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Biomedical subjects

M Menon

Publications and source records attributed to M Menon.

At least 145 records · Page 8Linked to original sources
PubMed1984

Collection and handling of 24-hour urine specimens for measurement of analytes related to renal calculi.

Analysis for calcium, magnesium, phosphorus, oxalate, uric acid, and creatinine in 24-h urine collections is often needed for the differential diagnosis of patients with renal calculi. Considerable attention has been given to improving the methods of analysis, but improper sample collection and processing can cause significant errors for calcium and oxalate in urine samples not treated with acid and for uric acid in urine samples not treated with base. The errors are related to the concentration of the analyte, the interval the sample is stored before analysis, and the original pH of the urine sample. We describe here a system of sequential acidification (to pH 1.5) and alkalinization (to pH 9) of 24-h urine samples, followed by heating at 56 degrees C for 10 min. This procedure allows accurate analysis for all the above analytes in the same 24-h collection of urine. We validated the sample-treatment protocol for 80 24-h urine collections.

Calcium↗
PubMed1983

Lack of value of radioimmunoassay for prostatic acid phosphatase as a screening test for prostatic cancer in patients with obstructive prostatic hyperplasia.

We examined the incidence of prostatic cancer in patients with an elevated radioimmunoassay for prostatic acid phosphatase and clinical benign prostatic hyperplasia on digital rectal examination. Of 295 patients screened with prostatic acid phosphatase tests 17 fulfilled the criteria of having an elevated prostatic acid phosphatase, clinically benign prostate and histological examination of the prostatectomy specimen. None of the 17 patients had histological evidence of prostatic cancer. The results confirm the predictions of mathematical models that prostatic acid phosphatase is of no practical value as a screening test for prostatic cancer in patients with clinical benign prostatic hyperplasia.

Acid Phosphatase↗
PubMed1983

Pelvic lymph node status as predictor of extracapsular tumor extension in clinical stage B prostatic cancer.

To examine the accuracy of normal pelvic lymph node status in identifying patients with clinical stage B prostatic cancer not having extracapsular tumor extension we reviewed 63 consecutive patients (39 stage B1 and 24 stage B2) treated with radical prostatectomy. Ten per cent of the patients with stage B1 lesions (tumor involving 1 lobe) and 38 per cent with stage B2 lesions (tumor involving both lobes) had extracapsular extension. Extracapsular tumor extension was more common in patients with larger, less differentiated lesions. The results suggest that a negative pelvic lymphadenectomy does not exclude with a high degree of confidence extracapsular tumor extension in patients with clinical stage B2 prostatic cancer.

Genital Neoplasms, Male↗
PubMed1983

Urinary citrate excretion in patients with renal calculi.

Urinary citrate excretion was measured with a specific enzymatic technique in normal subjects and in an unselected group of patients with recurrent calcium oxalate stones. Hypocitraturia (citrate levels less than those present in 95 per cent of the normal population) was detected in 7 of 46 patients with stones (15 per cent). Hypocitraturia was the only metabolic abnormality in 6 patients.

Adult↗
PubMed1983

Ion-chromatographic measurement of oxalate in unprocessed urine.

We describe a sensitive, simple technique for determining urinary oxalate. Urine, diluted as necessary with distilled water, is injected into an ion chromatograph. Oxalate is detected conductimetrically as a distinct peak near the tail of the chromatogram. This peak specifically represents oxalate, because it is abolished if the sample is treated with oxalate decarboxylase. We have used this technique to measure oxalate in more than 3000 consecutively received urine samples. It has a CV of 6%.

Carbonic Acid↗
PubMed1983

Assay of urinary oxalate: six methodologies compared.

