of the kidney cortical cell type that expresses and secretes this AP-like peptide in adult renal cortical cell cultures, its regulation by adenylate cyclase via adenosine 3',5'-cyclic monophosphate (cAMP) generation, and its ability to stimulate guanylate cyclase. Tubular fragments were derived from cortical tissue of adult Sprague-Dawley rats and separated into four fractions on Percoll density gradient. Cell cultures generated from fraction 3 secreted 5- to 10-fold the amount of this renal peptide compared with fractions 2 and 4. Further cell culture characterization was performed by agonist-stimulated cAMP formation, kallikrein localization, and prostaglandin E2 formation. From these analyses, it was determined that tissue band 3 was enriched for distal cortical connecting tubules. To further evaluate whether mammalian distal nephron synthesizes an AP-like protein, we determined that two immortalized mouse cell lines, derived from either the distal convoluted tubule or cortical collecting tubule, synthesized a radiolabeled AP after being pulsed with [35S]-methionine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Renal expression of the gene for atrial natriuretic factor.

To date, atrial natriuretic factor (ANF) mRNA has eluded detection in the mammalian kidney, although we and others have identified ANF protein in the kidney using immunohistochemical and immunoassay techniques. Furthermore, we have demonstrated the synthesis and secretion of the ANF prohormone in the distal cortical nephron of the intact rat kidney and from rat primary cultured renal distal cortical tubular epithelial cells. In the present study, we show that the ANF gene is expressed in the kidney. Amplification of RNA isolated from rat distal cortical tubular epithelial cultures using ANF specific primers produced a 213-bp fragment that specifically hybridized to a 32P-labeled ANF cDNA. We had previously demonstrated these cultures to be enriched for the renal ANF synthetic and secretory cell type. However, we were unable to detect an ANF gene transcript in total rat kidney RNA using the above-mentioned polymerase chain reaction (PCR) conditions. Reanalysis of normal rat kidney PCR products by a second round of PCR amplification using nested primers successfully identified ANF mRNA. Similar to cultured kidney epithelial cells, normal rat kidney expresses ANF mRNA, but at a very low abundance, thus necessitating two rounds of PCR amplification. Further characterization of rat cortical distal tubular epithelia poly(A)+ RNA by Northern analysis revealed two ANF gene transcripts. A 1.0-kb message that comigrated with rat atrial ANF mRNA, and a second larger 1.4-kb transcript. These studies further substantiate the synthesis of ANF in the mammalian kidney. Unlike the mammalian heart, the kidney contains two ANF gene transcripts.

Animals↗
PubMed1991

Synthesis and secretion of an atriopeptin-like protein in rat kidney cell culture.

The synthesis and secretion of an atriopeptin(AP)-like prohormone (AP126ir) has been demonstrated in rat neonatal renal cell cultures. AP126ir could be detected in the cellular extract and the medium from cultured kidney cells of neonatal and adult rats using an enzyme immunoassay specific for cardiac AP prohormone. On reverse-phase high-performance liquid chromatography, the AP obtained from the extract and the medium comigrated with cardiac AP prohormone. Incubation of the renal AP in the medium with thrombin resulted in the generation of a single low molecular mass peak which migrated with the cardiac carboxy-terminal 28-amino acid AP. Neonatal kidney cells pulsed with [35S]methionine secreted radiolabeled AP126ir, which was detected by immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis chromatography. Incubation of neonatal kidney cell cultures with the protein synthesis inhibitor cycloheximide resulted in a significant decrease in both the cellular and media AP. No decrease in cellular and media AP was detected when neonatal atrial cultures were treated with cycloheximide. These data demonstrate the de novo synthesis of an AP prohormone-like protein in neonatal rat kidney cultures. Furthermore, unlike the atria, kidney cells appear to secrete AP solely by constitutive means. In primary adult rat kidney cultures, most of AP126ir was detected in the cortical tubule fraction demonstrating that these cells secrete AP126ir in the adult rat kidney. We hypothesize that the renal AP may be important as an autocrine or paracrine regulator of renal function.

Animals↗
PubMed1990

Comparison of enzyme immunoassay with radioimmunoassay for the detection of antibody to hepatitis B core antigen as the only marker of hepatitis B infection in a population with a high prevalence of hepatitis B.

Enzyme immunoassay (EIA) and radioimmunoassay (RIA) for the detection of antibody to hepatitis B core antigen (anti-HBc) were compared using serum specimens from Alaska Natives screened during a hepatitis B control program that were initially positive by EIA for only anti-HBc. Of 36 specimens from persons previously HBsAg positive but who were now only anti-HBc positive by EIA, 94.4% were anti-HBc positive by both assays, with anti-HBc levels exceeding 93% inhibition. Low-level antibody to hepatitis B surface antigen (anti-HBs) (less than 10 SRU) and antibody to hepatitis Be (anti-HBe) were also present in 50% and 48% of specimens positive for anti-HBc, respectively. Of 148 specimens from persons initially positive for only anti-HBc by EIA who had no previous documentation of any hepatitis B virus (HBV) infection, 64.5% were positive by repeat testing for anti-HBc by both assays, and anti-HBc levels in this sample exceeded 70% in 91.6% and 80.2% of specimens by EIA and RIA, respectively. Low-level anti-HBs and anti-HBe were present in 45.8% and 15.6%, respectively. EIA detection of anti-HBc was found to be less specific than RIA. Of specimens positive for anti-HBc by EIA, 14.8% were negative by RIA. The specificity of the EIA could be improved with respect to RIA by increasing the cut-off from 48% to 68%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Prognostic factors in patients dying of well-differentiated thyroid cancer.

