Biomedical subjects
M D Penney
Publications and source records attributed to M D Penney.
Reduced renal hemodynamic response to atrial natriuretic peptide in elderly volunteers.
Aging is associated with decreased ability to excrete salt and water, thus increasing the susceptibility to volume overload in older individuals. Meanwhile, plasma levels of atrial natriuretic peptide (ANP) increase progressively with age for unknown reasons. We compared the natriuretic and renal hemodynamic responses to low-dose ANP infusion in an elderly group of volunteers (mean age, 74 years) with those of a group of younger subjects (mean age, 29 years). A significant reduction below baseline values in effective renal plasma flow occurred in the young group after the 2-hour peptide infusion (657 +/- 125 v 476 +/- 92 mL/min [mean +/- 1 SD]) when compared with the elderly group (two-way analysis of variance; P < 0.02). A concomitant increase in renal vascular resistance was noted in the young group only during the same period (6,631 +/- 1,384 v 9,136 +/- 2,126 dyn s cm2 x 10(6)). This increase was also significantly higher than that in the elderly group (analysis of variance; P < 0.02). Both groups demonstrated similar natriuretic responses. Absolute sodium excretion had increased significantly above baseline values in both young and elderly subjects at the end of the 2-hour peptide infusion (111 +/- 25 mumol/min to 183 +/- 33 mumol/min v 107 +/- 23 mumol/min to 198 +/- 56 mumol/min) and remained elevated until 1 hour postinfusion. We conclude that the elderly subjects in our study demonstrated a diminished renal hemodynamic response to infusion of ANP while preserving a natriuretic response similar to that found in the younger subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
The frusemide test: simple screening test for renal acidification defect in urolithiasis.
Urinary pH was first labelled as a risk factor for patients with recurrent calcium stone disease of the renal tract in 1978. The standard diagnostic test for patients with a history of stones, who appear to have urinary acidification defects is the ammonium chloride test. However, the performance of this test results in significant morbidity, particularly nausea and vomiting, and as a result there is little enthusiasm for screening for such defects. We describe a screening test that may be used to determine which patients require more definitive testing. It involves an oral dose of frusemide (40 mg) followed by half-hourly urine sampling for pH. For the detection of a renal tubular acidification defect, the frusemide test had sensitivity = 100%, specificity = 82%, predictive value of a positive result = 40%, predictive value of a negative result = 100%, screening efficiency = 84%, and there was no morbidity. During the ammonium chloride test 80% of the patients vomited or felt very nauseated.
Serum screening for Down's syndrome.
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Early diagnosis of ectopic arginine vasopressin secretion.
We describe a patient who presented with the syndrome of inappropriate antidiuretic hormone secretion (SIADH) 2 months before clinical evidence of bronchogenic malignancy. Because of the potential for the ectopic production of atrial natriuretic peptide (ANP) to mimic SIADH, both hormones were measured in this hyponatremic patient to seek a possible marker of tumor activity. A hypertonic saline infusion at presentation revealed excessive osmotically decoupled secretion of arginine vasopressin but a normal ANP response.
Serum L-arginine in hypercholesterolaemia.
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Volume of normal prostate, of prostate cancer, and of benign prostatic hyperplasia: are correlations with prostate specific antigen clinically useful?
This retrospective study correlated prostate volume, determined by transrectal ultrasonography, with serum prostate specific antigen (PSA), by Deming regression analysis, in patients with confirmed benign prostatic hyperplasia (BPH) and patients with non-metastatic (M0) or metastatic (M1) prostate cancer. In BPH, a highly significant correlation was found between log10[PSA] and prostate volume. When this PSA/volume regression pattern for BPH was used as a reference standard, all 17 patients with M1 prostate cancer and 83% of the 23 patients with M0 disease were discriminated from BPH.
Ultrasonographic dating of pregnancy causes significant errors in Down syndrome risk assessment that may be minimized by use of biparietal diameter-based means.
