Nerve Conduction and Heart Rate variability in Patients with Hypothyroidism at a Tertiary Care Centre in Eastern Nepal.

INTRODUCTION: Thyroid hormone effects on many organs including central and peripheral nervous systems. However, these hormones do not affect all systems/organs to a similar extent. Thus, we conducted this study to explore the effect of thyroid hormones on somatic nervous system assessed by Nerve conduction study and cardiac autonomic activity assessed by heart rate variability. METHODS: The study included newly diagnosed hypothyroid patients and healthy controls. In all subjects NCS were performed in median, ulnar, tibial and sural nerves using Nihonkohden machine Cardiac autonomic control was assessed using Short-term Heart Rate Variability and parameters were analyzed by Time Domain and Frequency Domain methods. RESULTS: Both the groups were comparable in term of age, Body Mass Index, Pulse Rate, Systolic Blood Pressure and Diastolic Blood Pressure. Sensory parameters of NCS showed significant decrease in left median nerve SNAP amplitude (38.24±10.23 Vs 31.59±14.06, P=0.048) and nerve conduction velocity of bilateral median nerve in hypothyroid patients. In motor parameters of NCS, onset latencies of bilateral median nerves and right ulnar nerve were significantly increased in hypothyroid patients. All Time Domain measures of HRV and Frequency Domain measures; LF Power, HF Power and Total Power were significantly decreased (P<0.05) in hypothyroid patients. These HRV parameters are indicators of parasympathetic activity. CONCLUSIONS: In newly diagnosed hypothyroid patients, especially median nerve functions (both sensory and motor) and parasympathetic activity were decreased. It reflects that in hypothyroidism both autonomic nervous system and other somatic nerves are not affected in a similar extent.

Bleeding and liver transplantation outcomes in haemophilia.

BACKGROUND: Hepatitis C is the major cause of end-stage liver disease and the major indication for orthotopic liver transplantation (OLTx) in individuals with haemophilia. AIM: To assess the epidemiology and outcomes of OLTx in U.S. haemophilia patients. METHODS: We investigated haemophilia liver transplant recipients between 1993 and 2012, using the Nationwide Inpatient Sample, identified by ICD9 code 50.59. RESULTS: Of the 11 267 (weighted n = 54 691) patients undergoing OLTx, 44 (0.4%; weighted n = 213) had haemophilia. Those with haemophilia were more likely than non-haemophilic OLTx recipients to have bleeding complications (45.3% vs. 31.5%, P = 0.009) and hypovolemic shock (7.0% vs. 1.1%, P < 0.0001). They also had a significantly higher incidence of HIV (24.8% vs. 0.5%, P < 0.005), hepatitis B (16.2% vs. 7.9%, P = 0.04) and vitamin K deficiency (2.1% vs. 0.02%, P < 0.001). In spite of these differences, there was no difference in in-hospital mortality between haemophilic and non-haemophilic recipients (6.8% vs. 6.2%, P = 0.9). In multivariate logistic regression, bleeding complications in haemophilia increased the risk of in-hospital mortality by more than 3-fold (P < 0.0001), and disseminated intravascular coagulation increased the risk of bleeding complications in haemophilic recipients by over 10-fold (P < 0.0001). CONCLUSIONS: Bleeding complications are common in haemophilia OLTx recipients. Thus, aggressive correction of coagulation defects in this group may be a medically sound approach to reduce complications and mortality associated with OLTx.

Substitute of Animals in Drug Research: An Approach Towards Fulfillment of 4R's.