While some well-differentiated cancers of the thyroid gland are unusually aggressive, most have a more benign clinical behavior, making it difficult to evaluate factors possibly influencing patient survival such as initial surgical treatment. By studying 135 patients who received their initial surgical therapy at our institution, we have defined the prognostically significant factors. Sixteen patients (11.9%) died of disease during a ten- to 20-year follow-up period. Significant factors associated with death from disease were aged 40 years or older, primary lesion size of 2.5 cm or greater, presence of invasive characteristics, and presence of distant metastases. We recommend total thyroidectomy and postoperative sodium iodide I 131 therapy in patients 40 years of age or older, while suggesting a less aggressive approach may be appropriate in the younger patients.

Actuarial Analysis↗
PubMed1989

Chest pain evaluation unit: a cost-effective approach for ruling out acute myocardial infarction.

We compared a "cardiac profile" test with standard creatine kinase (CK) and lactic dehydrogenase (LD) electrophoresis in 798 cases of possible acute myocardial infarction (MI). The cardiac profile enzyme screen (CK-B, CK, LD) used on 495 patients who came to the emergency department with chest pain suggestive of acute MI but without diagnostic ECG changes. Instead of admission to the coronary care unit, they were placed on observation status (Chest Pain Evaluation Unit) for a period up to 20 hours (average 11.1 hours). Using the results of the cardiac profile, 327 were able to be sent home. Of the 168 patients admitted, only 30 (18%) had subsequent enzyme evidence of myocardial necrosis. Use of the chest pain evaluation unit resulted in an 80% reduction in cost of ruling out acute MI for the 327 patients not admitted.

Adult↗
PubMed1987

A comprehensive programme to reduce the incidence of hepatitis B virus infection and its sequelae in Alaskan natives.

In 1983, a comprehensive programme was introduced to halt the spread of hepatitis B virus (HBV) infection and to reduce mortality from hepatocellular carcinoma (HCC) in Alaskan Natives, in whom the incidence of HBV infection was high. This programme includes: serological screening of all Alaskan Natives; immunisation of susceptible persons, including all newborn babies, with hepatitis B vaccine; and testing HBsAg-positive carriers twice a year for alpha-fetoprotein (AFP) to detect HCC at an early stage. By October, 1986, over 53,000 Alaskan Natives (84% of the total Native population) had been tested for HBV serological markers and 80% of the identified susceptibles had been or were being vaccinated against HBV. After complete immunisation of 90% of the susceptibles in the area with the highest infection rates in Alaska, the annual incidence of acute symptomatic HBV infection decreased from 215 to 14 cases per 100,000 population. After the introduction of AFP screening, the 1-year-case-fatality rate for HCC fell, from 100%, to 50%.

Alaska↗
PubMed1987

Baseline and stimulated ANF plasma levels: is an impaired stimulus-response coupling diagnostically meaningful?

Plasma levels of ANF were determined and chromatographically analysed in normotensive controls, cirrhotic patients with and without ascites, hypertensive patients, patients with congestive heart failure and heart transplant recipients. A comparison of baseline plasma levels allowed for the conclusion that cirrhotic patients do not differ in this regard from control subjects (9.0 +/- 1.3, n = 41 vs. 9.6 +/- 1,0 fmol/ml, n = 51). Cirrhotic patients with ascites do not have lower plasma levels than cirrhotic patients without ascites (8.8 +/- 1.4, n = 8 vs 8.6 +/- 1.5 fmol/ml, n = 10). Stimulation of the ANF-system by head-out water immersion, however, revealed an impaired increase in ANF release in cirrhotic patients with ascites (146 +/- 18% vs 204 +/- 16%). Patients with cardiovascular disease display tonically-elevated ANF plasma levels. Heart failure patients displayed the highest plasma concentration (81.5 +/- 32.7 fmol/ml, n = 17), whereas plasma levels in hypertensive patients ranged from normal to greatly elevated (61.7 +/- 13.2 fmol/ml, n = 36). Heart transplant recipients also had significantly elevated plasma levels as compared to control subjects (31.2 +/- 7.9 fmol/ml, n = 14) but levels were lower than in hypertensive patients in spite of a comparable arterial pressure. Short term ventricular pacing (f = 150/min for 5 min) revealed an impaired phasic activity of the ANF system in heart failure patients and heart transplant recipients.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Natriuretic Factor↗
PubMed1986

Atrial natriuretic factor in plasma of patients with arterial hypertension, heart failure or cirrhosis of the liver.

