Apoptosis is induced in leishmanial cells by a novel protein kinase inhibitor withaferin A and is facilitated by apoptotic topoisomerase I-DNA complex

Protein kinase C (PKC) is an important constituent of the signaling pathways involved in apoptosis. We report here that like staurosporine, withaferin A is a potent inhibitor of PKC. In Leishmania donovani, the inhibition of PKC by withaferin A causes depolarization of DeltaPsim and generates ROS inside cells. Loss of DeltaPsim leads to the release of cytochrome c into the cytosol and subsequently activates caspase-like proteases and oligonucleosomal DNA cleavage. Moreover, in treated cells, oxidative DNA lesions facilitate the stabilization of topoisomerase I-mediated cleavable complexes, which also contribute to DNA fragmentation. However, withaferin A and staurosporine cannot induce cleavable complex formation in vitro with recombinant topoisomerase I nor with nuclear extracts from control cells. Taken together, our results indicate that inhibition of PKC by withaferin A is a central event for the induction of apoptosis and that the stabilization of topoisomerase I-DNA complex is necessary to amplify apoptotic process.

SMAD4 mutations found in unselected HHT patients

BACKGROUND

Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant disease exhibiting multifocal vascular telangiectases and arteriovenous malformations. The majority of cases are caused by mutations in either the endoglin (ENG) or activin receptor-like kinase 1 (ALK1, ACVRL1) genes; both members of the transforming growth factor (TGF)-beta pathway. Mutations in SMAD4, another TGF-beta pathway member, are seen in patients with the combined syndrome of juvenile polyposis (JP) and HHT (JP-HHT).

METHODS

We sought to determine if HHT patients without any apparent history of JP, who were undergoing routine diagnostic testing, would have mutations in SMAD4. We tested 30 unrelated HHT patients, all of whom had been referred for DNA based testing for HHT and were found to be negative for mutations in ENG and ALK1.

RESULTS

Three of these people harboured mutations in SMAD4, a rate of 10% (3/30). The SMAD4 mutations were similar to those found in other patients with the JP-HHT syndrome.

CONCLUSIONS

The identification of SMAD4 mutations in HHT patients without prior diagnosis of JP has significant and immediate clinical implications, as these people are likely to be at risk of having JP-HHT with the associated increased risk of gastrointestinal cancer. We propose that routine DNA based testing for HHT should include SMAD4 for samples in which mutations in neither ENG nor ALK1 are identified. HHT patients with SMAD4 mutations should be screened for colonic and gastric polyps associated with JP.

Performance of a static-anode/flat-panel x-ray fluoroscopy system in a diagnostic strength magnetic field: A truly hybrid x-ray/MR imaging system

Minimally invasive procedures are increasing in variety and frequency, facilitated by advances in imaging technology. Our hybrid imaging system (GE Apollo flat panel, custom Brand x-ray static anode x-ray tube, GE Lunar high-frequency power supply and 0.5 T Signa SP) provides both x-ray and MR imaging capability to guide complex procedures without requiring motion of the patient between two distant gantries. The performance of the x-ray tube in this closely integrated system was evaluated by modeling and measuring both the response of the filament to an externally applied field and the behavior of the electron beam for field strengths and geometries of interest. The performance of the detector was assessed by measuring the slanted-edge modulation transfer function (MTF) and when placed at zero field and at 0.5 T. Measured resonant frequencies of filaments can be approximated using a modified vibrating beam model, and were at frequencies well below the 25 kHz frequency of our generator for our filament geometry. The amplitude of vibration was not sufficient to cause shorting of the filament during operation within the magnetic field. A simple model of electrons in uniform electric and magnetic fields can be used to estimate the deflection of the electron beam on the anode for the fields of interest between 0.2 and 0.5 T. The MTF measured at the detector and the DQE showed no significant difference inside and outside of the magnetic field. With the proper modifications, an x-ray system can be fully integrated with a MR system, with minimal loss of image quality. Any x-ray tube can be assessed for compatibility when placed at a particular location within the field using the models. We have also concluded that a-Si electronics are robust against magnetic fields. Detailed knowledge of the x-ray system installation is required to provide estimates of system operation.

Photoluminescence and raman study of CdS-Al2O3 nanocomposite films prepared by sol-gel techniques

The optical and microstructural properties of CdS-Al2O3 nanocomposite (CdS-Al2O3 = 20:80 to 50:50) thin films synthesized by sol-gel techniques were studied. Optical transmission spectra indicated a marked blue shift of the absorption edge due to quantum confinement. Band gaps of CdS-Al2O3 nanocomposites were found to vary in the range 3.69-2.61 eV. The sizes of the nanocrystals, estimated from the blue shift (0.2-1.2 eV) of the absorption edges and transmission electron microscopy, were found to vary in the range 2.8-7.0 nm. X-ray diffraction studies showed reflections from (111), (200), (220), and (311) planes of CdS in the cubic phase. Microstructural characterization by high-resolution transmission electron microscope (HRTEM) indicated well crystallinity of the nanoparticles and lattice fringes supported the cubic phase of CdS. Raman spectroscopy was carried out for CdS-Al2O3 nanocomposites, which indicated a prominent peak at approximately 299 cm(-1). Significant changes in the peak position and intensity of the Raman peak were observed with varying the annealing temperature (373-573 K). Photoluminescence measurements indicated a prominent broad peak at approximately 1.81 eV due to the surface defects in the CdS nanocrystallites. The present study revealed Al2O3 to be a good capping material for CdS nanoparticles.

