Identification of low density lipoprotein receptor-related protein-2/megalin as an endocytic receptor for seminal vesicle secretory protein II

The low density lipoprotein receptor-related protein-2/megalin (LRP-2) is an endocytic receptor that is expressed on the apical surfaces of epithelial cells lining specific regions of the male and female reproductive tracts. In the present study, immunohistochemical staining revealed that LRP-2 is also expressed by epithelial cells lining the ductal region and the ampulla of the rat seminal vesicle. To identify LRP-2 ligands in the seminal vesicle, we probed seminal vesicle fluid with 125I-labeled LRP-2 in a gel-blot overlay assay. A 100-kDa protein (under non-reducing conditions) was found to bind the radiolabeled receptor. The protein was isolated and subjected to protease digestion, and the proteolytic fragments were subjected to mass spectroscopic sequence analysis. As a result, the 100-kDa protein was identified as the seminal vesicle secretory protein II (SVS-II), a major constituent of the seminal coagulum. Using purified preparations of SVS-II and LRP-2, solid-phase binding assays were used to show that the SVS-II bound to the receptor with high affinity (Kd = 5.6 nM). The binding of SVS-II to LRP-2 was inhibited using a known antagonist of LRP-2 function, the 39-kDa receptor-associated protein RAP. Using a series of recombinant subfragments of SVS-II, the LRP-2 binding site was mapped to a stretch of repeated 13-residue modules located in the central portion of the SVS-II polypeptide. To evaluate the ability of LRP-2 to mediate 125I-SVS-II endocytosis and lysosomal degradation, ligand clearance assays were performed using differentiated mouse F9 cells, which express high levels of LRP-2. Radiolabeled SVS-II was internalized and degraded by the cells, and both processes were inhibited by antibodies to LRP-2 or by RAP. The results indicate that LRP-2 binds SVS-II and can mediate its endocytosis leading to lysosomal degradation.

Impact evaluation of iron & iodine fortified salt

As a novel approach to tackle the problems of iron deficiency anaemia and iodine deficiency disorders (IDDs), which often coexist, the National Institute of Nutrition has developed iron and iodine fortified common salt (double fortified salt-DFS) as a public health measure. This salt has undergone a battery of laboratory and field tests to evaluate its feasibility for use in a national programme. The DFS is designed to provide 1 mg of iron and 15 micrograms of iodine per gram of common salt. This was made possible by the inclusion of a polyphosphate stabilizer, sodium hexametaphosphate (SHMP) at 1 per cent level. The stability of iron and iodine was found to be good up to 6 months. However, the stability of iodine depended upon the quality of the salt used for fortification. The biological effects of long-term consumption of DFS were evaluated in experimental rats and in field trials. Both iron and iodine from the salt were found to be biologically available in regenerating haemoglobin and in increasing excretion of iodine in urine. When this salt was tested in tribal villages endemic for goitre and iron deficiency anaemia, the bioresponse was good with regard to the iodine status but was not uniform in all segments with regard to iron, probably due to confounding variables. In a study carried out in residential school children where such variables did not exist, DFS was found to have significant impact on haemoglobin status in anaemic children and improved their urinary iodine excretion. The consumption of DFS for 2 yr did not have any adverse effects in school children as well as in the tribal population. Parameters related to calcium homeostasis were not altered in children receiving DFS. Histopathological examination of tissues and radiological examination of bone did not reveal any abnormality in DFS fed rats. Similarly serum and urinary parameters related to calcium and phosphorus were not altered in DFS fed rats. Therefore, DFS is presented as a feasible and effective strategy to control the double deficiency of iron and iodine in our community.