The preclinical studies for drug screening involve the use of animals which is very time consuming and expensive and at times leads to suffering of the used organism. Animal right activists around the world are increasingly opposing the use of animals. This has forced the researchers to find ways to not only decrease the time involved in drug screening procedures but also decrease the number of animals used and also increase the humane care of animals. To fulfill this goal a number of new in vitro techniques have been devised which are called 'Alternatives' or 'Substitutes' for use of animals in research involving drugs. These 'Alternatives' are defined as the adjuncts which help to decrease the use as well as the number of animals in biomedical research. Russell and Burch have defined these alternatives by three R's - Reduction, Refinement and Replacement. These alternative strategies include physico-chemical methods and techniques utilizing tissue culture, microbiological system, stem cells, DNA chips, micro fluidics, computer analysis models, epidemiological surveys and plant-tissue based materials. The advantages of these alternatives include the decrease in the number of animals used, ability to obtain the results quickly, reduction in the costs and flexibility to control the variables of the experiment. However these techniques are not glittering gold and have their own shortcomings. The disadvantages include the lack of an appropriate alternative to study the whole animal's metabolic response, inability to study transplant models and idiosyncratic responses and inability to study the body's handling of drugs and its subsequent metabolites. None-the-less these aalternative methods to certain extent help to reduce the number of animals required for research. But such alternatives cannot eliminate the need for animals in research completely. Even though no animal model is a complete set of replica for a process within a human body, the intact animal does provide a better model of the complex interaction of the physiological processes.

Hyperglycemia, glucose intolerance, hypertension and socioeconomic position in eastern Nepal.

Abstract. The present study was undertaken to evaluate differences between urban and rural Nepali populations in terms of hyperglycemia, socioeconomic position (SEP) and hypertension, through a community based survey in Sunsari District, eastern Nepal. Blood glucose levels were measured in participants (N = 2,006) S30 years old from urban and rural communities and were classified according to WHO criteria (1998) into normoglycemia (NGY), impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and hyperglycemia (HGY). SEP was assessed by structured health interview along with anthropometric measurements and behavioral variables. Hypertension was classified per Joint National Committee (JNC-VII) criteria. Ten point three percent and 11.9% of subjects in this survey (13.3% urban and 11.0% rural) gave a family history and personal history of diabetes mellitus, respectively. Of urban participants (n = 736) with no history of diabetes 70 (9.5%) had HGY and 143 (19.4%) had glucose intolerance (IFG and IGT). Of rural participants (n = 1,270) 114 (9.0%) had HGY and 176 (13.9%) had glucose intolerance. There was an increasing trend in numbers of cases of hyperglycemia and intolerance with increasing age (chi2 198.2, p < 0.001), body mass index (BMI) (chi2 35.1, p < 0.001), SEP (chi2 48.5, p < 0.001) and hypertension (chi2 130.6, p < 0.001). Rural participants had a lower odds ratio [0.706; 95% confidence interval (CI) 0.455-1.096] of having hyperglycemia than urban participants. Individuals with medium and higher SEP had a lower odds ratio (0.878; CI 0.543-1.868) and higher odds ratio (1.405; CI 0.798-2.474), respectively, compared to individuals with lower SEP of having HGY. Both urban and rural populations are at risk for hyperglycemia and glucose intolerance. Individuals having a medium SEP had lower risk of diabetes mellitus than individuals from lower and higher SEP.

Subclinical hypothyroidism in eastern Nepal: a hospital based study.

BACKGROUND: Subclinical hypothyroidism itself is associated with serious complications and also there is a known risk of subclinical hypothyroidism patients getting converted into overt disease. OBJECTIVES: The objective of the present study was to fi nd out the prevalence of subclinical hypothyroidism in the suspected cases i.e. amongst the cases attending the thyroid laboratory at B.P. Koirala Institute of Health Sciences, Dharan, Nepal. MATERIALS AND METHODS: It was a retrospective cross sectional study. Data of the free T3, free T4 and TSH estimations of the year 2007 of the Thyroid lab at BPKIHS, Dharan, Nepal was analyzed. ELISA based free T3, free T4 and TSH tests in the serum had been performed in all the cases. RESULTS: Total cases were 1714 including 24.446% males and 75.554% females. Cases with raised TSH levels were 26.021%, cases with normal TSH levels were 54.66% and cases with low TSH levels were 19.316%. Total 350 cases (20.42 %) had subclinical hypothyroid dysfunction which includes 84 (4.901 %) males and 266 (15.519%) females. And the maximum percentage of cases in either gender was between the age groups 20 -59 years. CONCLUSION: The prevalence of subclinical thyroid hypothyroidism amongst the suspected cases was 20.42 % which is much higher compared to the other parts of the world. The highest percentage was found in the female age group 20 - 59 years. The routine screening of the whole population is not cost effective and on the basis of the present study it is suggested that there may be routine screening of the selected populations, especially women between 20 to 59 years of age in Nepal region. The preferred screening method advised is a sensitive ELISA based TSH test.