OBJECTIVES: Gestational dates assessed by ultrasonographic measurement of fetal dimensions are usually quoted in terms of complete weeks because the uncertainty of ultrasonographic measurement is approximately +/- 7 days. This study examines the effect of ultrasonographic dating on Down syndrome risk assessment. STUDY DESIGN: The effect of small changes in measured biparietal diameter resulting in a change in estimated gestational week and the benefits of a more precise measure of fetal gestational age (raw biparietal diameter) are examined mathematically. RESULTS: If maternal serum alpha-fetoprotein and human chorionic gonadotropin are used to assess Down syndrome risk, risks assessed with ultrasonographically determined dates may be less than or equal to 45% too high for fetuses with biparietal diameter at the lowest end of the size band and less than or equal to 22% too low with biparietal diameter at the top of the size band. If the results for maternal serum alpha-fetoprotein, human chorionic gonadotropin, and unconjugated estriol are used, these figures become less than or equal to 150% and less than or equal to 60%, respectively. CONCLUSION: If ultrasonography is used to assess gestational age, the raw biparietal diameter and not the estimated week of gestation must be used to derive means for calculation of multiples of the mean.
Inter-relation between measurement of serum prostatic specific antigen and transrectal ultrasound in the diagnosis of benign prostatic hyperplasia and prostatic cancer.
Serum prostatic specific antigen (PSA) and ultrasound-determined prostatic volume (UPV) were measured in 50 patients with histologically proven benign prostatic hyperplasia (BPH) and in 40 patients with histologically proven prostatic cancer of whom 17 had evidence of distant metastases (M1) and 23 did not (M0). A good correlation between log PSA and UPV was demonstrated in the BPH group and rearrangement of the linear regression equation allowed calculation of a single variable--the log PSA corrected to a standard prostate volume for any given individual. A volume-corrected PSA correctly identified all patients with M1 disease and greatly improved but did not eliminate overlap of M0 disease with BPH. Reduction of serum PSA to a single volume-corrected variable will allow the introduction of practical and optimum protocols for the management of patients with prostatic enlargement.
Renal sodium retention does not occur during the luteal phase of the menstrual cycle in normal women.
OBJECTIVE: To determine whether weight gain due to renal sodium and water retention occurs in the luteal phase of the normal menstrual cycle. DESIGN: Prospective observational study. SETTING: Research laboratory installed with modified spa bath. SUBJECTS: Ten normal healthy women. INTERVENTION: Each subject underwent two experiments, one in each phase of the menstrual cycle, involving 3 h head-out water immersion and a pre- and post immersion control hour. 25 ml blood samples were obtained every hour before, during and after water immersion. MAIN OUTCOME MEASURES: Renal and hormonal responses to water immersion during the luteal and proliferative phases of the cycle. RESULTS: There was no change in weight, creatinine clearance, basal sodium excretion or plasma atrial natriuretic peptide between the two phases of the cycle. There was a significant rise in basal progesterone, plasma aldosterone and plasma renin activity in the luteal phase of the ovulatory cycles. Renal and hormonal responses to immersion including sodium and calcium excretion, elevation of atrial natriuretic peptide (ANP) and suppression of plasma aldosterone and plasma renin activity were identical in the two phases of the menstrual cycle. CONCLUSION: We found no evidence to support the hypothesis that renal sodium and water retention occurs in the luteal phase of the normal menstrual cycle.
Creatine kinase isoforms: investigation of inhibitors of in vitro degradation and establishment of a reference range.
The in vitro stability of creatine kinase isoforms was examined by separation with high voltage electrophoresis. The effect of inhibitors of carboxypeptidase was evaluated. Preservation of samples is essential to inhibit in vitro changes in isoform pattern. EDTA at a final concentration of 15 mmol/L is recommended. Using appropriately preserved samples, normal reference intervals for the MM isoforms have been established.
