Ambulatory blood pressure monitoring in pheochromocytoma - paraganglioma: A single center experience

CONTEXT/AIMS

Pheochromocytoma and paraganglioma (PPGL) are rare tumors, and data on ambulatory blood pressure monitoring (ABPM) in these patients and the effect of blocking on ABPM parameters is limited. We aimed to describe ABPM parameters in a cohort of PPGL at our center in western India.

METHODS

Retrospective study of patients with PPGL whose ABPM data was available. Demographic details, secretory status, and ABPM data were retrieved. Coefficient of variability (CV) was calculated as standard deviation/mean in percentage.

RESULTS

In the 39 included patients, mean age at presentation was 39.3 ± 14.2 yr; 20 (51.3%) were males, 25 (64.1%) hypertensive, and mean tumor diameter was 5.3 cm. In 18 patients whose baseline ABPM was done without medications, those with nocturnal blood pressure dipping (6/18, 33%) had higher serum metanephrines (median 313.2 vs. 34.7 pg/ml, P = 0.028). Despite normal office blood pressure (BP), 8.9% of systolic BP readings were >140 mmHg, and 1.2% were >160 mmHg. Among 29 patients with both pre and post-block ABPM, mean BP (systolic 121.6 vs. 132.5 mmHg, P = 0.014; diastolic 68.9 vs. 76.4 mmHg, P = 0.005) and percentage of BP readings above 140 mmHg (median 9.4% vs. 24.4%, P = 0.016) were significantly lowered after the preoperative blockade in hypertensive ( n = 19) patients, whereas CV was similar. The post-blockade ABPM characteristics were similar in patients blocked with amlodipine or prazosin.

CONCLUSION

ABPM provides additional information about BP characteristics in PPGL. The preoperative blocking decreases the magnitude of BP excursions but does not affect BP variability.

Bilateral Internuclear Ophthalmoplegia Caused by Dengue Fever

A 22-year-old male was referred from the medicine department with the chief complaint of double vision for 2 months. The patient had suffered from dengue viral hemorrhagic encephalitis for 2 months for which intensive medical care was given. On ocular examination, both eyes (OU) showed limited adduction with contralateral abducting nystagmus on attempted horizontal gaze. Magnetic resonance imaging of brain showed pontine and midbrain hemorrhages which involved the region of medial longitudinal fasciculus and caused bilateral internuclear ophthalmoplegia (INO). Bilateral INO is very rare and most commonly caused by multiple sclerosis. The presentation of dengue fever causing midbrain and pontine hemorrhages which resulted in bilateral INOs has not been previously reported, to our knowledge.

Comparison of the effectiveness of amblyopia treatment with eye-patch and binocular Occlu-tab for the same treatment duration

Purpose:

This study aimed to compare the conventional eye patch with Occlu-tab—a binocular open-type amblyopia training device—and evaluate their effectiveness in amblyopia treatment.

Methods:

In this prospective, multi-center study, 40 patients between ages 3 to 12 years, diagnosed with anisometropic amblyopia (refraction difference of both eyes ≥ 2 D, best-corrected visual acuity [BCVA] of the amblyopic eye ≤ 0.1 [logMAR]) were treated with Occlu-tab or conventional eye patch for 1 h per day thrice a week. We compared the visual acuity of both groups before and after 6, 7, and 8 weeks of amblyopia treatment. One-way repeated-measures analysis of variance and Tukey’s test were used to compare the visual acuity of both groups pre- and post-treatment.

Results:

Both groups had significantly improved visual acuity at 6, 7, and 8 weeks compared to that before treatment (all P < 0.001). The improvement in BCVA of the Occlu-tab group (0.33 ± 0.25) was significantly greater than that of the eye patch group (0.16 ± 0.17) after 8 weeks of treatment (P = 0.02).

Conclusion:

Amblyopia treatment using binocular open game training with Occlu-tab led to greater improvement in visual acuity than that with a conventional eye patch for the same treatment duration.

Efficacy of supplemental Occlu-pad therapy with partial occlusion in children with refractive anisometropic amblyopia

Purpose:

To study the efficacy of supplemental occlu-pad therapy with partial occlusion in children with refractive anisometropic amblyopia.

Methods:

Thirty-one children who did not improve after partial occlusion of 6 h for 6 months were supplemented with the use of occlu-pad for 1 h per day and three such sessions in a week.

Results:

The mean age was 6.8+/-1.4 years (range 5–9 years). A significant improvement of 3.2+/-1.3 lines in visual acuity was noticed at the end of 3 months of starting this supplemental therapy in children. Out of 31 children, 26 children improved at least 2 lines or more at the end of 3 months. All children (n = 9) having anisohyperopic amblyopia improved at the end of 3 months

Conclusion:

Occlu-pad is useful in supplementing occlusion therapy in cases of refractive amblyopia and is more effective in anisohyperopic amblyopia.

Rhino-orbital-cerebral mucormycosis: An epidemiological study from a tertiary care referral center in Western India

Purpose:

Rhino-orbital-cerebral mucormycosis (ROCM) is a rare opportunistic fungal infection with a fulminant course and an often fatal outcome. It can occur in immune-compromised patients such as those having uncontrolled diabetes, on long-term corticosteroid or immunosuppressive therapy, with COVID-19 infection, renal failure, AIDS, malignancy, or organ transplant. The aim of our study was to study the epidemiology of mucormycosis in COVID-19 patients and identify its risk factors.

Methods:

Ours was an epidemiological study wherein we gathered the demographic, clinical, histopathological, and radiological data of 458 patients of mucormycosis who presented to us between August 2020 and May 2021. Mucormycosis was defined through clinical and radiological findings or positive culture reports.