Diagnosis of multiple myeloma by demonstration of M protein in bone marrow aspirate by agar gel electrophoresis: a case report.

A number of laboratory tests are used to confirm the diagnosis of multiple myeloma, including M protein in the serum. Since M protein in the serum originate from tumour cells in the bone marrow before circulating in the serum, demonstration of M protein in bone marrow aspirate can be added to the batteries of diagnostic parameters.

Adenosine deaminase activity in sera of patients with visceral leishmaniasis in Nepal.

This longitudinal study was conducted in BP Koirala Institute of Health Sciences (BPKIHS), a Medical University situated in eastern Nepal, between May 2001 and December 2001. The main objective of the study was to identify the role of adenosine deaminase (ADA) activity in patients with visceral leishmaniasis (VL) for management. There was a significant increase in mean ADA activity in sera of 49 patients with VL (323.71+/-184.51 IU/L) compared with 50 samples of control groups (47.11+/-24.94 IU/L) from the same endemic area (P < 0.001). ADA activities were found to be significantly decreased (50.35+/-41.35 IU/L) in follow-up cases (n = 19) after 30 days with sodium stibogluconate treatment at a dose of 20 mg/kg/day intramuscularly. The fall in the level of ADAF (after treatment) in follow-up cases correlated with the cure of disease, as evident from improvement of vital signs and symptoms and the absence of Leishmania donavani bodies in the sera. The study therefore suggests the possibility of using human serum ADA as a convenient marker to evaluate the diagnosis of VL to support the clinical findings, especially in those settings where there is a lack of highly qualified personnel and diagnostic facilities.

Critical role of p42/44(MAPK) activation in anisomycin and hepatocyte growth factor-induced LDL receptor expression: activation of Raf-1/Mek-1/p42/44(MAPK) cascade alone is sufficient to induce LDL receptor expression.

The protein synthesis inhibitor anisomycin activates stress-related mitogen-activated protein kinases (MAPKs), namely, c-jun NH(2)-terminal kinase (p46/54(JNK)) and p38(MAPK) in mammalian cells. In this paper, we show that although exposure to anisomycin resulted in rapid and strong activation of p46/54(JNK) and p38(MAPK), with a delayed low level dual-phosphorylation of mitogen/extracellular protein kinase (p42/44(MAPK)), low density lipoprotein (LDL) receptor induction depends solely on the mild activation of p42/44(MAPK) signaling cascade in HepG2 cells. Unlike hepatocyte growth factor (HGF) which caused LDL receptor induction via rapid, strong, and Ras-dependent p42/44(MAPK) activation, anisomycin-induced p42/44(MAPK) activity and increased LDL receptor expression in a Ras-independent manner. Finally, we examined the role of the p42/44(MAPK) signaling cascade in LDL receptor induction by activating this kinase independently of anisomycin or HGF. By using estrogen-dependent human Raf-1 protein kinase in transient transfection assays, we show that the exclusive activation of the Raf-1/MEK-1/p42/44(MAPK) signaling cascade with antiestrogen ICI 182, 780 caused induction of LDL receptor expression to the same level as observed with either HGF or anisomycin. Consistent with the role of p42/44(MAPK), induction was strongly inhibited by pretreatment with the MEK-1/2 inhibitor PD98059. Our observation that anisomycin can use p42/44(MAPK) signaling cascade is a departure from established thinking, and the results presented shows that activation of the p42/44(MAPK) alone is sufficient to fully induce LDL receptor transcription.