Camptothecin induced mitochondrial dysfunction leading to programmed cell death in unicellular hemoflagellate Leishmania donovani

The parasites of the order kinetoplastidae including Leishmania spp. emerge from most ancient phylogenic branches of unicellular eukaryotic lineages. In their life cycle, topoisomerase I plays a significant role in carrying out vital cellular processes. Camptothecin (CPT), an inhibitor of DNA topoisomerase I, induces programmed cell death (PCD) both in the amastigotes and promastigotes form of L. donovani parasites. CPT-induced cellular dysfunction in L. donovani promastigotes is characterized by several cytoplasmic and nuclear features of apoptosis. CPT inhibits cellular respiration that results in mitochondrial hyperpolarization taking place by oligomycin-sensitive F0-F1 ATPase-like protein in leishmanial cells. During the early phase of activation, there is an increase in reactive oxygen species (ROS) inside cells, which causes subsequent elevation in the level of lipid peroxidation and decrease in reducing equivalents like GSH. Endogenous ROS formation and lipid peroxidation cause eventual loss of mitochondrial membrane potential. Furthermore, cytochrome c is released into the cytosol in a manner independent of involvement of CED3/CPP32 group of proteases and unlike mammalian cells it is insensitive to cyclosporin A. These events are followed by activation of both CED3/CPP32 and ICE group of proteases in PCD of Leishmania. Taken together, our study indicates that different biochemical events leading to apoptosis in leishmanial cells provide information that could be exploited to develop newer potential therapeutic targets.

Hyperinsulinism and hyperammonemia syndrome: report of twelve unrelated patients

Hyperinsulinism and hyperammonemia syndrome has been reported as a cause of moderately severe hyperinsulinism with diffuse involvement of the pancreas. The disorder is caused by gain of function mutations in the GLUD1 gene, resulting in a decreased inhibitory effect of guanosine triphosphate on the glutamate dehydrogenase (GDH) enzyme. Twelve unrelated patients (six males, six females) with hyperinsulinism and hyperammonemia syndrome have been investigated. The phenotypes were clinically heterogeneous, with neonatal and infancy-onset hypoglycemia and variable responsiveness to medical (diazoxide) and dietary (leucine-restricted diet) treatment. Hyperammonemia (90-200 micromol/L, normal <50 micromol/L) was constant and not influenced by oral protein, by protein- and leucine-restricted diet, or by sodium benzoate or N-carbamylglutamate administration. The patients had mean basal GDH activity (18.3 +/- 0.9 nmol/min/mg protein) not different from controls (17.9 +/- 1.8 nmol/min/mg protein) in cultured lymphoblasts. The sensitivity of GDH activity to inhibition by guanosine triphosphate was reduced in all patient lymphoblast cultures (IC(50), or concentrations required for 50% inhibition of GDH activity, ranging from 140 to 580 nM, compared with control IC(50) value of 83 +/- 1.0 nmol/L). The allosteric effect of ADP was within the normal range. The activating effect of leucine on GDH activity varied among the patients, with a significant decrease of sensitivity that was correlated with the negative clinical response to a leucine-restricted diet in plasma glucose levels in four patients. Molecular studies were performed in 11 patients. Heterozygous mutations were localized in the antenna region (four patients in exon 11, two patients in exon 12) as well as in the guanosine triphosphate binding site (two patients in exon 6, two patients in exon 7) of the GLUD1 gene. No mutation has been found in one patient after sequencing the exons 5-13 of the gene.

Aberrant mRNA splicing associated with coding region mutations in children with carnitine-acylcarnitine translocase deficiency

This report describes three infants with genetic defects of carnitine-acylcarnitine translocase (CACT), an inner mitochondrial membrane carrier that is essential for long-chain fatty acid oxidation. Two of the patients were of European and Chinese origin; the third was from consanguineous Turkish parents. CACT activity was totally deficient in cultured skin fibroblasts from all three patients. Patient 1 was heterozygous for a paternal frameshift mutation (120 del T in exon 1) and a maternal lariat branch point mutation (-10 T --> G in intron 2). Patient 2 was heterozygous for the same lariat branch point (-10T --> G intron 2) mutation, derived from the father, and a maternal frameshift mutation (362 del G in exon 3). Patient 3 was homozygous for a frameshift mutation (306 del C in exon 3). All of the three frameshift mutations give rise to the same stop codon at amino acid residue 127 which is predicted to cause premature protein truncation. In addition, cDNA transcript analysis showed that these coding sequence mutations also increase the amount of aberrant mRNA splicing and exon skipping at distances up to 7.7 kb nucleotides from mutation sites. The data suggest that the stability of mRNA transcripts is decreased or the frequency of aberrant splicing is increased in the presence of CACT coding sequence mutations. These results confirm that CACT is the genetic locus of the recessive mutations responsible for the fatal defects of fatty acid metabolism previously associated with deficiency of translocase activity in these three cases.