Since the discovery of the atrial natriuretic factor (ANF) an endocrine function has been attributed to the mammalian heart. This function may include definition of optimal conditions for efficient performance of the heart, e.g. by reduction of afterload in hypertension or of preload and afterload in heart failure. Plasma ANF levels were measured in various cardiovascular disease states and compared with those of controls and of patients with liver cirrhosis. Plasma ANF levels in hypertensive patients were sevenfold higher than in controls, and in patients with heart failure 40-fold higher than normal values. Small differences were detected between controls and patients with cirrhosis of the liver, in spite of the impaired renal sodium handling seen in cirrhotics. Plasma ANF levels were significantly correlated with haemodynamic parameters and were inversely related to the cardiac index. Treatment with an angiotensin converting enzyme inhibitor led to a significant decrease in plasma ANF levels in parallel with the haemodynamic improvement. Preliminary chromatographic analysis suggested differences in the structure of plasma ANF between normotensive and hypertensive subjects.

Atrial Natriuretic Factor↗
PubMed1986

Molecular weight heterogeneity of plasma-ANF in cardiovascular disease.

Structural differences of circulating ANF may partly explain why the physiological response of the heart in controlling volume/pressure loading in cardiovascular disease states remains insufficient in spite of elevated ANF plasma levels. Structural analysis of plasma ANF immunoreactivity was performed by means of gel permeation of plasma extracts subsequent to radioimmunoassay. ANF plasma levels in hypertensive patients or patients with congestive heart failure (CHF) were significantly elevated as compared to normotensive controls or cirrhotics. (61.7 +/- 13.2 or 81.5 +/- 32.7 versus 9.6 +/- 1.0 or 10.3 +/- 1.3 fmol/ml, p less than 0.01). In CHF patients, ANF plasma concentrations were significantly correlated to right atrial and pulmonary capillary wedge pressures. ANF release was stimulated by head-out water immersion both in normotensive controls and cirrhotic patients. No higher molecular weight forms were detected in plasma of control subjects. 15,000-dalton ANF, in addition to 3080-dalton ANF, was present in plasma of hypertensive patients and, in trace amounts, of cirrhotic patients. In some CHF patients, elevated ANF plasma levels predominantly comprised higher molecular weight forms of approx. 15,000 daltons MW, in addition to considerable amounts of ANF immunoreactivity presumably bound to larger proteins that eluted in the void volume. The data suggest that a dysregulation of post-translational processing of ANF may contribute to the pathophysiology of cardiovascular disease.

Atrial Natriuretic Factor↗
PubMed1984

A preliminary review of the Müller acetabular and Burch-Schneider antiprotrusio support rings.

A high incidence of acetabular loosening following total hip arthroplasty is emerging as long term follow-up studies become available. The Müller and Burch-Schneider acetabular supports are indicated for acetabular deficiencies which are frequently present during revision hip arthroplasty. The Burch-Schneider support is indicated where the deficiencies are of such magnitude that the Müller ring does not have stable seating prior to screw fixation. These devices bring the resultant of forces across the hip joint under the acetabular roof and provide metal backing for the acetabular cup. They have the additional advantage of screw fixation which in the Müller ring is in line with the resultant of forces across the hip joint. In a one to three year follow-up of twenty-five hip replacements in twenty-four patients, the Müller support ring was used in twenty hips and the Burch-Schneider in five hips. The results were satisfactory and indicate that these supports are valuable in the treatment of patients with acetabular deficiencies.

Acetabulum↗
PubMed1982

A comprehensive rabies control program in Alaska.

In 1975 the State of Alaska initiated a comprehensive Rabies Control Program. Lay vaccinators trained and certified by the state provided animal vaccination in rural areas. From 1975 through 1980, 182 persons received post-exposure rabies prophylaxis with Human Rabies Immune Globulin (HRIG) plus Duck Embryo Vaccine (DEV), or Human Diploid Cell Vaccine (HDCV), while 2,569 persons initially thought to have been exposed were not treated after consultation, at a cost saving of approximately $3,220,241.

Alaska↗
PubMed1980

Nasopharyngeal carcinoma in Alaskan Eskimos Indians, and Aleuts: a review of cases and study of Epstein-Barr virus, HLA, and environmental risk factors.

The records of thirty-one patients with nasopharyngeal carcinoma (NPC) diagnosed from 1966 through 1976 among the Alaskan native population (Eskimo, Aleut, Indian) were reviewed. There were 25 males and six females, which results in relatively high incidence rates per 100,000 of 13.5 for males and 3.7 for females. Clinical and pathologic features were similar to those found among southern Chinese NPC patients. Five-year survival rate was 48%. Antibodies to Epstein-Barr virus were higher in NPC patients than in patients with other tumors or matched controls. On histocompatibility testing Sin-2 was not detected, nor was there significantly increased frequency of A2. Instead, BW40 and a second locus blank occurred more often among NPC patients than among other groups. In response to a questionnaire, NPC patients more often reported use of salt fish in the childhood diet, smoking of cigarettes, and exposure to noxious inhalants than did controls, but the differences were not statistically significant.

Adult↗