Homozygous and compound heterozygous mutations in the ATP6V1B1 gene in patients with renal tubular acidosis and sensorineural hearing loss.

Distal renal tubular acidosis (dRTA) is characterized by the inability to excrete acid in the renal collecting ducts resulting in inappropriately alkaline urine and hyperchloremic (normal anion gap) metabolic acidosis in the context of a normal (or near-normal) glomerular filtration rate. Inborn dRTA can be due to autosomal dominant or recessive gene defects. Clinical symptoms vary from mild acidosis, incidental detection of kidney stones or renal tract calcification to severe findings such as failure to thrive, severe metabolic acidosis, and nephrocalcinosis. The majority of patients with recessive dRTA present with sensorineural hearing loss (SNHL). Few cases with abnormal widening of the vestibular aqueduct have been described with dRTA. Mutations in three different genes have been identified, namely SLC4A1, ATP6V1B1, and ATP6V0A4. Patients with mutations in the ATP6V1B1 proton pump subunit develop dRTA and in most of the cases sensorineural hearing loss early in childhood. We present two patients from two different and non-consanguineous families with dRTA and SNHL. Direct sequencing of the ATP6V1B1 gene revealed that one patient harbors two homozygous mutations and the other one is a compound heterozygous. To our knowledge, this is the first case in the literature describing homozygosity in the same dRTA gene on both alleles.

The mTOR inhibitor rapamycin significantly improves facial angiofibroma lesions in a patient with tuberous sclerosis.

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder with an incidence of approximately one in 6000. It arises from a genetic abnormality involving either the TSC1 gene on chromosome 9 or the TSC2 gene on chromosome 16. The protein product of TSC1 is hamartin and that of TSC2 is tuberin. In cells, hamartin and tuberin form a complex which inhibits the mammalian target of rapamycin (mTOR), a central controller of cell growth and proliferation. Angiofibroma affects 70-80% of patients with TSC, typically on the face. We report a patient with TSC with recurrent life-threatening haemorrhage from both kidneys due to extensive angiomyolipoma formation leading to bilateral nephrectomy and renal transplantation. Immunosuppressive treatment with rapamycin, a specific mTOR inhibitor, initiated because of renal transplantation, reduced facial angiofibroma dramatically.

Requirement of RNA and protein synthesis and inhibition by ethylenediaminetetraacetic acid of retinoic acid-induced proteoglycan release in a transplantable rat chondrosarcoma.

In in vitro cultures of prepared pieces of transplantable chondrosarcoma from F344 rats, retinoic acid enhanced the release of proteoglycan, with a lag between 6 and 14 hours. The retinoic acid-induced release of proteoglycan was inhibited in vivo and in vitro by cycloheximide, an inhibitor of protein synthesis, and in vitro by actinomycin D and cordycepin, inhibitors of RNA synthesis. These results suggested that the retinoic acid-induced release of proteoglycan depends on de novo RNA and protein synthesis. The proteoglycan release induced by retinoic acid in vitro was blocked by EDTA but not by other proteinase inhibitors (pepstatin, phenylmethylsulfonyl fluoride, and Trasylol) and was completely restored by Zn2+. The degradation of proteoglycan induced by retinoic acid may depend on newly synthesized metal-dependent proteinases.

Binding by thyroid hormones by nuclei of cells from bullfrog tadpole tail fins.

The regression of the tadpole tail is under the direct control of the thyroid hormones and offers a unique system for the study of the action of these hormones. We have examined the binding of L-triiodothyronine (T3) and L-thyroxine (T4) in vitro using tail fin bricks which included epidermal and connective cells. The binding of 125I-labeled hormones was followed in both nuclear and extranuclear fractions. High affinity and limited capacity sites for T3 and T4 were observed only for the nuclear fraction. Scatchard plots gave similar apparent dissociation constants for both hormones, about 10(-10)M. The maximum number of binding sites per nucleus for T3 was about 1500 and for T4 about 800. There was no significant change in the chemical identity of [125I]T3 and [125I]T4 which was associated with binding in the nuclei. Nuclear binding of [125I]T4 was inhibited competitively for both unlabeled T3 and T4, but unlabeled T3 displaced [125I]T3 significantly more than unlabeled T4. Thus, both binding and competition data support the conclusion that tadpole tail nuclei had more T3 than T4 binding sites.

Binding of thyroxine and triiodothyronine by nuclei of isolated tadpole liver cells.

The binding of L-triiodothyronine (T3) and L-thyroxine (T4) to cytoplasm and nuclei has been studied in isolated Rana catesbeiana tadpole liver cells. Nuclear binding for both thyroid hormones occurred more slowly at 4 C than at 25 C, but reached the same level as at 25 S. Scatchard analyses suggest high affinity, saturable binding sites for both hormones in the nuclear but not in the cytoplasmic fraction. Apparent equilibrium dissociation constants were 6.8 X 10(-10)M and 4.6 X 10(-10)M for T3 and T4, respectively. The maximum number of binding sites per nucleus for T3 was about 12,300 and for T4 about 2,300. Unlabeled T3 competed for the binding of [125I]T3 to nuclei more effectively than unlabeled T4. No difference in the competition of [125I]T4 binding with non-radioactive T3 or T4 was found. Chromatographic analysis of the bound nuclear radioactivity demonstrated no chemical modification for either hormone.

Preferential binding of tri-substituted thyronine analogs by bullfrog tadpole tail fin cytosol.