Unilateral dopamine depletion increases expression of the 2A subunit of the N-methyl-D-aspartate receptor in enkephalin-positive and enkephalin-negative neurons

Striatal efferent neurons receive dopamine- and glutamate-utilizing afferents. Previous studies have shown that dopamine depletion increases gene expression in striatopallidal neurons and decreases it in striatonigral neurons. Previous work has also reported increased expression of the 2A subunit of the N-methyl-D-aspartate receptor in the dopamine-depleted striatum. The purpose of this study therefore was to determine whether dopamine depletion differentially alters the expression of the 2A subunit of the N-methyl-D-aspartate receptor in rat striatal neurons. 6-Hydroxydopamine (8microg/2microl) was infused unilaterally into the medial forebrain bundle. Rats were killed three weeks later. Double-label in situ hybridization was performed using an 35S-labeled ribonucleotide probe directed against the messenger RNA of the 2A subunit and a digoxigenin-labeled ribonucleotide probe directed towards preproenkephalin messenger RNA to mark striatopallidal neurons. Analysis of single-labeled film autoradiograms revealed a significant increase in the expression of 2A subunit messenger RNA in the ipsilateral, but not the contralateral, striatum of dopamine-depleted animals, consistent with other studies in the literature. Cellular analysis of 2A subunit expression indicated that as a consequence of dopamine depletion there is a significant increase in the expression of this subunit in both enkephalin-positive and enkephalin-negative neurons. From this study we conclude that dopamine depletion increases messenger RNA expression of the 2A subunit of the N-methyl-D-aspartate receptor in striatopallidal and presumed striatonigral (enkephalin-negative) neurons. Such alterations may affect the pharmacology and function of the resultant receptor, and thus alter glutamate transmission in both populations of medium spiny neurons after dopamine depletion.

Caucasian family with two independent mutations: 2594delC in BRCA1 and 5392delAG in BRCA2 gene

Germline mutations in two breast cancer susceptibility genes, BRCA1 and BRCA2, predispose individuals to early onset breast and ovarian cancer. The frequency of mutations in these genes in the general population is very low. Therefore, the prior probability of finding any family with mutations in both genes is even lower. This study reports the presence of two mutations, one in BRCA1 and a second in BRCA2, in a single family with variable expression. The BRCA1 mutation, 2594delC, was identified first in the proband. Analysis on a related family member with early onset bilateral breast cancer for the same mutation was negative. Further analysis on the same individual led to the identification of a second germline mutation, 5392delAG in BRCA2 gene in this family. Without the knowledge of the second mutation in this family, many asymptomatic individuals would have been given a negative test result and be falsely reassured. Further analysis reveals differential expression of the two mutations. The spectrum of cancers as well as the age of onset is variable between the mutations and the generations. Finally, the study exemplifies the fact that molecular analysis of a genetically heterogeneous disease can be very complex and requires a team effort of the patients and their family members, genetic counselors or referring physicians as well as the personnel from the testing laboratory.

Hyperinsulinism/hyperammonemia syndrome in children with regulatory mutations in the inhibitory guanosine triphosphate-binding domain of glutamate dehydrogenase

The hyperinsulinism/hyperammonemia (HI/HA) syndrome is a form of congenital hyperinsulinism in which affected children have recurrent symptomatic hypoglycemia together with asymptomatic, persistent elevations of plasma ammonium levels. We have shown that the disorder is caused by dominant mutations of the mitochondrial enzyme, glutamate dehydrogenase (GDH), that impair sensitivity to the allosteric inhibitor, GTP. In 65 HI/HA probands screened for GDH mutations, we identified 19 (29%) who had mutations in a new domain, encoded by exons 6 and 7. Six new mutations were found: Ser(217)Cys, Arg(221)Cys, Arg(265)Thr, Tyr(266)Cys, Arg(269)Cys, and Arg(269)HIS: In all five mutations tested, lymphoblast GDH showed reduced sensitivity to allosteric inhibition by GTP (IC(50), 60--250 vs. 20--50 nmol/L in normal subjects), consistent with a gain of enzyme function. Studies of ATP allosteric effects on GDH showed a triphasic response with a decrease in high affinity inhibition of enzyme activity in HI/HA lymphoblasts. All of the residues altered by exons 6 and 7 HI/HA mutations lie in the GTP-binding domain of the enzyme. These data confirm the importance of allosteric regulation of GDH as a control site for amino acid-stimulated insulin secretion and indicate that the GTP-binding site is essential for regulation of GDH activity by both GTP and ATP.