Thiazolidinediones inhibit lipoprotein lipase activity in adipocytes

The thiazolidinediones troglitazone and BRL 49653 improve insulin sensitivity in humans and animals with insulin resistance. Adipose tissue lipoprotein lipase is an insulin-sensitive enzyme. We examined the effects of thiazolidinediones on lipoprotein lipase expression in adipocytes. When added to 3T3-F442A, 3T3-L1, and rat adipocytes in culture, troglitazone and BRL 49653 inhibited lipoprotein lipase activity. This inhibition was observed at concentrations as low as 0.1 microM and within 2 h after addition of the drug. Lipoprotein lipase activity was inhibited in differentiated adipocytes as well as the differentiating cells. Despite this decrease in enzyme activity, these drugs increased mRNA levels in undifferentiated 3T3-F442A and 3T3-L1 cells and had no effect on mRNA expression or synthesis of lipoprotein lipase in differentiated cells. Western blot analysis showed that these drugs did not affect the mass of the enzyme protein. Lipoprotein lipase activity in cultured Chinese hamster ovary cells was not inhibited by troglitazone. Glucose transport, biosynthesis of lipids from glucose or the biosynthesis of proteins were unaffected by thiazolidinediones in differentiated cells, whereas glucose transport and lipid biosynthesis were increased when these drugs were added during differentiation. These results show that troglitazone and BRL 49653 have a specific, post-translational inhibitory effect on lipoprotein lipase in adipocytes, yet they promote lipid accumulation and differentiation in preadipocytes.

A survey of dermatophytosis in animals in Madras, India

Two hundred and eleven dogs (including strictly house and stray dogs) and 170 cattle in and around the city of Madras, India were screened for the presence of dermatophytosis. 106 strains of dermatophytes (89 strains from dogs and 17 strains from bovines) were isolated. 57/106 strains were Trichophyton mentagrophytes var. mentagrophytes and 42/106 strains were of the Microsporum gypseum complex. 5 strains of T. rubrum and 2 strains of T. simii were also obtained in culture. A predominance of M. gypseum complex isolates was recorded in stray dogs and cattle and T. mentagrophytes var. mentagrophytes and T. rubrum in strictly house dogs. The family history of the owners of the most of the dogs had clear records of dermatophytosis. Further, the owners of the 11 dogs that yielded T. mentagrophytes var. mentagrophytes had either tinea corporis or tinea pedis. The etiological agent of all the 11 human cases was T. mentagrophytes var. interdigitale. Similarly the owners of 4 of the 5 dogs that yielded T. rubrum were known T. rubrum patients. All these patients responded to oral griseofulvin or ketaconozole, but the recurrence of lesions was noted with the cessation of treatment. None of the patients had onychomycosis and the family history of all the patients revealed no reports of T. rubrum infections. The pet dogs were presumed to be the source of re-infection. Reversed transmission of dermatophytes from humans to animals may be the reason for the selective predominance of these organisms in strictly house dogs. They also may act as sources of reinfection. Most of the animals had small, occult, scattered lesions. These lesions may either go unnoticed or are ignored by the owners of the animals. The taxonomic status of T. mentagrophytes and T. mentagrophytes var. interdigitale was aligned to their teleomorph Arthroderma vanbreuseghemii. Our study suggests that the periodic screening and medication of all live-stock are essential for the prevention and management of the public health problem caused by dermatophytes.

Lack of effect of leptin on glucose transport, lipoprotein lipase, and insulin action in adipose and muscle cells

The effect of leptin on glucose transport, lipogenesis, and lipoprotein lipase activity was studied in cultured rat adipocytes and 3T3-L1 adipocytes. Leptin had no effect on basal and insulin stimulated glucose transport in isolated adipocytes from the rat and the genetically obese mouse. The incorporation of glucose into lipids was also unaffected. Lipoprotein lipase (LPL) activity remained unchanged in response to leptin in these cells, as well as in minced adipose tissue. Leptin also had no effect on both basal and insulin-stimulated glucose transport in cultured rat and human skeletal muscle cells. These studies showed that leptin had no effect on glucose transport, lipoprotein lipase activity, and insulin action in fat and muscle cells in vitro.

Adipose tissue ob mRNA expression in humans: discordance with plasma leptin and relationship with adipose TNFalpha expression