Results:

Out of all, 20.74% of patients did not have any past or concurrent history of COVID-19. The most common symptom of mucormycosis was orbital/facial pain (38.64%) and the most common sign was periocular/facial edema (50.74%). Mucormycosis involving the nose and sinuses (94.54%) was most common followed by rhino-orbital (45.41%) and brain involvement (10.04%). The most common risk factor for mucormycosis was diabetes [81.92%], followed by corticosteroid use [79.69%] and supplemental oxygen [48.90%]. Most of the patients received similar treatment with IV amphotericin B [88.64%] and local debridement [80.74%]

Conclusion:

With the third wave of COVID-19 still lurking, a fatal fungal infection should be kept in mind in COVID-19 active as well as recovered patients, especially those who have co-morbid medical conditions such as uncontrolled diabetes and who are treated with large doses of corticosteroids.

Epidemiology, clinical profile, management, and outcome of COVID-19-associated rhino-orbital-cerebral mucormycosis in 2826 patients in India - Collaborative OPAI-IJO Study on Mucormycosis in COVID-19 (COSMIC), Report 1

Purpose

COVID-19-associated rhino-orbital-cerebral mucormycosis (ROCM) has reached epidemic proportion during India's second wave of COVID-19 pandemic, with several risk factors being implicated in its pathogenesis. This study aimed to determine the patient demographics, risk factors including comorbidities, and medications used to treat COVID-19, presenting symptoms and signs, and the outcome of management.

Methods

This was a retrospective, observational study of patients with COVID-19-associated ROCM managed or co-managed by ophthalmologists in India from January 1, 2020 to May 26, 2021.

Results

Of the 2826 patients, the states of Gujarat (22%) and Maharashtra (21%) reported the highest number of ROCM. The mean age of patients was 51.9 years with a male preponderance (71%). While 57% of the patients needed oxygen support for COVID-19 infection, 87% of the patients were treated with corticosteroids, (21% for > 10 days). Diabetes mellitus (DM) was present in 78% of all patients. Most of the cases showed onset of symptoms of ROCM between day 10 and day 15 from the diagnosis of COVID-19, 56% developed within 14 days after COVID-19 diagnosis, while 44% had delayed onset beyond 14 days. Orbit was involved in 72% of patients, with stage 3c forming the bulk (27%). Overall treatment included intravenous amphotericin B in 73%, functional endoscopic sinus surgery (FESS)/paranasal sinus (PNS) debridement in 56%, orbital exenteration in 15%, and both FESS/PNS debridement and orbital exenteration in 17%. Intraorbital injection of amphotericin B was administered in 22%. At final follow-up, mortality was 14%. Disease stage >3b had poorer prognosis. Paranasal sinus debridement and orbital exenteration reduced the mortality rate from 52% to 39% in patients with stage 4 disease with intracranial extension (p < 0.05).

Conclusion

: Corticosteroids and DM are the most important predisposing factors in the development of COVID-19-associated ROCM. COVID-19 patients must be followed up beyond recovery. Awareness of red flag symptoms and signs, high index of clinical suspicion, prompt diagnosis, and early initiation of treatment with amphotericin B, aggressive surgical debridement of the PNS, and orbital exenteration, where indicated, are essential for successful outcome.

Thoracoscopic oesophageal atresia/tracheo-oesophageal fistula (OA/TOF) repair is associated with a higher stricture rate: a single institution’s experience

PURPOSE

Thoracoscopic OA/TOF repair was first described in 1999. Currently, less than 10% of surgeons routinely employ minimally access surgery. Our primary aim was to review our immediate-, early- and long-term outcomes with this technique compared with the open approach.

METHODS

A retrospective review of all patients undergoing primary OA/TOF (Type C) repair at our institution from 2009 was conducted. Outcome measures included length of surgery, conversion rate from thoracoscopy, early complications such as anastomotic leak and post-operative complications such as anastomotic strictures needing dilatations. Fisher's exact and Kruskal-Wallis tests were used for statistical analysis.

RESULTS

95 patients in total underwent OA/TOF repair during the study period of which 61 (64%) were completed via an open approach. 34 were attempted thoracoscopically of which 11 (33%) were converted. There was only one clinically significant anastomotic leak in our series that took place in the thoracoscopic group. We identified a significantly higher stricture rate in our thoracoscopic cohort (72%) versus open surgery (43%, P < 0.05). However, the median number of dilations (3) performed was not significantly different between the groups. There was one recurrent fistula in the thoracoscopic converted to open group. Our median follow-up was 60 months across the groups.

CONCLUSION

In our experience, the clinically significant leak rate for both open and thoracoscopic repair as well as recurrent fistula is much lower than has been reported in the literature. We do not routinely perform contrast studies and are, thus, reporting clinically significant leaks only. The use of post-operative neck flexion, ventilation and paralysis is likely to be protective towards a leak. Thoracoscopic OA/TOF repair is associated with a higher stricture rate compared with open surgery; however, these strictures respond to a similar number of dilatations and are no more refractory. Larger, multicentre studies may be useful to investigate these finding further.

Ultrasonographic Features of Ulnar Nerve Affected by Hansen's Disease

Leprosy continues to be a major public health problem in some areas of our country. It predominantly afflicts peripheral nerves and skin and may lead to deformities. Social stigma as a result of deformities further plagues the situation. Prompt and early diagnosis coupled with adequate treatment, concurrent rehabilitative strategies if deformities do occur, and health education help to control the problem. Definitive diagnosis of leprosy has traditionally been based on assessment of slit skin smears (SSS) after AFB-staining and characteristic histopathology after biopsyof the lesion. However, recently, thickening of the peripheral nerves has been demonstrated by ultrasonography and this can be used as a sensitive tool to assess and measure enlargement of peripheral nerves, which are hallmarks for leprosy especially in clinical settings. In this report, the ultrasonographic findings of ulnar nerve enlargement due to leprosy in a fourteen-year-old male patient are described.