The cell cycle of Entamoeba invadens during vegetative growth and differentiation

The cell division cycle of Entamoeba invadens was studied during vegetative growth of trophozoites and during their differentiation into cysts. During vegetative growth of trophozoites, it was observed that DNA synthesis typically continued after one genome content had been duplicated. During encystation, DNA synthesis was arrested after 4n genome content had been synthesised. Using multi-parameter flow cytometry, the light scattering properties of cysts and trophozoites were studied. The cytoplasmic granularity, reflected by the side scatter of light, was proportional to DNA content of trophozoites, whereas cysts with similar DNA contents showed heterogeneity in their cytoplasmic granularity. Dynamic changes in the intracellular calcium pools were observed during differentiation of trophozoites to cysts. Comparison of E. invadens and Entamoeba histolytica cell cycles suggest that both organisms may have similar regulatory processes during cell division and differentiation. Since E. histolytica cannot be induced to encyst in axenic culture, analysis of the E. invadens cell cycle during encystation may be useful for identifying homologous processes in E.histolytica.

Effects of NMDA receptor antagonists on D1 dopamine receptor-mediated changes in striatal immediate early gene expression: evidence for involvement of pharmacologically distinct NMDA receptors?

Dopamine D1 receptor regulation of striatal gene expression is dependent on N-methyl-D-aspartate (NMDA) receptors. To determine whether pharmacologically distinct NMDA receptors are differentially involved, we examined the effects of different NMDA receptor antagonists on D1-induced immediate early gene expression. Systemic administration of the channel blocking antagonists MK-801 and dextrorphan and the competitive antagonist CGS 19755 blocked gene expression induced by the D1 agonist SKF 82958. The NMDA polyamine site antagonist ifenprodil, however, potentiated the effect of SKF 82958. Since ifenprodil is selective for receptors containing the NR2B subunit, the data suggest that subtypes of NMDA receptors may be differentially involved in regulating striatal function.

Clinical correlations of alpha2,6-sialyltransferase expression in colorectal cancer patients

We have previously demonstrated a link between alpha2,6-Sialyltransferase (alpha2,6-ST; E.C. 2.4.99.1) expression and differentiation of colon tumors. So far, information is not available relative to the expression of alpha2,6-ST in tumors and the survival of patients with colorectal cancer. We have examined the expression of alpha2,6-ST in a variety of colorectal adenocarcinomas (n = 46) at different stages of differentiation (G1 to G3) by immunoperoxidase assay using monoclonal antibody (MAb) 6B9. Clinical outcome of the patients in a 5-year follow-up study has been correlated with the expression of alpha2,6-ST in tumors surgically removed from the same patients. No significant difference in the alpha2,6-ST expression was noted when age, sex, and tumor locations (colon, rectum) were included as parameters. However, 52% of the moderate (G2) and well-differentiated (G1) adenocarcinomas showed stronger alpha2,6-ST expression compared with poorly differentiated (G3) adenocarcinomas. Notably, absence to moderate levels of tumor alpha2,6-ST expression was correlated with 100% survival in patients with stage I and II tumors compared with 64% survival in patients with strong tumor alpha2,6-ST expression (p < 0.01). These studies suggest a negative correlation between the expression of alpha2,6-ST in tumors and a good clinical outcome in colorectal cancer patients.

Effects of MK-801 on D1 dopamine receptor-mediated immediate early gene expression in the dopamine-depleted striatum

Previous work indicates that intrastriatal administration of MK-801 does not completely block D1 agonist-induced gene expression in dopamine-depleted rats. The present study examined the effects of systemic MK-801 on such gene expression. A low dose of MK-801 did not affect induction of c-fos or zif268. A high dose completely blocked induction of c-fos, but only slightly suppressed zif268. The data suggest that NMDA receptor activity may not always be necessary for D1-induced gene expression.

Detection of mutations in multi-exon genes: comparison of conformation sensitive gel electrophoresis and sequencing strategies with respect to cost and time for finding mutations

This report compares the relative advantages and disadvantages of two alternative strategies with respect to cost and time for finding mutations in the COL2A1 gene in patients with degenerative diseases of the joint. The coding region of the COL2A1 gene, 30 kb in length and containing 52 exons, can be analyzed using 26 genomic PCR products. The results indicate that the most efficient and cost effective way to screen large genes is a prescreen of the coding sequences followed by sequencing of a limited number of variant-PCR products.

Genetic testing for breast cancer susceptibility: frequency of BRCA1 and BRCA2 mutations

Genetic testing for breast cancer susceptibility became a reality after two cancer predisposition genes, BRCA1 and BRCA2, were identified. Mutations in these two genes were predicted to account for 85% to 90% of hereditary breast and ovarian cancer syndromes. We present results of mutation analysis of the coding sequence of these two genes in 110 consecutive non-Jewish breast cancer patients with a positive family history of breast and/or ovarian cancer. The individuals were identified in various cancer risk evaluation centers in the country. Twenty-two (20%) mutations in the BRCA1 gene and 8 mutations (7%) in the BRCA2 gene were detected. We also analyzed 52 Ashkenazi Jewish breast cancer patients for mutations in the BRCA1 and BRCA2 genes. Eleven Jewish individuals (21%) carried either one of the two common mutations, 185delAG and 5382InsC, in the BRCA1 gene and 4 individuals (8%) had the 6174delT mutation in the BRCA2 gene. The frequency of mutations in BRCA genes in affected people in this ethnic group was not significantly different from the non-Jewish population. On further analysis, the data demonstrate that neither age of onset nor phenotype of the disease had any significant predictive value for the frequency of mutations in these genes. These data confirm the lower prevalence of mutations in either of the BRCA genes in clinical families when compared to high-risk families used for obtaining linkage data in a research setting.

