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Biomedical subjects

W J Stone

Publications and source records attributed to W J Stone.

At least 109 records · Page 6Linked to original sources
PubMed1970

Sickle-cell trait.

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Anemia, Sickle Cell↗
PubMed1967

Renal metabolism of alanine.

In the acidotic dog, alanine is extracted from plasma and utilized as a precursor of ammonia. Simultaneously, it is formed de novo within tubular cells and added to renal venous blood. When plasma concentration is within a normal range, production of alanine greatly exceeds utilization. Increasing the plasma concentration reduces production and increases utilization of plasma alanine. The infusion of glutamine increases the renal production of alanine without appreciable change in utilization of plasma alanine. These results are consonant with the view that alanine is metabolized by transamination with alpha-ketoglutarate to form glutamate, which is subsequently deaminated oxidatively to liberate ammonia. Conversely, alanine is formed by transamination of pyruvate with either glutamate or glutamine and is added to renal venous blood. The balance between production and utilization is dependent, at least in part, on the concentrations of the reactants.

Alanine↗
PubMed1967

Pathways of ammonia metabolism in the intact functioning kidney of the dog.

Studies in which (15)N-labeled precursors of urinary ammonia were infused into the artery of an intact functioning kidney of an acidotic dog have led to the following conclusions: Preformed ammonia and ammonia derived from the amide nitrogen of plasma glutamine are added directly to urine without significant incorporation into amino acid intermediates of renal tissue. Thus, reductive amination of alpha-ketoglutarate to form glutamate does not occur to an appreciable extent nor is there significant transfer of the amide nitrogen of glutamine to the corresponding keto acids to form glutamate, aspartate, alanine, or glycine. The enzyme system "glutaminase II" may participate to a significant extent in the metabolism of glutamine by forming aspartate and alanine by direct transamination of oxalacetate and pyruvate and liberating the amide nitrogen as ammonia. Renal alanine exists as a well mixed pool derived in roughly equal amounts from filtered and reabsorbed plasma alanine and newly synthesized alanine. The alanine pool of tubular cells does not equilibrate with the alanine of peritubular capillary blood. Transfer of the nitrogen of alanine to alpha-ketoglutarate and subsequent oxidative demination of the resulting glutamate can account for the ammonia formed from alanine. Glycine is not an important intermediate in renal nitrogen metabolism.

Acidosis↗
PubMed1967

Diffusion equilibrium for ammonia in the kidney of the acidotic dog.

Inflow of preformed ammonia in arterial blood, renal production of ammonia, outflow of ammonia in renal venous blood, and urinary excretion of ammonia were measured during the infusion of (15)NH(4)Cl into one renal artery of dogs with chronic metabolic acidosis. Our results show that the specific activity of ammonia measured in the urine and that calculated in the renal pool agree within 95%. Pool specific activity is obtained by dividing the rate of infusion of isotope by the pool turnover rate, i.e., the sum of the rate of ammonia output in the urine and that in renal venous blood. An average of 35% of urinary ammonia is derived from arterial ammonia in these experiments. We conclude that ammonia is distributed evenly throughout all phases of the kidney within a period less than the transit time of blood through the kidney. Furthermore, from the proportion of urinary ammonia we found to be derived from preformed arterial ammonia (35%), and from our previous demonstration that 73% of urinary ammonia derives from deamidation and/or deamination of plasma glutamine, alanine, glycine, and glutamate, we can account for all of the ammonia that leaves the kidney in renal venous blood and in urine.

Acidosis↗
PubMedDate not supplied

Long-term bumetanide treatment of patients with edema due to renal disease. Cooperative studies.

Bumetanide was compared with furosemide in a total of 43 outpatients with edema due to renal disease, selected from three clinics following a uniform protocol. By random selection, 31 patients received 1 to 10 mg/day bumetanide, and 12 received 40 to 400 mg/day furosemide for at least six months. The patients were evaluated clinically, by standard laboratory tests, as well as by ECG, audiometry, eye examination, and mammary examination. Pooled statistical analysis of the results was done. Edema, body weight, and abdominal girth were reduced during both treatments. There was no significant difference in the mean response to the two diuretic agents by the two sided probability test in the other parameters studied, e.g., supine and standing blood pressure and pulse, serum electrolytes (sodium, potassium, chloride), and uric acid. There were no differences in liver function tests, hematology, or chest x-ray, and no remarkable effects on hearing. Gynecomastia improved in some patients while being treated with bumetanide after spironolactone was discontinued. Adverse reactions in patients on bumetanide which were considered possibly or probably related to the drug were muscle cramps (two patients); and vertigo, headache, muscle pain, urticaria, chest pain, arthritis, dehydration, postural hypotension, and leg cramps (one each). Laboratory abnormalities in both groups were generally those that could be attributed to the pharmacologic action of the diuretics or due to the patients' underlying disease states. No drug-related adverse effects were noted in ECG, ophthalmologic examinations, or chest x-rays. Two patients in the furosemide group had a probably or possibly drug-related loss of hearing sensitivity. In summary, bumetanide appeared to be as safe and as efficacious as furosemide in controlling edema and hypertension in patients with renal disease.