Tryptophan-NAD+ pathway metabolites as putative biomarkers and predictors of peroxisome proliferation

The present study was designed to provide further information about the relevance of raised urinary levels of N-methylnicotinamide (NMN), and/or its metabolites N-methyl-4-pyridone-3-carboxamide (4PY) and N-methyl-2-pyridone-3-carboxamide (2PY), to peroxisome proliferation by dosing rats with known peroxisome proliferator-activated receptor alpha (PPARalpha) ligands [fenofibrate, diethylhexylphthalate (DEHP) and long-chain fatty acids (LCFA)] and other compounds believed to modulate lipid metabolism via PPARalpha-independent mechanisms (simvastatin, hydrazine and chlorpromazine). Urinary NMN was correlated with standard markers of peroxisome proliferation and serum lipid parameters with the aim of establishing whether urinary NMN could be used as a biomarker for peroxisome proliferation in the rat. Data from this study were also used to validate a previously constructed multivariate statistical model of peroxisome proliferation (PP) in the rat. The predictive model, based on 1H nuclear magnetic resonance (NMR) spectroscopy of urine, uses spectral patterns of NMN, 4PY and other endogenous metabolites to predict hepatocellular peroxisome count. Each treatment induced pharmacological (serum lipid) effects characteristic of their class, but only fenofibrate, DEHP and simvastatin increased peroxisome number and raised urinary NMN, 2PY and 4PY, with simvastatin having only a transient effect on the latter. These compounds also reduced mRNA expression for aminocarboxymuconate-semialdehyde decarboxylase (ACMSDase, EC 4.1.1.45), the enzyme believed to be involved in modulating the flux of tryptophan through this pathway, with decreasing order of potency, fenofibrate (-10.39-fold) >DEHP (-3.09-fold) >simvastatin (-1.84-fold). Of the other treatments, only LCFA influenced mRNA expression of ACMSDase (-3.62-fold reduction) and quinolinate phosphoribosyltransferase (QAPRTase, EC 2.4.2.19) (-2.42-fold) without any change in urinary NMN excretion. Although there were no correlations between urinary NMN concentration and serum lipid parameters, NMN did correlate with peroxisome count (r2=0.63) and acyl-CoA oxidase activity (r2=0.61). These correlations were biased by the large response to fenofibrate compared to the other treatments; nevertheless the data do indicate a relationship between the tryptophan-NAD+ pathway and PPARalpha-dependent pathways, making this metabolite a potentially useful biomarker to detect PP. In order to strengthen the observed link between the metabolites associated with the tryptophan-NAD+ pathway and more accurately predict PP, other urinary metabolites were included in a predictive statistical model. This statistical model was found to predict the observed PP in 26/27 instances using a pre-determined threshold of 2-fold mean control peroxisome count. The model also predicted a time-dependent increase in peroxisome count for the fenofibrate group, which is important when considering the use of such modelling to predict the onset and progression of PP prior to its observation in samples taken at autopsy.

Differential expression of the lenticular antioxidant system in laboratory animals: a determinant of species predilection to oxidative stress-induced ocular toxicity?

PURPOSE

Various animal species have been used to study oxidative stress-induced cataractogenesis; however, given that differences in the expression of the lens antioxidant system may influence species susceptibility to oxidative stress, we compared and contrasted a broad spectrum of components of the lens antioxidant system in dog, rat, marmoset, and rabbit.

METHODS

Lenses collected from beagle dogs, Sprague-Dawley rats, marmosets, and New Zealand white rabbits were assayed for reduced glutathione (GSH), and activities of copper-zinc and manganese superoxide dismutase (CuZn-SOD; Mn-SOD), catalase (CAT), glutathione peroxidase (GPX), gamma-Glutamylcysteine synthetase (GCS), glutathione reductase (GR), glutathione-S-transferases (GST), and glucose-6-phosphate dehydrogenase (GPDH), and Trolox equivalent antioxidant capacity (TEAC).

RESULTS

Expression of the lens antioxidant system varied considerably between species. Marmoset lens contained the highest levels of GSH, its respective biosynthetic and recycling enzymes GCS and GR, and the associated H(2 )O(2)-dismutation enzyme GPX. Activities of both SOD isoforms were also highest in marmoset lens. However, activities of the xenobiotic-conjugating enzyme GST and NADPH-generating enzyme GPDH were relatively low. In contrast, dog lens had the lowest levels of GSH, GCS, GR, and Cu-Zn SOD (1/2, 1/2 and 1/33, and 1/63 that in marmoset) but highest levels of GST and GPDH. Rabbit lens contained the highest CAT activity, at up to 3.5-fold that for marmoset and rat.

CONCLUSION

These results demonstrate substantial variation in lens antioxidant systems between different laboratory animal species. Given that such variation may affect relative susceptibility to oxidative stress-mediated ocular toxicity, our findings may provide useful information when choosing different animal species for lens research.