Radioimmunoassays of arginine vasopressin and atrial natriuretic peptide: application of a common protocol for plasma extraction using Sep-Pak C18 cartridges.
A rapid vacuum-driven procedure, using pre-treated Sep-Pak C18 cartridges, has been developed for the simultaneous extraction of arginine vasopressin (AVP) and atrial natriuretic peptide (ANP) from plasma. Non-specific interference was removed by fractional elution with an aqueous methanol/trifluoroacetic acid (TFA) mixture. AVP and ANP were coeluted under positive pressure with a methanol/TFA mixture and the eluates air-dried before measurement using separate radioimmunoassays. Assay ranges for AVP and ANP were 0.12-29.5 pmol/L and 0.65-162 pmol/L, respectively, with mean recoveries (standard deviation in parentheses) for AVP of 96.4% (5.5%) at a level of 11.8 pmol/L and for ANP of 94.8% (5.9%) at a level of 32.4 pmol/L. The extraction and assay procedures were validated by observing the changes in plasma AVP and ANP concentrations in normal subjects at different stages of hydration and in elderly patients during treatment for congestive cardiac failure.
Can serum prostate-specific antigen replace bone scintigraphy in the follow-up of metastatic prostatic cancer?
Bone scintigraphy is the most sensitive imaging technique for the initial detection of bone metastases and is widely used in the staging of prostatic cancer. This study was performed to assess whether the development of further bone metastases can be detected by serial measurements of the serum glycoprotein prostate-specific antigen (PSA) as an alternative to follow-up scintigraphy. The bone scintigrams and PSA levels of 101 patients with metastatic prostate cancer entered into two therapeutic trials have been reviewed. Serial results of both investigations were available in 59 cases. In three cases new bone deposits were observed without a corresponding rise in PSA. In two other cases the scintigrams were considered to be suspicious of progression with no change in PSA levels; however, further follow-up indicated that these changes were not due to metastases. In 13 cases PSA levels were rising in advance of new deposits on the scintigrams. In the remaining 41 cases the PSA levels and scintigraphic findings paralleled each other. We conclude that serial estimation of PSA levels is a simpler marker for disease progression than bone scintigraphy in metastatic prostatic cancer, but that neither technique in isolation gives complete accuracy.
Estimations of gestational age and screening for Down's syndrome.
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Prenatal prediction of Down syndrome.
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Changes in AVP following aggressive diuretic therapy of severe congestive cardiac failure in elderly patients.
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The effect of weight correction on risk calculations for Down's syndrome screening.
Recent advances in prenatal screening have led to the possibility that the risk of Down's syndrome associated pregnancy may be assessed by blood tests for maternal serum alphafetoprotein, human chorionic gonadotrophin (and possibly unconjugated oestriol) taken at 15-18 weeks of gestation. In neural tube defect screening correction of maternal serum alphafetoprotein for maternal weight has been recommended, although the precise method for weight correction is still under debate. We report an assessment of weight correction for maternal serum alphafetoprotein and human chorionic gonadotrophin based on 1408 singleton pregnancies and for unconjugated oestriol based on 197 singleton pregnancies. We demonstrate that weight correction of maternal serum alphafetoprotein and human chorionic gonadotrophin is statistically valid but that correction of unconjugated oestriol is not.
The effect of lithium therapy on arginine vasopressin secretion and thirst in man.
Lithium therapy is known to reduce the renal responsiveness to arginine vasopressin (AVP: the antidiuretic hormone in man) and a proportion of treated patients develop polyuria and polydipsia. In this study seven nonpolyuric female patients receiving lithium treatment for an affective disorder (lithium group) were age-matched with seven healthy females (control group). The mean response of plasma AVP to osmotic stimulation was significantly enhanced in the lithium group but the mean osmotic threshold for AVP release was unchanged. Thirst appreciation in the lithium group commenced and increased overall at an osmotic stimulus 5 mmol/kg less than the control group. It is suggested that primary thirst does play a role in the expression of lithium-induced polyuria.