One-way cross-talk between p38(MAPK) and p42/44(MAPK). Inhibition of p38(MAPK) induces low density lipoprotein receptor expression through activation of the p42/44(MAPK) cascade.

In this paper, we report that SB202190 alone, a specific inhibitor of p38(MAPK), induces low density lipoprotein (LDL) receptor expression (6-8-fold) in a sterol-sensitive manner in HepG2 cells. Consistent with this finding, selective activation of the p38(MAPK) signaling pathway by expression of MKK6b(E), a constitutive activator of p38(MAPK), significantly reduced LDL receptor promoter activity. Expression of the p38(MAPK) alpha-isoform had a similar effect, whereas expression of the p38(MAPK) betaII-isoform had no significant effect on LDL receptor promoter activity. SB202190-dependent increase in LDL receptor expression was accompanied by induction of p42/44(MAPK), and inhibition of this pathway completely prevented SB202190-induced LDL receptor expression, suggesting that p38(MAPK) negatively regulates the p42/44(MAPK) cascade and the responses mediated by this kinase. Cross-talk between these kinases appears to be one-way because modulation of p42/44(MAPK) activity did not affect p38(MAPK) activation by a variety of stress inducers. Taken together, these findings reveal a hitherto unrecognized one-way communication that exists between p38(MAPK) and p42/44(MAPK) and provide the first evidence that through the p42/44(MAPK) signaling cascade, the p38(MAPK) alpha-isoform negatively regulates LDL receptor expression, thus representing a novel mechanism of fine tuning cellular levels of cholesterol in response to a diverse set of environmental cues.

Inhibition of stress-activated p38 mitogen-activated protein kinase induces low-density lipoprotein receptor expression.

We have recently shown that different signal transduction pathways initiated by a variety of agents converge on growth-responsive p42/44MAPK signaling cascade to induce low-density lipoprotein (LDL) receptor expression. Our recent demonstration that stress-activated p38MAPK negatively regulates LDL receptor expression in an isoform-specific manner via modulation of p42/44MAPK cascade represents a new dimension of complexity in the molecular communication that governs LDL receptor expression. The suggested one-way communication between p38MAPK and p42/44MAPK provides a potential mechanism for fine-tuning cellular levels of cholesterol in response to a diverse set of environmental cues, including stress. Cross talk between MAPKs opens new avenues toward understanding a variety of pathogenic processes; this makes them tempting targets for therapeutic interventions in cardiovascular diseases.

Differential roles of extracellular signal-regulated kinase-1/2 and p38(MAPK) in interleukin-1beta- and tumor necrosis factor-alpha-induced low density lipoprotein receptor expression in HepG2 cells.

The inflammatory cytokines interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF), elevated in inflammatory, malignant, and infectious diseases, induce low density lipoprotein (LDL) receptor transcription in HepG2 cells, and such an induction can account for hypocholesterolemia associated with these states. However, the signaling mechanisms of cytokine-mediated LDL receptor induction are largely unexplored. In the present studies, we examined the potential involvement of different mitogen-activated protein kinase (MAPK) pathways. Northern analysis demonstrated that IL-1beta or TNF significantly increased LDL receptor transcript in HepG2 cells, whereas expression of another tightly regulated sterol-responsive squalene synthase gene was unaffected. IL-1beta treatment resulted in transient activation of three MAPK cascades, namely p46/54(JNK), p38(MAPK), and ERK-1/2, with maximal activation of 20-, 25-, and 3-fold, respectively, occurring 15-30 min after cytokine addition. PD98059, a specific inhibitor of MAPK kinase activity, inhibited IL-1beta-induced LDL receptor expression. In contrast, SB202190, a specific inhibitor of p38(MAPK), enhanced IL-1beta-induced LDL receptor expression, with a concomitant increase in ERK-1/2 activity. Similarly, TNF induced LDL receptor expression also required ERK-1/2 activation. Finally, sterols repressed IL-1beta induced receptor expression, without affecting ERK-1/2 activation. These results show that IL-1beta- or TNF-induced LDL receptor expression requires ERK-1/2 activation, that the p38(MAPK) pathway negatively regulates LDL receptor expression, and that sterols inhibit induction at a point downstream of ERK-1/2 in HepG2 cells.