Elevated plasma leptin levels are found in obese humans, suggesting a defect in the function of leptin in regulating body weight and adiposity. In 53 subjects covering a broad range of adiposity, we examined the relationships between plasma leptin, adipose tissue ob mRNA levels, and adipose tissue TNF mRNA. There was a highly significant correlation between plasma leptin levels and every index of adiposity. In contrast, the relationship between ob mRNA levels and adiposity was weak. Adipose tissue from obese subjects demonstrated higher ob mRNA levels than adipose tissue from lean subjects (lean: 0.49+/-0.05; obese 0.87+/-0.09 arbitrary units, P< 0.05). However, there was no significant correlation between body fat and ob mRNA level. In addition, there was no significant relationship between ob mRNA levels and plasma leptin levels, which were measured in the same subjects. In addition to the measure of ob mRNA levels, adipose TNF mRNA levels were measured in 18 subjects. TNF mRNA levels varied with ob mRNA levels (r = 0.44, P = 0.06). These data show that plasma leptin levels are not directly related to adipose tissue ob mRNA levels, suggesting posttranscriptional regulation of leptin expression, either at the level of the adipocyte, or by alteration of plasma leptin degradation or clearance. In addition, the parallel changes in ob and TNF mRNA in adipose tissue suggest that these two important factors in the defense against obesity may be regulated similarly.

Altered beta-tubulin isotype expression in paclitaxel-resistant human prostate carcinoma cells

To investigate the role of beta-tubulin isotype composition in resistance to paclitaxel, an anti-microtubule agent, human prostate carcinoma (DU-145) cells were intermittently exposed to increasing concentrations of paclitaxel. Cells that were selected and maintained at 10 nM paclitaxel (Pac-10) were fivefold resistant to the drug. Pac-10 cells accumulated radiolabelled paclitaxel to the same extent as DU-145 cells and were negative for MDR-1. Analysis of Pac-10 and DU-145 cells by flow cytometry showed similar cell cycle patterns. Immunofluorescent staining revealed an overall increase of alpha- and beta-tubulin levels in Pac-10 cells compared with DU-145 cells. Examination of beta-tubulin isotype composition revealed a significant increase in betaIII isotype in the resistant cells, both by immunofluorescence and by western blot analysis. Reverse transcription-polymerase chain reaction (RT-PCR) analysis of the isotypes confirmed the increase observed for the betaIII by exhibiting ninefold higher betaIII mRNA levels and also showed fivefold increase of the betaIVa transcript. In addition, analysis of paclitaxel-resistant cells that were selected at increasing levels of the drug (Pac 2, 4, 6, 8 and 10) exhibited a positive correlation between increasing betaIII levels and increasing resistance to paclitaxel. Increased expression of specific beta-tubulin isotypes and subsequent incorporation into microtubules may alter cellular microtubule dynamics, providing a defence against the anti-microtubule effects of paclitaxel and other tubulin-binding drugs.

Cloning and sequencing of human betaIII-tubulin cDNA: induction of betaIII isotype in human prostate carcinoma cells by acute exposure to antimicrotubule agents

Antimicrotubule drugs are used as chemotherapeutic agents due to their effects on essential cellular functions such as mitosis, organelle transport and maintenance of cell shape. When used in combination, paclitaxel with estramustine or vinblastine has demonstrated activity against hormone refractory prostate cancer. To understand the mechanism of resistance that develops in patients as a result of antimicrotubule drug therapy, we exposed human prostate carcinoma cells to IC20 and IC40 doses of estramustine, paclitaxel or vinblastine for 48 h and examined the beta-tubulin (the cellular target) isotype composition. The results revealed an increase in the betaIII-tubulin isotype as a result of drug treatment both at protein and message levels. In addition, examination of human brain cell lines with different intrinsic levels of betaIII showed that cell lines with higher betaIII levels were more resistant to paclitaxel. These results are in agreement with our previous findings in human prostate carcinoma cell lines that were made resistant to estramustine or paclitaxel and suggest an important function for betaIII in antimicrotubule drug resistance. Also, the complete coding sequence of human betaIII tubulin reported here will provide molecular tools for future investigations.

Soil dermatophytes in Madras, India, in relation to human ringworm

A total of 269 soil samples collected from different habitats in Madras, India, were screened for the presence of dermatophytes by the hair-baiting technique. Three strains of Trichophyton mentagrophytes and 16 strains of Microsporum gypseum complex were isolated. These strains were subjected to the mating experiment. 2/3 soil isolates of Trichophyton mentagrophytes belonged to Arthroderma vanbreuseghemii (+) mating type, and 1/3 was Arthroderma vanbreuseghemii (-) mating type. Similarly 6/70 clinical strains of Trichophyton mentagrophytes isolated in our previous study also belonged to Arthroderma vanbreuseghemii (+) mating type. These 6 strains were isolated from severe cases of tinea capitis in children belonging to rural Madras. The teleomorphic and mating type homology between the clinical and soil isolates of T. mentagrophytes suggest that soil may act as reservoir for these organisms. The incompatible clinical strains of T. mentagrophytes var. interdigitale and A. vanbreuseghemii showed DNA homology, thereby establishing the epidemiologic link which supports the above findings.