Effect of diquat on the antioxidant system and cell growth in human neuroblastoma cells

Oxidative stress elicits an adaptive antioxidant response, which varies with tissue type. Diquat, a potent redox cycler that generates reactive oxygen species, has been used to study oxidative stress; however, its effect on the antioxidant system has not been characterized in neuronal cells. Accordingly, we measured antioxidant parameters and cell growth in human neuroblastoma SH-SY5Y cells cultured for 48 h in medium containing 5, 10, or 25 microM diquat dibromide or phosphate-buffered saline. Viable cells were assayed for glutathione (GSH) and activities of catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), glutathione peroxidase (GPX), and glucose-6-phosphate dehydrogenase (GPDH). Mitochondrial function was evaluated by glutamate dehydrogenase (GDH) activity and MTT reduction. Diquat caused a marked concentration-related decrease in viable cell count ( by 26, 51, and 87% at 5, 10, and 25 microM diquat). Cell viability was only affected at 10 and 25 microM diquat and did not fully account for the decreased viable cell count. Concentration-related increases also occurred with GSH levels and a majority of antioxidant enzymes activities; however, the mode and magnitude varied with parameter. Increases in GSH, CAT, SOD, and GR were maximal at 25 microM diquat (to 3-, 6-, 2-, and 1.5-fold control values, respectively). GPDH activity was maximal at 10 microM diquat and then decreased to 86% of control activity at 25 microM diquat. GPX activity showed a concentration-related decrease (to 35% of control). Activity of the mitochondrial enzyme GDH increased 3-fold at 25 microM diquat, along with a lesser increase in MTT reduction. We conclude that diquat reduces cell growth in neuroblastoma cells and induces an adaptive antioxidant response, which are concentration dependent and occur at sublethal concentrations. At higher concentrations, diquat alters mitochondrial function and becomes increasingly toxic.

Pro-survival function of Akt/protein kinase B in prostate cancer cells. Relationship with TRAIL resistance

Tumor necrosis factor superfamily member TRAIL/Apo-2L has recently been shown to induce apoptosis in transformed and cancer cells. Some prostate cancer cells express constitutively active Akt/protein kinase B due to a complete loss of lipid phosphatase PTEN gene, a negative regulator of phosphatidylinositol 3-kinase pathway. Constitutively active Akt promotes cellular survival and resistance to chemotherapy and radiation. We have recently noticed that some human prostate cancer cells are resistant to TRAIL. We therefore examined the intracellular mechanisms of cellular resistance to TRAIL. The cell lines expressing the highest level of constitutively active Akt were more resistant to undergo apoptosis by TRAIL than those expressing the lowest level. Down-regulation of constitutively active Akt by phosphatidylinositol 3-kinase inhibitors, wortmannin and LY294002, reversed cellular resistance to TRAIL. Treatment of resistant cells with cycloheximide (a protein synthesis inhibitor) rendered cells sensitive to TRAIL. Transfecting dominant negative Akt decreased Akt activity and increased TRAIL-induced apoptosis in cells with high Akt activity. Conversely, transfecting constitutively active Akt into cells with low Akt activity increased Akt activity and attenuated TRAIL-induced apoptosis. Inhibition of TRAIL sensitivity occurs at the level of BID cleavage, as caspase-8 activity was not affected. Enforced expression of anti-apoptotic protein Bcl-2 or Bcl-X(L) inhibited TRAIL-induced mitochondrial dysfunction and apoptosis. We therefore identify Akt as a constitutively active kinase that promotes survival of prostate cancer cells and demonstrate that modulation of Akt activity, by pharmacological or genetic approaches, alters the cellular responsiveness to TRAIL. Thus, TRAIL in combination with agents that down-regulate Akt activity can be used to treat prostate cancer.

Constitutively active Akt is an important regulator of TRAIL sensitivity in prostate cancer

TRAIL/Apo-2L is a member of the tumor necrosis factor superfamily and has recently been shown to induce apoptosis in cancer cells, but not in normal cells. In nude mice injected with human tumors, TRAIL reduces the size of these tumors without side effects. Akt promotes cell survival and block apoptosis. Some prostate cancer cells express high levels of Akt due to lack of active lipid phosphatase PTEN, a negative regulator of PI-3 kinase pathway, which may be responsible for drug resistance. The objective of this paper is to investigate the intracellular molecules that regulate TRAIL resistance. We have examined caspase-8 activity, BID cleavage, Akt activity, mitochondrial membrane potential (DeltaPsi(m)) and apoptosis in prostate cancer (LNCap, PC-3, PC-3M and DU145) cells treated with or without TRAIL. PC-3, PC-3M and DU145 cells are sensitive to TRAIL, whereas LNCap cells are resistant. LNCap cells express the highest level of constitutively active Akt, which is directly correlated with TRAIL resistance. TRAIL activates caspase-8 in all the cell lines. Downregulation of constitutively active Akt by PI-3 kinase inhibitors (wortmannin and LY-294002), dominant negative Akt or PTEN, renders LNCap cells sensitive to TRAIL. Inhibition of TRAIL sensitivity occurs at the level of BID cleavage. Inhibition of protein synthesis by cycloheximide also causes LNCap cells sensitive to TRAIL. Overexpression of Bcl-2 or Bcl-X(L) inhibits TRAIL-induced DeltaPsi(m) and apoptosis. Overexpression of constitutively active Akt in PC-3M cells (express very low levels of constitutively active Akt) restores TRAIL resistance. These data suggest that elevated Akt activity protects LNCap cells from TRAIL-induced apoptosis, and the PI-3 kinase/Akt pathway may inhibit apoptotic signals by inhibiting processing of BID. Thus, constitutively active Akt is an important regulator of TRAIL sensitivity in prostate cancer.

Progressive renal disease: does the quality of the proteinuria matter or only the quantity?