Genetic complexity of the human geranylgeranyltransferase I beta-subunit gene: a multigene family of pseudogenes derived from mis-spliced transcripts.

Geranylgeranyltransferase I controls the function of a variety of cellular proteins by attaching a geranylgeranyl group to the carboxy-terminus of proteins. The purified enzyme from rat brain is comprised of two polypeptides, a catalytic alpha-subunit (GGTalpha) and a substrate-binding beta-subunit (GGTbeta). The present paper demonstrates the existence of a GGTbeta multigene family in humans by describing the presence and characterization of at least 13 pseudogenes related to this protein. Sequencing of numerous PCR-derived clones, obtained following amplification of human genomic DNA, revealed multiple, distinct but highly related sequences. All clones had a common deletion of 99-bp that conforms to the GT-AG rule of splicing in eukaryotes, and differed from the human GGTbeta cDNA sequence by multiple nucleotide substitutions. PCR amplification from mRNA, however, yielded only the sequence expected for the expressed GGTbeta protein. This apparent paradox was resolved by cloning and sequencing a complete GGTbeta-specific pseudogene. Multiple features of the cloned gene, in particular the absence of introns, presence of flanking direct repeats, and the lack of sequence similarity with the untranscribed region of the gene, indicate that this clone represents a processed pseudogene possibly resulting from a mis-spliced transcript. Multiple GGTbeta-specific pseudogenes appear to have resulted from more than one retroposition event. These results suggest a potential role for mis-splicing in the evolutionary diversity of pseudogenes.

Phorbol ester-induced low density lipoprotein receptor gene expression in HepG2 cells involves protein kinase C-mediated p42/44 MAP kinase activation.

The signaling pathway involved in low density lipoprotein (LDL) receptor gene expression induced by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) was investigated in the human hepatoma HepG2 cell line. Treatment of HepG2 cells with 100 nM TPA resulted in an approximately 20-fold increase in LDL receptor mRNA level, as determined by RT-PCR, which peaked at 2-4 h of treatment and subsequently declined. The protein kinase C (PKC) inhibitors calphostin C and staurosporine prevented TPA-mediated LDL receptor mRNA induction. In contrast, TPA did not affect squalene synthase mRNA expression. Immunoblotting of cell extracts with isozyme-specific PKC antibodies revealed that HepG2 cells expressed PKC alpha, which was mainly cytosolic, and PKC beta, PK epsilon, and PKC zeta, all of which were present in both the cytosolic and particulate fractions. Treatment of HepG2 cells with 100 nM TPA resulted in translocation of cytosolic PKC alpha to the particulate fraction, with a maximum at 30 min-2 h of treatment, but was without effect on the subcellular distribution of the other isozymes. TPA treatment also led to activation of the mitogen-activated protein kinase (MAPK) ERK cascade. The specific MAPK pathway inhibitor PD98059 blocked TPA-induced ERK activation. Furthermore, pretreatment of cells with PD98059 inhibited TPA-induced LDL receptor mRNA induction. Moreover, pretreatment of cells with calphostin C inhibited TPA-mediated ERK activation and LDL receptor mRNA induction in a dose-dependent fashion. Based on a close kinetic correlation between PKC alpha translocation and ERK activation, and the effects of specific inhibitors, these findings suggest that translocation/activation of PKC alpha, and subsequent activation of the Raf-1/MEK/ERK MAPK cascade, represent key events in the transcriptional induction of LDL receptor gene by TPA in HepG2 cells.

Identification of essential nucleotides of the FP1 element responsible for enhancement of low density lipoprotein receptor gene transcription.