Fibulin-2 exhibits high degree of variability, but no structural changes concordant with abdominal aortic aneurysms

We used conformation sensitive gel electrophoresis and direct sequencing of PCR products to screen for mutations in the cDNA for fibulin-2, an extracellular matrix protein, from 11 patients with abdominal aortic aneurysms and two controls. When compared with the published reference sequence, a total of 14 single-base sequence variations were detected. Seven of the changes were neutral in that they did not result in an amino acid substitution. There were five missense changes at sites not conserved between human and mouse, and two missense changes at sites conserved between human and mouse. All but two of the sequence variants studied were also present in an additional set of 102 control alleles analyzed. One of these two changes was a missense mutation, but it did not segregate with abdominal aortic aneurysms in the family, whilst the other change was neutral. In conclusion, fibulin-2 has a large number of sequence variations in comparison with our previous analyses of type III collagen, and these variations will be useful in association studies. There was an excellent overall agreement between direct sequencing of PCR-products and conformation sensitive gel electrophoresis.

High throughput fluorescence-based conformation-sensitive gel electrophoresis (F-CSGE) identifies six unique BRCA2 mutations and an overall low incidence of BRCA2 mutations in high-risk BRCA1-negative breast cancer families

Mutational analysis of cancer susceptibility genes has opened up a new era in clinical genetics. In this report we present the results of mutational analysis of the BRCA2 coding sequences in 105 high-risk individuals affected with breast cancer and/or ovarian cancer and previously found to be negative for mutations of the BRCA1 coding sequence in our laboratory. These individuals have a positive family history with three or more cases of breast cancer and/or ovarian cancer at any age from the same side of the family tree. In order to perform a high throughput and reliable mutational analysis of the BRCA genes, we have adapted the conformation-sensitive gel electrophoresis mutation-scanning assay to a fluorescent platform. The advantages are speed, reproducibility and enhanced resolving power of the scanning method. Four unique mutations, including one missense and three frameshift mutations, were identified in the pool of 60 non-Jewish patients (7%). Two cases of the 6174delT mutation were identified in the 45 Ashkenazi Jewish individuals studied (5%). In addition, two novel frameshift mutations, not characteristic of the Jewish subgroup, were identified. Thus there were four mutations in total in this ethnic subgroup (9%). The six mutations identified in this combined patient pool, excluding the 6174delT mutations, are novel and have not been previously reported in the Breast Cancer Information Core (BIC) database. The results indicate that BRCA2 mutations account for the disease in less than 10% of this patient population. In addition, there is no significant difference in frequency of BRCA2 mutations between the Ashkenazi Jewish and non-Jewish families in our clinical patient pool.

BRCA1 mutations in women attending clinics that evaluate the risk of breast cancer

BACKGROUND

To define the incidence of BRCA1 mutations among patients seen in clinics that evaluate the risk of breast cancer, we analyzed DNA samples from women seen in this setting and constructed probability tables to provide estimates of the likelihood of finding a BRCA1 mutation in individual families.

METHODS

Clinical information, family histories, and blood for DNA analysis were obtained from 263 women with breast cancer. Conformation-sensitive gel electrophoresis and DNA sequencing were used to identify BRCA1 mutations.

RESULTS

BRCA1 mutations were identified in 16 percent of women with a family history of breast cancer. Only 7 percent of women from families with a history of breast cancer but not ovarian cancer had BRCA1 mutations. The rates were higher among women from families with a history of both breast and ovarian cancer. Among family members, an average age of less than 55 years at the diagnosis of breast cancer, the presence of ovarian cancer, the presence of breast and ovarian cancer in the same woman, and Ashkenazi Jewish ancestry were all associated with an increased risk of detecting a BRCA1 mutation. No association was found between the presence of bilateral breast cancer or the number of breast cancers in a family and the detection of a BRCA1 mutation, or between the position of the mutation in the BRCA1 gene and the presence of ovarian cancer in a family.

CONCLUSIONS

Among women with breast cancer and a family history of the disease, the percentage with BRCA1 coding-region mutations is less than the 45 percent predicted by genetic-linkage analysis. These results suggest that even in a referral clinic specializing in screening women from high-risk families, the majority of tests for BRCA1 mutations will be negative and therefore uninformative.