Proteinuria is now accepted to be not just a sign of renal disease but also a contributory factor to the development of progressive tubulointerstitial fibrosis. Excellent correlations between the degree of proteinuria and rate of decline of glomerular filtration rate have been demonstrated. What has been investigated less is whether the type of protein found in the urine is important. Using transformed and primary human proximal tubular epithelial cells, we have investigated the binding of albumin and retinol binding protein to plasma membrane preparations and studied the response of the intact cells to increasing concentrations of these same proteins. We have preliminary evidence for differences in the pattern of binding of these two proteins to the plasma membrane receptors and also for differential release of pro-inflammatory cytokines from intact cells. These in vitro results, along with those of other groups, and some recent clinical findings suggest that the quality of proteinuria may play a role in the early development of interstitial fibrosis. Furthermore, the use of such in vitro model systems based on human proximal epithelial cell culture can provide a means of evaluating the potential significance of different markers of tubular damage.

Reference ranges for plasma cystatin C and creatinine measurements in premature infants, neonates, and older children

AIM

To establish a reference range in the paediatric population for the new glomerular filtration rate (GFR) marker, cystatin C, and to compare it with that of creatinine.

METHODS

Cystatin C and creatinine were measured by particle enhanced nephelometric immunoassay (PENIA) and fixed interval Jaff¿e methods, respectively, in 291 children aged 1 day to 17 years, including 30 premature infants with gestational ages ranging from 24 to 36 weeks.

RESULTS

In the premature infants, concentrations of both cystatin C and creatinine were significantly raised compared with term infants, with cystatin C concentrations being between 1.10 and 2.06 mg/litre and creatinine between 32 and 135 micromol/litre. In premature infants, there was no significant relation between gestational age and cystatin C or creatinine concentration. Creatinine concentrations fell to a nadir at 4 months of age, rising gradually to adult values by about 15-17 years of age, in contrast to cystatin C, which fell to a mean concentration of 0.80 mg/litre by the 1st year of life, and remained constant throughout adulthood up to the age of 50 years. Neither analyte showed any influence of sex.

CONCLUSION

The measurement of cystatin C, rather than creatinine, is more practical for monitoring GFR changes in the paediatric population.

The use of optical sensors to understand cellular interactions with renal cells

Optical biosensor technology has revolutionized the assessment of receptor binding, enabling the characterization of low affinity interactions in real time. We report the application of the LAsys Optical Biosensor to the investigation of the affinity and specificity of the putative proximal tubular scavenging receptor for protein reabsorption and the specificity of AGE-modified protein interactions with primary human mesangial cells. Using the LLCPK cell line, the carboxy-methyl dextran cuvette surface and five different proteins (ranging in size and charge), we have shown that there is evidence to support the existence of a single scavenging receptor for all the proteins tested. The proteins competed with each other differing only in their relative binding affinity for the common receptor. We have also shown that human mesangial cells can bind to AGE-modified human serum albumin (AGE-HSA) immobilized onto the carboxylate surfaced planar cuvette and that binding can be inhibited using increasing concentrations of soluble AGE-HSA. However, increasing concentrations of soluble Non-AGE modified HSA can also inhibit binding to a similar extent which implies that there is relatively little AGE-receptor (RAGE) expression on cultured primary human mesangial cells. These results demonstrate the exciting potential of this technology as a tool to explore cellular interactions with renal cells.

Measurement of the kinetics of protein uptake by proximal tubular cells using an optical biosensor

BACKGROUND

The affinity and specificity of protein reabsorption by proximal tubular cells have been investigated using techniques for monitoring endocytosis, demonstrating a high capacity but low affinity process. It is not known whether uptake is through binding to a single binding site/receptor with differing affinities, or if there are several classes of binding sites receptors, each specific for differing proteins or groups, such as, high or low molecular weight proteins.

METHODS

We have developed a novel technique for analyzing the kinetics of protein binding to tubular cells using a optical biosensor system. We have studied the binding of cultured LLCPK cells to albumin and RBP immobilized onto the sensor. By adding increasing concentrations of competing proteins [varying in molecular weight from 66,000 to 11,800 D and pI from 4.6 to 9.2 as represented by albumin, alpha1-microglobulin (alpha1M), retinol binding protein (RBP), cystatin C and beta2-microglobulin (beta2m)], specific and inhibitable cell binding was demonstrated.

RESULTS

Equilibrium constants, KA, could be calculated from the reciprocal of the protein concentration causing 50% inhibition in binding rate. These were: albumin = 8.0 x 10(4) M(-1), alpha1M = 2.0 x 10(5) M(-1), RBP = 2.7 x 10(4) M(-1), cystatin C = 2.0 x 10(4) M(-1), beta2m = 4.2 x 10(3) M(-1). There were no significant differences between the measured KA's whether RBP or albumin were immobilized on the surface.

CONCLUSIONS

All the proteins gave similar shaped inhibition profiles, suggesting that there is one binding site/receptor for all proteins studied, regardless of molecular weight or charge, but there are differing affinities for each protein.

Development and validation of an automated latex-enhanced immunoassay for prealbumin

The measurement of circulating prealbumin has been shown to be clinically useful in the assessment of nutritional status, both as an initial screen and in the monitoring of nutritional recovery. We describe a fully automated, noncompetitive, homogeneous, light-scattering immunoassay that has been developed for this analyte on a Dimension (Dade) analyzer. A sheep anti-prealbumin IgG fraction was covalently coupled to 40-nm chloromethyl styrene particles and, after the addition of sample, polyethylene glycol-assisted immunoagglutination was monitored by turbidimetry. The prealbumin working assay range was 8-550 mg/L at a sample volume of 2 microL and a reaction time of 6.5 min. When data were analyzed using ANOVA, total and within-run assay imprecision values (CVs) were 1-5%, and calibration and reagent stabilities were in excess of 40 days. Mean analytical recoveries were 102% +/- 4% (SD), and there was no lack of parallelism. Hemolysis, lipemia, and bilirubin did not interfere. Both plasma anticoagulated with heparin or EDTA and serum from plain or serum-separation tubes were acceptable as sample matrices. Comparison with the Beckman Array method gave a Passing and Bablok regression of: Dimension analyzer = 1.01Beckman + 7.1 (n = 103), using a common calibrator. We conclude that the prealbumin method is appropriate for clinical use according to the analytical criteria used in this study.