Bumetanide↗
PubMedDate not supplied

Adverse antibiotic effects associated with renal insufficiency.

We review the English-language literature on antibiotic-associated adverse reactions in patients with renal insufficiency in order to highlight this important but often overlooked clinical problem. Because many adverse reactions to antibiotics are not dependent on renal function, we have attempted to review only those reactions that are believed to be associated with renal insufficiency or that have been reported in patients with impaired renal function. Adverse effects of antibiotics in this setting can be divided into six major categories: neurologic toxicity, coagulopathy, nephrotoxicity, hypoglycemia, hematologic toxicity, and aminoglycoside inactivation by penicillins. Neurologic toxicity can be further divided into central nervous system toxicity consisting primarily of encephalopathy and seizures, ototoxicity, peripheral neuropathy, and neuromuscular blockade/respiratory depression. We explore the factors in uremia that may contribute to the susceptibility of patients with renal insufficiency to the adverse effects of antibiotics. Moreover, we make general recommendations regarding the use of the discussed antibiotics in patients with compromised renal function.

Acute Kidney Injury↗
PubMedDate not supplied

Primary renal candidiasis with renal granulomata and salt-losing nephropathy.

A patient is reported whose illness was characterized by chronic renal failure associated with persistent salt-wasting, chronic nephrolithiasis, and candiduria which was documented to be arising from the upper urinary tract. Intravenous amphotericin B was effective in eradicating candiduria. However, bilateral nephrectomy was ultimately performed which revealed extensive involvement of the renal parenchyma with classic caseating granulomas apparently related to renal candidiasis. Severe medullary erosion and tissue loss existed which appeared to result in disproportionate medullary destruction which was probably the most significant factor in explaining the patient's salt-losing state. The patient has since been satisfactorily managed with maintenance hemodialysis.

Body Weight↗
PubMedDate not supplied

Clinical trials of a cryoglobulin filter.

The authors report the results of clinical trials of a high capacity cryoglobulin filter (Cryofilter) in seven patients with cryoglobulinemia unresponsive to high doses of prednisone or immunosuppressive drugs who required plasmapheresis. The objective of this study was to test the safety and efficacy of the cryofilter in a limited patient population according to the investigational Device Exemption guidelines of the FDA. The cryoglobulins were selectively filtered from plasma at 4 degrees C by a cryofilter characterized by a membrane surface area of 0.135 m2 and an average pore size of 4.3 microns. Safety was evaluated by patients vital signs, complement activation, and clinical score of symptoms in the course of 10 treatments. Efficacy of cryofiltration was evaluated by comparing sieving of the cryoglobulins to that of albumin; immunoglobulins G, A, and M; and fibrinogen. All seven patients completed the series of 10 treatments without notable complement activation or any signs of discomfort. The cryofilter was particularly selective in patients with high cryoglobulin concentrations. Improvement in clinical symptoms was observed in all patients.

Adult↗
PubMedDate not supplied

Cryofiltration apheresis for treatment of cryoglobulinemia associated with hepatitis C.

Cryofiltration apheresis (CA) is a specific therapy for treatment of patients with cryoglobulinemia. We evaluated the safety and efficacy of CA in patients with mixed cryoglobulinemia associated with hepatitis C. As reported previously, the Cryoglobulin Filter comprises a membrane module inside a refrigeration unit on-line with a Spectra Apheresis System (COBE, Denver, CO). The efficacy of cryofiltration was measured by comparing the sieving coefficient of cryoprecipitable proteins (CPP) to that of albumin and comparing the systemic CPP concentration ratio post to pre treatment. Five patients were enrolled in this study, and a minimum of 10 procedures were performed for each patient. The risk for hepatitis C was multiple blood transfusions, intravenous drug abuse, immunosuppressive therapy, or renal transplantation. Four patients had Type II mixed cryoglobulinemia, and one patient had Type III. Four patients had chronic renal failure; one with liver cirrhosis received alpha interferon along with CA. One patient had no response to conventional plasma exchange and immunosuppressive therapy secondary to repeated infections and sepsis; CA was the only viable therapy for this patient. The maximum CPP concentration before therapy ranged from 1,440 to 7,440 micrograms/ml. The plasma CPP sieving coefficient at 1 L filtrate ranged from 0.25 to 0.74 (average +/- SE, 0.51 +/- 0.19; n = 39). The sieving coefficient for albumin was 1 (n = 50). The systemic CPP ratio post to pre treatment ranged from 0.28 to 0.83 (average +/- SE, 0.59 +/- 0.20; n = 37). No adverse effects specific to CA were observed. The CA was safe and effective and possibly the only choice of therapy in patients with cryoglobulinemic hepatitis C who have no response to plasma exchange and immunosuppressive therapy.

Adult↗
PubMedDate not supplied

Radionuclide measurement of differential glomerular filtration rate.