A-2-->G transition at the 3' acceptor splice site of IVS17 characterizes the COL2A1 gene mutation in the original Stickler syndrome kindred

Hereditary progressive arthro-ophthalmopathy, or "Stickler syndrome," is an autosomal dominant osteochondrodysplasia characterized by a variety of ocular and skeletal anomalies which frequently lead to retinal detachment and precocious osteoarthritis. A variety of mutations in the COL2A1 gene have been identified in "Stickler" families; in most cases studied thus far, the consequence of mutation is the premature generation of a stop codon. We report here the characterization of a COL2A1 gene mutation in the original kindred described by Stickler et al. [1965]. Conformational sensitive gel electrophoresis (CSGE) [Ganguly et al., 1993] was used to screen for mutations in the entire COL2A1 gene in an affected member from the kindred. A prominent heteroduplex species was noted in the polymerase chain reaction (PCR) product from a region of the gene including exons 17 to 20. Direct sequencing of PCR-amplified genomic DNA resulted in the identification of a base substitution at the A-2 position of the 3' splice acceptor site of IVS17. Sequencing of DNA from affected and unaffected family members confirmed that the mutation segregated with the disease phenotype. Reverse transcriptase-PCR analysis of poly A+ RNA demonstrated that the mutant allele utilized a cryptic splice site in exon 18 of the gene, eliminating 16 bp at the start of exon 18. This frameshift eventually results in a premature termination codon. These findings are the first report of a splice site mutation in classical Stickler syndrome and they provide a satisfying historical context in which to view COL2A1 mutations in this dysplasia.

Salutary effect of Terminalia Arjuna in patients with severe refractory heart failure

Twelve patients with refractory chronic congestive heart failure (Class IV NYHA), related to idiopathic dilated cardiomyopathy (10 patients); previous myocardial infarction (one patient) and peripartum cardiomyopathy (one patient), received Terminalia Arjuna, an Indian medicinal plant, as bark extract (500 mg 8-hourly) or matching placebo for 2 weeks each, separated by 2 weeks washout period, in a double blind cross over design as an adjuvent to maximally tolerable conventional therapy (Phase I). The clinical, laboratory and echocardiographic evaluation was carried out at baseline and at the end of Terminalia Arjuna and placebo therapy and results were compared. Terminalia Arjuna, compared to placebo, was associated with improvement in symptoms and signs of heart failure, improvement in NYHA Class (Class III vs. Class IV), decrease in echo-left ventricular enddiastolic (125.28 +/- 27.91 vs. 134.56 +/- 29.71 ml/m2; P < 0.005) and endsystolic volume (81.06 +/- 24.60 vs. 94.10 +/- 26.42 ml/m2; P < 0.005) indices, increase in left ventricular stroke volume index (44.21 +/- 11.92 vs. 40.45 +/- 11.56 ml/m2; P < 0.05) and increase in left ventricular ejection fractions (35.33 +/- 7.85 vs. 30.24 +/- 7.13%; P < 0.005). On long term evaluation in an open design (Phase II), wherein Phase I participants continued Terminalia Arjuna in fixed dosage (500 mg 8-hourly) in addition to flexible diuretic, vasodilator and digitalis dosage for 20-28 months (mean 24 months) on outpatient basis, patients showed continued improvement in symptoms, signs, effort tolerance and NYHA Class, with improvement in quality of life.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of angiotensin II- and potassium-mediated aldosterone secretion by KN-62 suggests involvement of Ca(2+)-calmodulin dependent protein kinase II in aldosterone secretion

Calcium is now acknowledged to play a major role as a cellular mediator of aldosterone secretion. However, the intricacies of the involvement of calcium in aldosterone secretion have not been clearly defined. We have shown here that calmodulin-dependent kinase II is involved in angiotensin II- and potassium-evoked aldosterone secretion as judged by the marked inhibitory effect of KN-62, a specific inhibitor of such a kinase, on aldosterone secretion and this inhibition was similar to that produced by calmodulin inhibitor, W-7. These results further strengthen the case for the participatory role of calcium-calmodulin system in aldosterone secretion.

Comparative effects of a highly specific protein kinase C inhibitor, calphostin C and calmodulin inhibitors on angiotensin-stimulated aldosterone secretion

We have examined the relative roles of the calcium-calmodulin system and protein kinase C in angiotensin-mediated aldosterone secretion. We used a highly specific protein kinase C inhibitor, calphostin C and two well-accepted calmodulin inhibitors, W-7 and calmidazolium. Although both types of inhibitors affected angiotensin-induced aldosterone secretion, as judged by the inhibitory doses of these compounds, angiotensin-evoked aldosterone secretion was more sensitive to calmodulin inhibition than protein kinase C inhibition. Manipulation of OFFracellular calcium by dantrolene and thapsigargin also modified aldosterone secretion significantly.