Development and validation of an automated latex-enhanced immunoassay for prealbumin

The measurement of circulating prealbumin has been shown to be clinically useful in the assessment of nutritional status, both as an initial screen and in the monitoring of nutritional recovery. We describe a fully automated, noncompetitive, homogenous, light-scattering immunoassay that has been developed for this analyte on a Dimension® (Dade) analyzer. A sheep anti-prealbumin IgG fraction was covalently coupled to 40-nm chloromethyl styrene particles and, after the addition of sample, polyethylene glycol-assisted immunoagglutination was monitored by turbidimetry. The prealbumin working assay range was 8–550 mg/L at a sample volume of 2 μL and a reaction time of 6.5 min. When data were analyzed using ANOVA, total and within-run assay imprecision values (CVs) were 1–5%, and calibration and reagent stabilities were in excess of 40 days. Mean analytical recoveries were 102% ± 4% (SD), and there was no lack of parallelism. Hemolysis, lipemia, and bilirubin did not interfere. Both plasma anticoagulated with heparin or EDTA and serum from plain or serum-separation tubes were acceptable as sample matrices. Comparison with the Beckman Array® method gave a Passing and Bablok regression of: Dimension analyzer = 1.01Beckman + 7.1 (n = 103), using a common calibrator. We conclude that the prealbumin method is appropriate for clinical use according to the analytical criteria used in this study.

Measurement of albumin and low molecular weight proteins in the urine of newborn infants using a cotton wool ball collection method

OBJECTIVE

The aim of this study was to investigate the inter-relationship between urinary excretion of alpha-1-microglobulin (A1M), retinol-binding protein (RBP) and albumin in term and premature neonates, with urine collected into cotton wool balls and extracted by a novel method.

SUBJECTS AND METHODS

Sixty-four infants were studied on the first day of life; 26 had been born at term (37-42 weeks gestation) and 38 prematurely (24-28 weeks n = 16, 29-36 weeks n = 22). Urine collected into cotton wool balls was analysed following a new detergent extraction method, which resulted in a recovery rate of 94-107% for albumin. A1M, RBP and creatinine.

RESULTS

Urinary protein excretion, expressed as a ratio to urinary creatinine, decreased significantly with increasing gestational age (24-28 weeks, 29-36 weeks, 37-42 weeks: albumin:creatinine ratio mg/mmol mean 96.9, 31.7, 19.3; A1M:creatinine ratio mg/mmol mean 99.3, 37.0, 7.8; RBP:creatinine ratio mg/mmol mean 16.2, 3.8, and < 0.01, below the limit of detection, respectively). When results were corrected for birthweight, this gestation-associated effect was still present for A1M and RBP, but not for albumin. In premature infants there was a significant positive correlation between A1M:creatinine ratio and RBP:creatinine ratio (r = 0.85), and also between albumin and both A1M and RBP (r = 0.82 and 0.77).

CONCLUSION

Increased excretion of A1M, RBP and albumin at earlier gestational ages is probably due to proximal tubular immaturity, although tubular damage and also glomerular dysfunction cannot be excluded as possible explanations.

A simple, automated, nonextraction assay for serum digoxin using particle-enhanced immunoassay

We have adapted a latex particle-enhanced immunoassay for serum digoxin to a centrifugal analyser. A 4-microliter serum sample (without pretreatment) inhibits the monoclonal antibody induced aggregation of digoxin-coated latex particles. The total assay time is 10 min and mean analytical recoveries were 98.1%. Intra and interassay precision were < 4.2 and < 15.0%, respectively. Method comparison with an established fluorescence polarisation immunoassay (FPIA) gave R = 0.97, and a Deming regression analysis of particle-enhanced turbidimetric inhibition immunoassay (PETINIA) = FPIA x 0.78 + 0.007 microgram/L (n = 91). There was no evidence of significant interference from digoxin-like immunoreactive compounds in patients with chronic renal failure. This assay can be adapted to most photometric analysers used in routine laboratories and is a significant advance in the sensitivity of latex particle-enhanced immunoassays in a serum matrix.

Development and validation of a particle-enhanced turbidimetric inhibition assay for urine albumin on the Dade aca® analyzer

The measurement of urine albumin now has a well-established role in the monitoring of patients with diabetes mellitus. We have developed a particle-enhanced immunoturbidimetric inhibition assay for urine albumin on the Dade aca® analyzer. The inhibition approach removes any of the potential antigen excess difficulties that could be expected from the wide clinical range of urine albumin, but retains the sensitivity advantages of latex-enhanced immunoturbidimetry. Human serum albumin (HSA) is covalently attached to 40-nm poly(chloromethyl)styrene-modified latex particles. This reagent, along with monoclonal antibody to HSA, is aliquoted into the aca reagent pack along with polyethylene glycol 8000 in a tablet form (giving a final reaction concentration of 15 g/L). A 150 mmol/L phosphate buffer, pH 7.8, is used to fill the reagent pack in the instrument and the agglutination reaction is monitored at 340 nm. The sample volume is 100 μL and the calibration curve covers the range 2–250 mg/L. Evaluation of commercial scale reagents against the Beckman Array nephelometric immunoassay system gave a Deming regression correlation of aca = 0.87 × Beckman + 8.5,r = 0.995, n = 145. Mean analytical recovery was 104 ± 4.5%, n = 20, and there was no evidence of a lack of parallelism. Interassay precision was 8.8% at 10.0 mg/L and &lt;2.5% at &gt;65 mg/L. Calibrator stability was in excess of 60 days. A small reference range study (24-h urine collections, n = 27) gave a mean of 5.6 mg/L with a range of 0.5–16.2 mg/L. Analytical sensitivity (2.5 SD from zero) was 0.40 mg/L.