Isolation of Microsporum nanum from a patient with tinea corporis in Madras, India

Microsporum nanum was isolated from a case of tinea corporis in a 16-year-old boy. This is the first recorded case of human ringworm infection caused by M. nanum in India.

Interaction of apolipoprotein J-amyloid beta-peptide complex with low density lipoprotein receptor-related protein-2/megalin. A mechanism to prevent pathological accumulation of amyloid beta-peptide

Apolipoprotein J (apoJ) has been shown to be the predominant amyloid beta-peptide (Abeta)-binding protein in cerebrospinal fluid. We have previously demonstrated that the endocytic receptor low density lipoprotein receptor-related protein-2/megalin (LRP-2), which is expressed by choroid plexus epithelium and ependymal cells lining the brain ventricles and neural tube, binds and mediates cellular uptake of apoJ (Kounnas, M. Z., Loukinova, E. B., Stefansson, S., Harmony, J. A., Brewer, B., Strickland, D. K., and Argraves, W. S. (1995) J. Biol. Chem. 270, 13070-13075). In the present study, we evaluated the ability of apoJ to mediate binding of Abeta1-40-apoJ complex to LRP-2 in vitro. Immunoblot analysis showed that incubation of apoJ with Abeta1-40 resulted in the formation of Abeta1-40-apoJ complex and the inhibition of the formation of Abeta1-40 aggregates. Using an enzyme-linked immunosorbent assay, an estimated dissociation constant (Kd) of 4.8 nM was derived for the interaction between Abeta1-40 and apoJ. Enzyme-linked immunosorbent assay was also used to study the interaction of the Abeta1-40-apoJ complex with LRP-2. The results showed that Abeta alone did not bind directly to LRP-2; however, when Abeta1-40 was combined with apoJ to form a complex, binding to LRP-2 took place. The binding interaction could be blocked by inclusion of the receptor-associated protein, an antagonist of apoJ binding to LRP-2. When LRP-2-expressing cells were given 125I-Abeta1-40, cellular uptake of the radiolabeled peptide was promoted by co-incubation with apoJ. When the cells were provided purified 125I-Abeta1-40-apoJ complex, the complex was internalized and degraded, and both processes were inhibited with polyclonal LRP-2 antibodies. Furthermore, chloroquine treatment inhibited the cellular degradation of the complex. The data indicate that apoJ facilitates Abeta1-40 binding to LRP-2 and that the receptor mediates cellular clearance of Abeta1-40-apoJ complex leading to lysosomal degradation of Abeta1-40. The findings support the possibility that LRP-2 can act in vivo to mediate clearance of the complex from biological fluids such as cerebrospinal fluid and thereby play a role in the regulation of Abeta accumulation.

Scatter factor/hepatocyte growth factor expression enhances human glioblastoma tumorigenicity and growth

We have shown previously that the multifunctional cytokine scatter factor/hepatocyte growth factor (SF/HGF) is elevated in human malignant gliomas. In this study we investigated how human SF/HGF expression affects the malignancy of the U373 human glioblastoma cell line in vivo and in vitro. Human SF/HGF gene transfer increased U373 glioblastoma tumorigenicity by > or = 20-fold and enhanced the growth rate of intracerebral U373 xenografts by 3- to 8-fold. SF/HGF expression had no effect on the proliferation of glioblastoma cell monolayers but increased their anchorage-independent colony formation in soft agar by 5- to 8-fold. These results are the first to show that SF/HGF expression by human glioblastoma cells enhances their growth dysregulation in vitro and malignancy in vivo.