The relative strength of binding of several triiodothyronine (T3) analogs by cytosol prepared from the tail fin of the bullfrog tadpole has been tested and compared with their thyromimetic activity in tail tissue. In competitive binding experiments, four tri-substituted analogs were bound much more strongly than two tetra-derivatives. Correlation between binding and relative thyromimetic activity was observed only for three triiodo-substituted compounds, triiodothyronine, its methylene bridge analog and the acetic acid analog. The affinity for T3 was 250 times that of T4, making it unlikely that the T3 binding sites in tadpole tail fin cytosol bind T4 under physiological conditions. The difference in binding by tadpole tail fin cytosol constitutes one of the largest differences observed between T3 and T4 in a potentially significant biological system.

Scintigraphic detection of hemobilia complicating angiodysplasia.

A 78-yr-old man underwent 99mTc-labeled red cell examination for a gastrointestinal bleeding episode. Gallbladder visualization was noted during the examination. Hemobilia has been reported in a variety of pathologic conditions; scintigraphic gallbladder visualization has also been reported as a result of the unusual radiolabeling characteristics of 99mTc during red cell scintigraphy. Postmortem examination revealed angiodysplasia of the gallbladder and other sites in the gastrointestinal tract. Angiodysplasia must be considered in the pathologic spectrum of causes of hemobilia.

Fingertip temperature as an indicator for sympathetic responses.

Changes of acral skin blood flow are a commonly used indicator for sympathetic reflex responses to various stimuli. The goal of the present study was to determine whether decreases in fingertip temperature are indicative for sympathetic induced changes in microcirculation. Infrared thermography demonstrated that various stimuli triggering the sympathetic nervous system induced decreases in cutaneous microcirculation, most prominently in fingertip skin. Various such stimuli induced almost immediate temporary vasoconstriction, measured by laser Doppler flux and photoplethysmography. With a lag phase of approximately 15 s, reduced microcirculation was also reflected by a transient decrease in fingertip temperature. Vasoconstrictions were easily demonstrable by fingertip temperature when the starting fingertip temperature was above 32 degrees C and vasoconstriction lasted at least 5 s. Temperature measurement offers the advantages of ease and simplicity of performance and analysis, compared with the more complex analyses of flux and pulse volume.

Superior vena cava obstruction in fibrosing mediastinitis: demonstration of right-to-left shunt and venous collaterals.

Multiple venous collateral pathways have been described in patients with superior vena cava obstruction. Systemic venous-to-pulmonary venous communication is the most unusual, having been described in a few cases of thoracic malignancy. In a patient with fibrosing mediastinitis radionuclide venography with 99Tcm-macroaggregated albumin demonstrated a systemic venous-pulmonary venous right-to-left shunt in addition to systemic and portal venous collaterals. It is apparent that systemic venous-to-pulmonary venous anastomoses may occur in the absence of malignant disease.

Isolation and identification of a major urinary canthaxanthin metabolite in rats.

The urinary metabolic pattern after administration of the radiolabeled non-provitamin A carotenoid canthaxanthin was investigated in rats. In the rather complex HPLC urinary metabolic pattern a fraction was found which was conjugated. Deconjugation of the polar conjugates with glusulase, purification of the metabolite with HPLC and identification with GC-MS and NMR revealed that it was 3-hydroxy-4-oxo-7,8-dihydro-beta-ionone. This structure was confirmed by comparisons with HPLC retention times, UV/VIS- and NMR-spectroscopy and GC-MS of the synthesized compound.

A probe holder for precise intranasal microcirculation measurements.

A probe holder for long-term measurements of intranasal microcirculation by laser Doppler flowmetry is described. It is adjustable to any physiognomy and allows precise intranasal probe insertion. It is based on a commercially-available shooting-spectacles frame and might also be useful for other measurements such as intranasal temperature, humidity and pO2.

Morphine-augmented cholescintigraphy in acute cholecystitis. A satisfactory alternative to delayed imaging.

The utility of morphine-augmented cholescintigraphy was reviewed in 32 patients with suspected acute cholecystitis. All patients were administered 2 mg morphine sulfate intravenously when the gallbladder failed to visualize 30 minutes into the study, and imaging continued for up to 60 minutes. Sensitivity for detection of acute cholecystitis was 93% (13 out of 14). Specificity was 78% (14 out of 18). Three of four false-positives occurred in the setting of prolonged fasting and chronic cholecystitis. Cumulative experience suggests that the technique is diagnostically equivalent to imaging for up to 4 hours and that specificity remains incomplete in the setting of prolonged fasting, chronic cholecystitis and other conditions known to affect conventional cholescintigraphy.

Axillary iodine-131 accumulation due to perspiration.

A case of spurious axillary uptake of I-131 proven to be caused by perspiration is presented. False-positive localizations of radioiodine, both pathologic and physiologic, are reviewed to avoid confusion of these entities with functioning thyroid carcinoma metastases.

Impact of mammalian target of rapamycin inhibition on autosomal-dominant polycystic kidney disease.

Autosomal-dominant polycystic kidney disease (ADPKD) is characterized by the progressive development of countless cysts in both kidneys, which compress the cyst-free renal parenchyma, leading to a loss of renal function and the need for renal replacement therapy and/or kidney transplantation in ∼50% of affected patients. In animal models of experimental polycystic kidney disease, the mammalian target of rapamycin (mTOR) inhibitors sirolimus and everolimus effectively reduce cyst growth and loss of renal function. Furthermore, an analysis of renal transplant patients with ADPKD has shown that cystic kidney and liver volumes regress more on a sirolimus-based regimen than on a calcineurin inhibitor-based immunosuppressive regimen. Several prospective controlled clinical trials have been initiated to investigate whether mTOR inhibitors retard cyst growth and slow renal functional deterioration in patients with ADPKD. Study results are expected in 2010.