Development and validation of a particle-enhanced turbidimetric inhibition assay for urine albumin on the Dade aca analyzer

The measurement of urine albumin now has a well-established role in the monitoring of patients with diabetes mellitus. We have developed a particle-enhanced immunoturbidimetric inhibition assay for urine albumin on the Dade aca analyzer. The inhibition approach removes any of the potential antigen excess difficulties that could be expected from the wide clinical range of urine albumin, but retains the sensitivity advantages of latex-enhanced immunoturbidimetry. Human serum albumin (HSA) is covalently attached to 40-nm poly(chloromethyl)styrene-modified latex particles. This reagent, along with monoclonal antibody to HSA, is aliquoted into the aca reagent pack along with polyethylene glycol 8000 in a tablet form (giving a final reaction concentration of 15 g/L). A 150 mmol/L phosphate buffer, pH 7.8, is used to fill the reagent pack in the instrument and the agglutination reaction is monitored at 340 nm. The sample volume is 100 microL and the calibration curve covers the range 2-250 mg/L. Evaluation of commercial scale reagents against the Beckman Array nephelometric immunoassay system gave a Deming regression correlation of aca = 0.87 x Beckman + 8.5, r = 0.995, n = 145. Mean analytical recovery was 104+/-4.5%, n = 20, and there was no evidence of a lack of parallelism. Interassay precision was 8.8% at 10.0 mg/L and <2.5% at >65 mg/L. Calibrator stability was in excess of 60 days. A small reference range study (24-h urine collections, n = 27) gave a mean of 5.6 mg/L with a range of 0.5-16.2 mg/L. Analytical sensitivity (2.5 SD from zero) was 0.40 mg/L.

Electronic self-help and support groups

OBJECTIVES

The authors examined the impact of a voice bulletin board on the following: (1) participation in self-help efforts, (2) expression of emotional support, (3) development of solidarity within the group, (4) utilization of health-care services, and (5) health status of subjects.

METHODS

Subjects were 53 pregnant women who abused drugs. A quasi-experimental design with matched control group and observations before and after intervention were carried out. Clients in the control group were asked to participate in biweekly face-to-face meetings. Clients in the experimental group participated in the voice bulletin board. Experimental subjects had previous experience with computer services. Subjects reported their level of drug use, health status, and utilization of health services. They also reported on their symptoms, attitudes toward use of physician services, loneliness, willingness to disclose information in groups, and sense of solidarity with their group. The content of the communication among the experimental group was recorded and the utterances were classified as to the type of communication. Exit interviews were done 4 months after baseline interviews were conducted. Clients were paid to complete the baseline and the exit questionnaires, and 94% completed the exit questionnaires. The dependent variables were utilization or health status at exit; the co-variate was utilization or health status at baseline; and the independent variable was the group in which the subject participated.

RESULTS

Clients were eight times more likely to participate in the voice bulletin board than in the face-to-face meeting (alpha < 0.01). The majority of the comments left on the bulletin board (54.6%) were for emotional support of each other; no "flaming" or overt disagreements occurred. The more clients participated in the voice bulletin board, the more they felt a sense of solidarity with each other (alpha < 0.001). Members of the experimental group reported significantly lower rates of visiting outpatient clinics than members of the control group (alpha < 0.05). Lower utilization did not lead to poor health status or more drug use: There were no statistically significant differences in the health status and drug use between the experimental and the control groups.

CONCLUSIONS

Voice bulletin boards may be an effective method of providing support to mothers who have a history of drug use. Use of these services may lead to lower cost without worsening patients' health.

Use of urine albumin measurement as a replacement for total protein

We have investigated the replacement of urine total protein estimations for the assessment of glomerular permeability, by the measurement of urine albumin excretion using a latex particle enhanced immunoturbidimetric assay. An initial screen was performed using Albustix to assess the sample pre-dilution necessary for immunoanalysis. A total of 167 24-hour urine samples were analysed and urine albumin concentration correlated well with that of urine total protein (r = 0.93) over the range 0-16,800 mg/l. This protocol provides a more cost effective and analytically valid assessment of glomerular permeability.

Serum cystatin C measured by automated immunoassay: a more sensitive marker of changes in GFR than serum creatinine

Serum cystatin C has been suggested as a new marker of GFR. For the introduction of this marker into clinical use a rapid and automated method is required. We have developed and validated an assay for serum cystatin C using latex particle-enhanced immunoturbidimetry. Intra- and inter-assay precision were < 3% and < 5% across the assay range. Analytical recovery was 93 +/- 3.8% and no lack of parallelism was demonstrated. Regression analysis of a method comparison with an enzyme-enhanced radial-immunodiffusion method, gave PETIA = 0.074 + 0.93 x SRID, r = 0.98, N = 100. Inter-assay precision profiles showed cystatin C was measured with two-fold better precision than creatinine on the same analyzer. Cystatin C measurement was neither interfered with by icterus nor by hemolysis. 1/cystatin C versus 1/creatinine concentrations gave r = 0.67, N = 469. Comparison of Cr EDTA GFR with 1/cystatin C and 1/creatinine gave r = 0.81 and 0.50, respectively, N = 206. Calculating diagnostic sensitivity for abnormal GFR showed cystatin C to be significantly (P < 0.05) more sensitive than creatinine (71.4 vs. 52.4%). Cystatin C measurement using PETIA technology can be automated on the same instruments used routinely for the measurement of creatinine and offers better analytical performance and probably improved clinical sensitivity as a screening test for early renal damage.