Dry mixing technique for the large scale production of iodine fortified salt in India

Dry mixing technique was used successfully in three factories in India for the manufacture of iodine fortified salt. Permitted food additives, calcium carbonate and magnesium carbonate, were used with potassium iodate. The technology was smooth and free from any problem. Since the formerly conventional, but now superceded on analytical performance criteria, spray-mixing system was not used in the study, plants of the economics either batch mixing or continuous processes were more in evidence, and could be compared with avoidable spray mixing production performance data. The iodine fortified salt was free-flowing and retained the colour of the common salt. The iodine distribution was uniform (about 30 ppm). Long distance road transportation did not affect the iodine stability and its consistency. Storage studies showed satisfactory stability and the fortified salt had prolonged shelf-life beyond one year.

Predicted structure of the extracellular region of ligand-gated ion-channel receptors shows SH2-like and SH3-like domains forming the ligand-binding site

Fast synaptic neurotransmission is mediated by ligand-gated ion-channel (LGIC) receptors, which include receptors for acetylcholine, serotonin, GABA, glycine, and glutamate. LGICs are pentamers with extracellular ligand-binding domains and form integral membrane ion channels that are selective for cations (acetylcholine and serotonin 5HT3 receptors) or anions (GABAA and glycine receptors and the invertebrate glutamate-binding chloride channel). They form a protein superfamily with no sequence similarity to any protein of known structure. Using a 1D-3D structure mapping approach, we have modeled the extracellular ligand-binding domain based on a significant match with the SH2 and SH3 domains of the biotin repressor structure. Refinement of the model based on knowledge of the large family of SH2 and SH3 structures, sequence alignments, and use of structure templates for loop building, allows the prediction of both monomer and pentamer models. These are consistent with medium-resolution electron microscopy structures and with experimental structure/function data from ligand-binding, antibody-binding, mutagenesis, protein-labeling and subunit-linking studies, and glycosylation sites. Also, the predicted polarity of the channel pore calculated from electrostatic potential maps of pentamer models of superfamily members is consistent with known ion selectivities. Using the glycine receptor alpha 1 subunit, which forms homopentamers, the monomeric and pentameric models define the agonist and antagonist (strychnine) binding sites to a deep crevice formed by an extended loop, which includes the invariant disulfide bridge, between the SH2 and SH3 domains. A detailed binding site for strychnine is reported that is in strong agreement with known structure/function data. A site for interaction of the extracellular ligand-binding domain with the activation of the M2 transmembrane helix is also suggested.

Immunohistochemical analysis of beta-tubulin isotypes in human prostate carcinoma and benign prostatic hypertrophy

BACKGROUND

beta-tubulin, the intracellular target of several antimicrotubule agents, is encoded by at least six genes and exists as multiple isotypes with tissue-specific expression. Previous in vitro studies indicated that tubulin isotype composition may affect polymerization properties, dynamics, and sensitivity to drugs.

METHODS

To investigate the isotype composition of beta-tubulin in human prostate, tissues were collected from 26 patients after radical prostatectomy and sections were stained with isotype-specific antibodies.

RESULTS

beta IV tubulin is the predominant isotype in benign prostatic hyperplasia (BPH) and adenocarcinoma, showing significantly stronger immunohistochemical expression than beta II and beta III, particularly in Gleason's grade 3 and 4 cancers. Staining for the beta II isotype was invariably weak and often absent in BPH and normal glands. There was a marked increase in beta II isotype stain from BPH to cancer in 77% of the patients, suggesting that the expression of this isotype is related to malignant status.

CONCLUSIONS

The beta II tubulin isotype is a potential marker for prostate adenocarcinoma. The possibility that tumor beta-tubulin isotype composition may effect the response to antimicrotubule drug therapy in prostate cancer and other tumors merit investigation.