To assess how well results by different methods for urinary oxalate determinations agree with each other in a clinical setting, we compared six different assays: Hodgkinson and Williams (Clin Chim Acta 36:127-132, 1972), enzymatic, modified Hodgkinson and Williams, gas chromatography, ion chromatography, and "high-pressure" liquid chromatography. For the entire group of samples, the mean value by each method agreed relatively closely, although the enzymatic procedure produced a somewhat higher value. All six methods had large coefficients of variation within (8-58%) and between (15-88%) assays. In addition, analytical recovery by most assays was more than 100% of the added oxalate. Analytical recovery of 10 micrograms of oxalate added per milliliter of urine specimen ranged from 86 to 237%; for 20 micrograms/mL it was 83 to 320%. Thus for the six methods evaluated, no single method appeared to be superior to the others.

Chromatography, Gas↗
PubMed1983

Evaluation and medical management of the patient with calcium stone disease.

About 80 per cent of renal stones seen in the western hemisphere are composed of calcium and oxalate. The authors discuss some of the metabolic disorders involved in calcium stone disease, describe a comprehensive metabolic work-up for the patient who forms stones recurrently, and suggest some guidelines for treatment.

Adult↗
PubMed1982

Undiverting the ileal conduit.

From 1975 to 1981, 46 patients were evaluated for urinary undiversion. Of these patients 27 completed urinary reconstruction. The patients have been followed for 6 to 80 months, with a mean followup of 32 months and a median followup of 23 months. There has been no death and no rediversion has been necessary, although in 1 patient renal function has deteriorated significantly following urinary reconstruction. Postoperative bladder function was normal in patients diverted for dysfunctional voiding or bladder outlet obstruction but children with meningomyelocele required intermittent catheterization postoperatively. With careful patient selection, meticulous surgical technique and compulsive followup urinary undiversion is a safe procedure.

Adolescent↗
PubMed1982

Oxalate metabolism and renal calculi.

Changes in oxalate excretion (together with changes in urinary volume) constitute the most important factors in altering the probability of renal stone formation. However, investigations on oxalate metabolism have been sparse, perhaps because of the lack of an accurate method for measuring oxalate in biologic fluids. Available data clearly implicate increased urinary oxalate excretion as the etiological factor in stone formation in two groups of patients--those with primary hyperoxaluria and those with gastrointestinal malabsorption. Evidence for the existence of hyperoxaluria in the patient with the "garden" variety of calcium oxalate stones is less persuasive.

Animals↗
PubMed1982

Determination of urinary oxalate by ion chromatography: preliminary observation.

The technique of ion chromatography was applied to determine oxalate concentrations in unprocessed urine. The minimal detectable limits of oxalate was 1 microgram./ml. (11 mumole/liter), the within-run imprecision (Sw) was 2.3 per cent and the total imprecision (St) was 4.9 per cent. Ion chromatography can be used for the simple, accurate and direct measurement of urinary oxalate.

Adult↗
PubMed1981

Receptor-mediated gonadotropin action in the ovary. Demonstration of acute dependence of rat luteal cells on exogenously supplied steroid precursor (sterols) for gonadotropin-induced steroidogenesis.

Incubation of luteal cells with human, horse and rat sera, but not bovine sera resulted in enhanced basal and hCG-stimulated progesterone accumulation. The stimulatory effect of human or rat sera on basal, hCG- or 8 Br-cyclic AMP-induced progesterone synthesis in luteal cells was evident within 15-30 min after incubation, reaching a maximum after 3-4 h. The stimulatory effects of hCG and/or sera were blocked by inhibitors of RNA and protein synthesis. Similarly, lysosomotropic agents, chloroquine (100 microM) and ammonium chloride (10 mM), partly blocked the steroidogenic response of luteal cells to hCG and/or human or rat sera. Incubation of cells in the presence of 2-deoxyglucose, sodium azide and phenylmethylsulfonyl fluoride resulted in partial inhibition of progesterone secretion in response to hCG or sera. Fractionation of human or rat sera into various lipoprotein fractions demonstrated that LDL and HDL most effectively supported and potentiated the steroidogenic response to hCG. Lipoprotein-deficient serum, however, did not alter gonadotropin-induced steroid production. Incubation of luteal cells with increasing concentrations of h-LDL and h-HDL enhanced both basal and hCG-mediated steroidogenesis in a dose-related manner, although very high concentrations of these lipoproteins were inhibitory. Further, [3H]cholesterol from [3H]cholesteryl linoleate-LDL was incorporated into luteal cell progesterone and the extent of this incorporation was enhanced by hCG. Addition of excess unlabeled h-LDL, h-HDL, as well as r-HDL, drastically reduced the incorporation of radioactive label into progesterone. These studies suggest that (a) serum potentiation of steroidogenesis was due to presence of lipoproteins, mainly LDL and HDL, and (b) the lipoprotein-bound cholesterol is delivered into the luteal cells and utilized for steroidogenesis.