Hyperandrogenism in polycystic ovary syndrome. Evidence of dysregulation of 11 beta-hydroxysteroid dehydrogenase

BACKGROUND

Hyperandrogenemia is the hallmark of the polycystic ovary syndrome, yet the relative contributions of the adrenal cortex and ovary to the overproduction of androgen remain unclear. To identify possible causes of adrenocortical overactivity, we studied the metabolism of adrenal and ovarian steroid hormones in women with this disorder.

METHODS

We measured 24-hour urinary excretion of steroid hormone metabolites by high-resolution capillary gas chromatography in 65 women with the polycystic ovary syndrome and 45 normal women matched for body-mass index.

RESULTS

After adjustment for body-mass index, the urinary excretion of testosterone and androstenedione metabolites was 1.9 times higher in the women with the syndrome than in the normal women, and the excretion of dehydroepiandosterone metabolites (C19 steroid sulfates) and cortisol metabolites was 1.5 and 1.3 times higher, respectively (P < 0.01 for all comparisons). The affected women also had significantly higher ratios of 11-oxo (oxygenated) metabolites to 11-hydroxy metabolites of cortisol (1.4 times higher, P < 0.001) and of 11-oxo to 11-hydroxy metabolites of corticosterone (1.8 times higher, P < 0.001). In the group with the polycystic ovary syndrome, 55 percent of the nonobese women and 24 percent of the obese women had ratios above the upper limit of normal; the ratios in the obese women did not differ significantly from those in the nonobese women.

CONCLUSIONS

Adrenal secretion of cortisol and androgens is increased in women with the polycystic ovary syndrome. The increases may be explained by dysregulation of 11 beta-hydroxysteroid dehydrogenase causing increased oxidation of cortisol to cortisone, which cannot be accounted for by obesity.

Stabilization of turbidimetric immunoassay by covalent coupling of antibody to latex particles

Turbidimetric immunoassay is commonly used to quantify serum proteins. Latex-particle enhancement of this type of assay has been primarily associated with increasing assay sensitivity. However, covalent coupling of an antibody to a latex particle can offer other advantages that are also pertinent in measurement of high concentrations of analytes. By using a common antibody with IgG as a model analyte, we describe the development of a nonenhanced and a latex-particle-enhanced turbidimetric assay for measuring serum IgG. Both assays show adequate analytical recovery and parallelism, and results compare well with those by rate nephelometry. The latex-enhanced assay has equivalent sensitivity, working range, and interassay precision, but much greater signal change and calibration stability than the nonenhanced assay. In addition, with latex particles, less antiserum is needed. Coupling antibodies to latex particles offers considerable advantages, even when an improved assay detection limit is not required.

Development of a rapid latex enhanced turbidimetric assay for retinol binding protein in urine

We describe a simple, rapid and sensitive homogeneous immunoassay for urinary retinol-binding protein (RBP) using latex particle-enhanced turbidimetric immunoassay. Rabbit anti-human RBP is covalently coupled to 40 nm latex particles and the assay performed on the IL Monarch 2000 centrifugal analyser, with a 20 microL sample volume and the reaction monitored at 340 nm over an 8 min period. The assay range is 0-6 mg/L with a detection limit of 25 micrograms/L. The within and between assay coefficients of variation are less than 1.5% and less than 2.5%, respectively. Comparison with radioimmunoassay for RBP showed good agreement.

Stabilization of turbidimetric immunoassay by covalent coupling of antibody to latex particles

Turbidimetric immunoassay is commonly used to quantify serum proteins. Latex-particle enhancement of this type of assay has been primarily associated with increasing assay sensitivity. However, covalent coupling of an antibody to a latex particle can offer other advantages that are also pertinent in measurement of high concentrations of analytes. By using a common antibody with IgG as a model analyte, we describe the development of a nonenhanced and a latex-particle-enhanced turbidimetric assay for measuring serum IgG. Both assays show adequate analytical recovery and parallelism, and results compare well with those by rate nephelometry. The latex-enhanced assay has equivalent sensitivity, working range, and interassay precision, but much greater signal change and calibration stability than the nonenhanced assay. In addition, with latex particles, less antiserum is needed. Coupling antibodies to latex particles offers considerable advantages, even when an improved assay detection limit is not required.

Diagnostic limitations of region-specific parathyroid hormone assays in the investigation of hypercalcaemia

Assays for N-terminus, C-terminus and mid-molecule parathyroid hormone have been assessed with respect to their sensitivity and specificity in the diagnosis of primary hyperparathyroidism (1 degree HPT). The mid-molecule assay was the most sensitive method studied and only failed to identify one out of 30 patients with histologically proven 1 degree HPT. In all three assays there was some degree of overlap between results observed in 1 degree HPT and in patients with non-parathyroid hypercalcaemia, with results in the latter group sometimes falling well within the hyperparathyroid range. This study highlights the limitations of currently available methods and emphasises the need for caution in the interpretation of parathyroid hormone (PTH) measurements.