The authors sought to determine whether radionuclides could provide a reasonable estimate of differential renal function in five normal dogs and six dogs with unilateral segmental renal infarction. Glomerular filtration rate (GFR) of each kidney was measured by the standard technique using constant infusions of 99mTc-DTPA, iothalamate, and creatinine following ureteral catheterization. These results were correlated with total GFR estimated by bolus injection of 99mTc-DTPA and analysis of the plasma 99mTc-DTPA disappearance curve obtained by blood sampling. Differential GFR was then calculated by multiplying the total GFR from double exponential analysis of this curve (DTPA2) by each of three measures of differential function. These include the percent differential uptake of 99mTc-DTPA and 99mTc-DMSA in the posterior projection as well as the geometric mean of 99mTc-DMSA uptake. There were good correlations between differential GFR calculated from iothalamate clearances obtained at ureteral catheterization and all noninvasive methods involving radionuclides and DTPA2 (r = 0.85 - 0.99). Single exponential analysis of the 99mTc-DTPA plasma disappearance curve was less satisfactory. The authors suggest that measurement of total and differential GFR calculated from plasma clearance of 99mTc-DTPA and external counting may be a useful method with potential clinical applications.

Animals↗
PubMedDate not supplied

Radionuclide measurement of differential glomerular filtration rate in urinary tract obstruction.

In a previous study using dogs whose renal function was rendered asymmetric by unilateral infarction, the efficacy of technetium-99m (99mTc) DTPA and DMSA in measuring differential glomerular filtration rate (GFR) was demonstrated. The present study was undertaken to determine whether the same techniques were applicable to unilateral ureteral obstruction. Five normal dogs and nine dogs with partial unilateral ureteral obstruction had determination of glomerular filtration rate by standard techniques using constant infusions of iothalamate and creatinine after ureteral catheterization. These results were compared with total GFR as measured by single injection of 99mTc DTPA and analysis of the plasma disappearance curve. Calculated differential GFR was obtained by multiplying total GFR from double exponential analysis of this curve (DTPA2) by each of three measures of differential function. These included the percent differential uptake of 99mTc DTPA and 99mTC DMSA in the posterior projection as well as the geometric mean of 99mTc DMSA uptake. There were good correlations between differential GFR determined by iothalamate clearances at ureteral catheterization and all noninvasive methods involving radionuclides and DTPA2 ( r = 0.93-0.99). Single exponential analysis of the 99mTc DTPA plasma disappearance curve was less satisfactory than double exponential analysis. These results and those reported previously support the use of radionuclides in the determination of differential GFR in a variety of clinical situations.

Animals↗
PubMedDate not supplied

Cervical bruits in hemodialysis patients.

Twenty-five patients receiving chronic hemodialysis were studied with systematic cervical auscultation and periorbital Doppler tests to determine the incidence of cervical bruits and their significance. Eighteen (72%) of the patients had bruits. All of the bruits heard in this study were loudest in the supraclavicular fossa, and in no patient was a bruit heard along the carotid arteries without a louder bruit of similar characteristics more proximally. No patient with a bruit in the area of the carotid bifurcation had an abnormal ipsilateral periorbital Doppler examination, and none had symptoms of cerebral ischemia. There was no evidence in these patients that the bruits were related to occlusive arterial disease. It is concluded that most cervical bruits in patients receiving hemodialysis are the result of a hyperdynamic circulatory state associated with anemia and arteriovenous fistulae.

Arteriosclerosis↗
PubMedDate not supplied

Perirectal and perineal infections in end-stage renal disease patients.

Eight patients with end-stage renal disease (ESRD) who developed bacterial infection of the perirectal area or perineum are reported. The diagnosis was not always straightforward. Bacteremia was seen in 3 of 8 patients and one of these died. Careful examination of the anus, rectum, and perineum should be mandatory in ESRD patients with undiagnosed fever. Treatment consisted of extensive surgical debridement and drainage along with antimicrobial therapy.

Abscess↗
PubMedDate not supplied

Stages of change, decisional balance, and self-efficacy across four health behaviors in a worksite environment.

PURPOSE: This study examined differences in decisional balance and self-efficacy scores across the five stages of change and across four health behaviors (exercise, protection from sun exposure, smoking, and dietary fat consumption), and explored the relationship between the frequency of subjects at each stage across four health behaviors. DESIGN: Data for this study were collected as part of a health behavior survey of employees. SETTING: The study was conducted in a municipal government worksite in Arizona. SUBJECTS: A total of 393 employees completed the survey. The sample was predominantly white (84.9%) and male (64.4%), with an average age of 42.2 years and a median annual household income of between $40,000 and $59,999. MEASURES: Previously validated questions to measure stages of change, decisional balance, and self-efficacy were administered, along with questions about demographic variables. RESULTS: Significant differences were found for decisional balance and self-efficacy scores across the five stages of change, but they were not significantly different between the four health behaviors. A minority of subjects (18.6%) were in the same stage of change for all four health behaviors. CONCLUSIONS: This study provides preliminary evidence that there is considerable stage specificity across multiple health behaviors. Because employees at each stage of change possess differences in terms of their pros, cons, and self-efficacy, wellness programs need to focus on stage-specific interventions.

Adult↗