Animals↗
PubMed1981

Metabolic studies on the possible mode of action of isoniazid tumorigenicity.

Data on tumorigenicity and mutagenicity of INH show that INH is tumorigenic in mice but not in rats. The metabolic studies on the two species denote that rats are rapid inactivators whereas mice are slow inactivators of INH. Rats are also resistant to the immediate inhibitory effect of INH on DNA biosynthesis. Using Ames test it was observed that INH is mutagenic to salmonella typhimurium strains TA 100 and 1535 and this effect is abolished in presence off 59 mixture. In vivo and in vitro studies on INH interaction with macromolecules reveal that there is a greater interaction with RNA than with DNA and the site of interaction is the cytidine and deoxycytidine, respectively. A preliminary study is undertaken to see if healed TB cases have a higher risk for cancer. It is found that cancer incidence in this group is higher as compared to noncancer patients.

Animals↗
PubMed1981

A comparison of ultrasonography and radiography in the localization of renal calculi: experimental and operative experience.

The capabilities of radiography (mammography film) and ultrasonography (7 MHz. probe) were investigated in cadaver kidneys. Stones of varying size and composition were studied. Clinically, 11 patients then were studied with intraoperative radiography and ultrasonography. Both techniques appeared to localize calculi more than 3 mm. with high consistency in cadaver kidneys and in patients. Real-time B scan ultrasonography is a rapid and accurate technique that has the ability to identify lucent calculi. When used in association with intraoperative radiography, intraoperative ultrasonography can be a great aid in the surgical removal of renal calculi.

Adult↗
PubMed1981

In vitro effect of danazol on luteinizing hormone-releasing hormone-stimulated luteinizing hormone release in rat anterior pituitary cell cultures in vitro.

Monolayer cultures of anterior pituitary glands from female rats were exposed to 5 X 10(-6) M danazol for 0, 4, 24, 48, and 72 h in Dulbecco's Modified Eagle's Medium supplemented with 10% horse serum and 2.5% fetal calf serum. After this treatment, the cell cultures were rinsed and challenged with 10(-8) M LHRH for 6 h. The media were collected and assayed for LH by a hormone-specific RIA using the double antibody precipitation technique. A control incubation was carried out by exposing cell cultures for the same length of time in the absence of danazol but in the presence of 0.5% ethanol in which danazol was dissolved, then challenging the culture with 10(-8) M LHRH, as was done in the experimental group, and assaying the LH released in the medium. The results showed that exposure of cell cultures to danazol caused a significant decrease in LH release in response to LHRH from 13,800 +/- 500 to 3,500 +/- 200 ng/ml. The inhibition of LH release was dependent on both the duration of danazol exposure and its concentration. Danazol exposure had, however, little effect on basal LH secretion by the pituitaries, which remained at about 600 ng/ml at all time points examined. Under the experimental conditions, danazol exerted no effect on the incorporation of amino acid into protein in the cell culture. These results suggest that one of the mechanisms of the antigonadotropic effect of danazol is inhibition of the responsiveness of the pituitary to LHRH-induced LH release.

Animals↗