Targeted insertions of two exogenous collagen genes into both alleles of their endogenous loci in cultured human cells: the insertions are directed by relatively short fragments containing the promoters and the 5' ends of the genes

Previous studies demonstrated that type II procollagen is synthesized by HT-1080 cells that are stably transfected with constructs of the human COL2A1 gene that contain the promoter and 5' end of either the COL2A1 gene or the human COL1A1 gene. Since the host HT-1080 cells were from a human tumor line that synthesizes type IV collagen but not type II or type I procollagen, the results suggested that the constructs were integrated near active enhancers or promoters. Here, however, we demonstrate that a 33-kb construct of the COL2A1 gene containing a 5' fragment from the same gene was inserted into both alleles of the endogenous COL2A1 gene on chromosome 12, apparently by homologous recombination by a nonconservative pathway. In contrast, a similar construct of the COL2A1 gene in which the 5' end was replaced with a 1.9-kb fragment from the 5' end of the COL1A1 gene was inserted into both alleles of the locus for the COL1A1 gene on chromosome 17. Therefore, targeted insertion of the gene construct was not directed by the degree of sequence homology. Instead, it was directed by the relatively short 5' fragment from the COL1A1 gene that contained the promoter and the initially transcribed sequences of the gene. After insertion, both gene constructs were expressed from previously inactive loci.

Self-assembly into fibrils of collagen II by enzymic cleavage of recombinant procollagen II. Lag period, critical concentration, and morphology of fibrils differ from collagen I

A recently developed recombinant system for synthesis of human procollagen II by stably transfected host cells was used to prepare adequate amounts of protein to study the self-assembly of collagen II into fibrils. The procollagen II was cleaved to pCcollagen II by procollagen N-proteinase (EC 3.4.24.14), the pCcollagen II was chromatographically purified, and the pCcollagen II was then used as a substrate to generate collagen II fibrils by cleavage with procollagen C-proteinase. The kinetics for assembly of collagen II fibrils were similar to those observed previously for the self-assembly of collagen I in that a distinct lag phase was observed followed by a sigmoidal propagation phase. However, under the same experimental conditions, the lag time for assembly of collagen II fibrils was 5-6-fold longer, and the propagation rate for collagen II fibrils was about 30-fold lower than for collagen I fibrils. The relatively long lag time for the assembly of collagen II into fibrils made it possible to demonstrate that most of the conversion of pCcollagen II to collagen II occurred in the solution phase. The critical concentration at 37 degrees C for collagen II was about 50-fold greater than the critical concentration for collagen I. The Gibbs free energy change for the assembly of collagen II into fibrils was -40 kJ/mol, a value that was about 14 kJ/mol less than the free energy change for collagen I and about the same as the free energy change for the homotrimer of collagen I. Dark-field light microscopy and negative-staining electron microscopy demonstrated that the collagen II fibrils were thin and formed network-like structures. The results demonstrated, therefore, that the structural information of the monomer is sufficient to explain the characteristically small diameters and arcade-like geometry of collagen II fibrils found in cartilage and other tissues.

Roles of FSH and testosterone in the initiation of spermatogenesis in prepubertal rats medically hypophysectomized by a GnRH antagonist

Experimentally induced medical hypophysectomy in prepubertal rats through treatment of GnRH antagonist for 3 weeks, initiated on the 20th day of age, markedly decreased testicular weight by 85% of that of the controls. Quantitative assessment of spermatogenesis in testicular semithin preparations revealed a significant reduction in the numbers of preleptotene (27.2 +/- 1.6 to 15.6 +/- 0.52) and pachytene (25.8 +/- 0.96 to 5.35 +/- 0.26) spermatocytes and complete absence of any spermatids after the treatment. By contrast, round stage 7 and elongated spermatids were observed in many tubules of the testis in the age-matched control rats. At the end of GnRH antagonist treatment, the blood levels of LH were undetectable, while testosterone and FSH were decreased to 12 and 44% of the controls, respectively. Supplementation of either FSH (ovine FSH 20 micrograms/rat day-1) or testosterone (30 micrograms/rat day-1) enhanced the testicular weight (68%) and the circulatory levels of these hormones, but failed to support quantitatively normal spermatogenesis, which was, however, qualitatively improved. The number of maturing spermatids were comparatively higher in the testosterone-supplemented group that in the FSH-administered group. The latter group had otherwise the highest number of degenerating germ cells per tubule (mean 4.8 +/- 0.1). Testicular weight and stage-specific germ cell counts were restored to normalcy only in rats supplemented with both FSH and testosterone, the critical concentrations of which were important in the initial stages of spermatogenesis. Testosterone alone had a positive effect in terms of germ cell development, while FSH without testosterone was detrimental to the maturing germ cells.