Interaction of estramustine with tubulin isotypes

The interaction of the antimitotic agent estramustine with bovine microtubule proteins and purified tubulin was investigated. Direct photoaffinity labeling of microtubule protein with [14C]estramustine resulted in the labeling of both alpha- and beta-tubulin, and this was inhibited with unlabeled estramustine in a dose-dependent manner. [14C]Estramustine was incorporated into both the soluble and polymerized forms of tubulin. The affinity constant for estramustine binding to tubulin was determined by equilibrium dialysis to be 23 +/- 5 mM. Estramustine did not affect [3H]vinblastine binding, and vinblastine had no effect on direct labeling with [14C]estramustine. Both rhizoxin and paclitaxel decreased the covalent labeling of tubulin with [14C]estramustine in a dose-dependent fashion and were noncompetitive inhibitors of the binding of estramustine to tubulin. The binding of colchicine to tubulin was not inhibited by estramustine as detected by fluorescence and DEAE filter assays. The estramustine binding site on tubulin is therefore distinct from that of colchicine and vinblastine and may at least partially overlap with the binding site for paclitaxel. In both bovine brain microtubules and cytoskeletal proteins from human prostatic carcinoma cells, the incorporation of [14C]estramustine into the beta III isotype of tubulin was found to occur with a reduced efficiency compared to that of the other beta-tubulin isotypes and alpha-tubulin. Since this isotype is overexpressed in estramustine resistant human prostate carcinoma cells, these results indicate that beta III-tubulin may play a role in the response to the effects of estramustine.

ABO blood groups in relation to the infection rate of dermatophytosis

The role of ABO blood groups in the carriage rate of dermatophytosis was studied. Blood grouping was done for 108 culture-proven dermatophytosis patients. Forty-nine patients belonged to blood group A, 54 to blood group O, three to blood group B and two to blood group AB. The incidence of dermatophytosis was found to be high in patients of blood group O and A. However, chronicity of the disease was more frequent in those in blood group A. The control group consisted of 100 healthy subjects. Sixteen out of 29 control subjects belonging to blood group A had a history of skin infections. None of the O blood group control subjects had a history of skin infections. Our study suggests that A blood group subjects may be prone to chronic dermatophytosis.

Effect of tumor necrosis factor-alpha on basal and insulin-stimulated glucose transport in cultured muscle and fat cells

It has been reported that tumor necrosis factor-alpha (TNF-alpha) inhibits insulin action in adipocytes and plays an important role as mediator of insulin resistance in non-insulin-dependent diabetes. The effect of this cytokine on insulin action in muscle, which is responsible for 80% of the glucose disposal in the body, has not been studied. Therefore, we examined the effect of TNF-alpha on basal and insulin-mediated transport of 2-deoxy[3H]-glucose in L6 rat muscle cells. TNF-alpha treatment for 5 days up to a concentration of 20 ng/mL or 8 days at 10 ng/mL did not inhibit the insulin-stimulated increase in deoxyglucose transport in L6 cells. However, there was a significant increase in basal transport in TNF-alpha- treated cells. Comparative experiments with 3T3-L1 adipocytes showed that in cells cultured with insulin, TNF-alpha decreased basal transport but the insulin-stimulated increase was unaffected. In cells cultured without insulin, basal transport was slightly increased and the insulin-stimulated increase in transport was decreased by approximately 60% but the cell protein was decreased by approximately 60%, suggesting cytotoxicity. Cells cultured without insulin were more sensitive to inhibition of 14C-alanine incorporation into proteins by low concentrations of TNF-alpha compared with cells cultured with insulin. These results suggest that TNF-alpha affects glucose metabolism, causing increased basal uptake in muscle cells and decreased uptake in adipocytes. TNF-alpha appears to affect general cell metabolism, including glucose transport in adipocytes, and not specifically insulin-stimulated glucose transport.

Renal amyloidosis--a clinicopathologic study

A total of 19,075 necropsies and 1169 renal biopsies were scrutinised over a period of 20 years (1973-1992) retrospectively with an aim to study the incidence and pattern of renal amyloidosis in Nair Hospital. A total of 75 cases with amyloidosis were detected, 33 from the necropsy series (0.162%) and 42 from biopsies (3.59%). Secondary amyloidosis was seen in 82.66% and primary amyloidosis in 10.66%. Tuberculosis of various organs was the main cause of secondary amyloidosis (79.03%). Nephrotic syndrome was the common mode of presentation (52%). Besides kidney, which were involved in all cases, the liver, spleen and adrenals were other commonly involved organs at necropsy. Renal failure was the leading cause of death (51.51%). Thioflavine-T proved to be more sensitive technique than other conventional staining methods. The potassium permanganate test is a useful test to distinguish secondary amyloid fibrils from other amyloid fibrils. Abdominal fat aspiration may prove to be specific, sensitive and a routine procedure enabling the early diagnosis of amyloidosis leading to increased incidence of amyloidosis during life than at necropsy.