Synthesis of recombinant human procollagen II in a stably transfected tumour cell line (HT1080)

Apparently because the biosynthetic pathways involve eight or more highly specific post-translational enzymes, it has been difficult to obtain expression of genes for fibrillar collagens in recombinant systems. Here two constructs of the human gene for procollagen II (COL2A1) were prepared, one with about 0.5 kb of a promoter for a procollagen I gene (COL1A1) and the other with about 4 kb of the promoter for the procollagen II gene. The constructs, together with a neomycin-resistant gene, were transfected into a human tumour cell line (HT1080) that synthesizes the collagen IV found in basement membranes, but does not synthesize any fibrillar collagen. About two per 100 clones resistant to the neomycin analogue G418 synthesized and secreted human procollagen II. Milligram quantities of the recombinant procollagen II were readily isolated from the cultured medium. The recombinant procollagen II had the expected amino acid sequence as defined by nucleotide sequencing of mRNA-derived cDNA and the expected amino acid composition as defined by analysis of procollagen II that was converted into collagen II by digestion with procollagen N- and C-proteinases. Also, analysis of the carbohydrate content indicated that there was glycosylation of some of the hydroxylysine residues but no evidence of post-translational overmodification of the residues. In addition, the protein was shown to have a native conformation as assayed by a series of protease digestions. No essential differences were found between clones transfected with the COL2A1 gene construct containing the COL1A1 promoter and the similar construct containing the COL2A1 promoter in terms of number of clones synthesizing recombinant procollagen II and the levels of expression. With both constructs, the expression of the COL2A1 gene was closely related to copy number. The results demonstrated therefore that it is not essential to use a promoter for a gene normally expressed in a host cell in order to obtain gene copy-number-dependent expression of an exogenous collagen gene in stably transfected cells.

Conformation-sensitive gel electrophoresis for rapid detection of single-base differences in double-stranded PCR products and DNA fragments: evidence for solvent-induced bends in DNA heteroduplexes

Several techniques have recently been developed to detect single-base mismatches in DNA heteroduplexes that contain one strand of wild-type and one strand of mutated DNA. Here we tested the hypothesis that an appropriate system of mildly denaturing solvents can amplify the tendency of single-base mismatches to produce conformational changes, such as bends in the double helix, and thereby increase the differential migration of DNA heteroduplexes and homoduplexes during gel electrophoresis. The best separations of heteroduplexes and homoduplexes were obtained with a standard 6% polyacrylamide gel polymerized in 10% ethylene glycol/15% formamide/Tris-taurine buffer. As predicted by the hypothesis of solvent-induced bends, when the concentration of either ethylene glycol or formamide was increased, the differential migration decreased. Also, single-base mismatches within 50 bp of one end of a heteroduplex did not produce differential migration. Sixty of 68 single-base mismatches in a series of PCR products were detected in some 59 different sequence contexts. The eight mismatches not detected were either within 50 bp of the nearest end of the PCR product or in isolated high-melting-temperature domains. Therefore, it was possible to predict in advance the end regions and sequence contexts in which mismatches may be difficult to detect. The procedure can be applied to any PCR products of 200-800 bp and requires no special equipment or preparation of samples.

Is testosterone essential for maintenance of normal morphology in immature rat Leydig cells?

Selective deprivation of gonadotrophins in prepubertal rats by administration of a GnRH antagonist (Ac-D2Nal1, D4ClPhe2, DTrp3, DArg6, DA1a10-GnRH; GnRH code: 103-289-10, National Institutes of Health, USA) for 3 weeks, initiated at 20-22 days of age, induced morphological changes in the Leydig cells, including thickening and indentation of the nuclear margin, pyknosis and elongation of the nuclei. Mean nuclear diameter was reduced to 22% of that in the controls. Under the electron microscope the cells exhibited reduced volume of the nucleus and cytoplasm and the plasma membrane was irregular. This abnormal appearance of the Leydig cells improved marginally in 20-30% of the Leydig cells and their mean nuclear diameter increased to 39% of the control level after FSH supplementation (20 micrograms ovine FSH/day). Normal morphological integrity of the Leydig cells consisting of round or oval nuclei, a smooth nuclear and cellular margin and the original mean nuclear diameter was restored completely when testosterone (30 micrograms/day) was administered to GnRH antagonist-treated rats, with or without simultaneous administration of FSH; in these rats testosterone levels in blood were also restored to normal. These findings indicate that testosterone may be important for the maintenance of normal Leydig cell morphology in the rat.

Atrial natriuretic peptide-induced inhibition of aldosterone secretion: a quest for mediator(s)

Atrial natriuretic peptide (ANP) inhibits aldosterone secretion evoked by its physiological secretagogues by a mechanism(s) likely to involve intracellular messengers. When one examines the results of various investigations so far, this premise, although not definitive yet, seems to be supported. Therefore a brief perspective on the cellular messengers of the various secretagogues is provided before the inquiry into the possible mechanism of action of ANP. The receptors of ANP in the adrenal cells have been identified and characterized. ANP inhibits adenylate cyclase in various tissues through an inhibitory G protein, which appears to explain in part the inhibitory effect of ANP on adrenocorticotropin-induced aldosterone secretion. However, there could be other possible effects of ANP as discussed. ANP probably inhibits aldosterone secretion evoked by angiotensin II and potassium by interfering with the appropriate changes in calcium flux and cell calcium concentration, concomitants of stimulation by these secretagogues. The potential modes of these effects are probed. The role of guanosine 3',5'-cyclic monophosphate, which is increased by receptor activation of guanylate cyclase by ANP and is thought to play a major role in the biological effects of ANP in some other tissues, remains controversial in the aldosterone-lowering effect of ANP, and this is also discussed extensively in this review.