Low density lipoprotein (LDL) receptor gene is regulated at the transcriptional level by the intracellular level of sterols in animal cells. We have recently identified a 20 bp long region (-145 to -126), designated Footprint 1 (FP1), participating in maximal expression of the human LDL receptor gene in the absence of sterols in HepG2 cells [Mehta, K. D., Chang, R., Underwood, J., Wise, J. and Kumar, A. (1996) J. Biol. Chem ., 271, 33616-33622]. To determine the minimal FP1 sequence and to define the critical nucleotides required for function, a series of single nucleotide substitutions were introduced in the FP1 region. Twenty-three independent mutations were analyzed by transfection into HepG2 cells. These studies localize the regulatory region to 14 bp and demonstrate the requirement for essential guanine nucleotides at positions -135 and -136 for FP1 function. Furthermore, transfection studies suggest that the FP1-dependent increase in reporter gene expression is possibly mediated through interaction with the sterol-regulatory element. UV cross-linking and Southwestern blot analysis identified FP1-binding factors of approximately 50 and 125 kDa, which we have denoted p50 and p125. Mutations of the critical guanine residues (-135/-136) decreased the formation of the specific protein-DNA complex with the FP1 sequence and abolished its binding to the p125. We conclude that direct interaction of the p125 factor with these nucleotides of the FP1 element potentially contributes to FP1-dependent induction of LDL receptor gene expression.

p21ras farnesyltransferase alpha- and beta-subunits are phosphorylated in PC-12 cells: TGF-beta signaling pathway independent phosphorylation.

Farnesyltransferase (FTase) catalyzes the transfer of a farnesyl isoprenoid to the conserved carboxyl-terminal cysteine residue of proteins terminating with the CAAX sequence. Rat brain FTase is a heterodimer consisting of a 49 kDa alpha-subunit and a 46 kDa beta-subunit. In this report, we show, for the first time, that the beta-subunit of FTase is phosphorylated in vivo and the FTase heterodimer contains phosphorylated alpha/beta-subunits in rat adrenal medulla pheocytochroma PC-12 cells. The presence of the phosphorylated FTase subunits as heterodimer in PC-12 cells which are known to be deficient in TGF-beta signaling pathways argues against the involvement of this pathway in their phosphorylation and heterodimerization.

Expression of the farnesyltransferase beta-subunit gene in human ovarian carcinoma: correlation to K-ras mutation.

The ras signaling protein requires a posttranslational modification to localize it to the inner surface of plasma membrane. In this state it can behave as a signal transduction mediator. Farnesyltransferase plays an important role in this posttranslational processing of ras by attaching a farnesyl group to the cysteine of the ras C-terminal tetrapeptide. In this study, we investigated the relationship of K-ras expression and mutation with farnesyltransferase beta-subunit expression in 20 ovarian tumors (17 carcinomas and 3 low malignant potential tumors) and 4 normal ovaries. The expression level of mRNA was determined by using quantitative PCR and mutation analysis was performed by direct cDNA sequencing. K-ras mutations were found in 1 of 3 low malignant potential tumors and in 4 of 17 carcinoma cases. K-ras mRNA overexpression was found in 1 of 3 low malignant potential tumors (one with mutated ras) and in only 1 of 17 carcinoma cases. Farnesyltransferase beta-subunit mRNA overexpression was found in 2 of 3 low malignant potential tumors and in 7 of 17 carcinoma cases. Interestingly, all K-ras mutation cases showed farnesyltransferase beta-subunit overexpression. These findings suggest that there may be a direct relationship between K-ras (ras dysfunction) mutation and expression of farnesyltransferase beta-subunit gene.

Identification of a novel cis-acting element participating in maximal induction of the human low density lipoprotein receptor gene transcription in response to low cellular cholesterol levels.

In this paper, we present both in vivo and in vitro evidence for the presence of a novel cis-acting regulatory element that is required for maximal induction of the human low density lipoprotein (LDL) receptor gene following depletion of cellular sterols in HepG2 cells. First, in vivo dimethyl sulfate footprinting of the human LDL receptor promoter before and after transcriptional induction in HepG2 cells revealed protection from -145 to -126, 5'-GAGCTTCACGGGTTAAAAAG-3' (referred to as FP1 site). Second, transient transfections of HepG2 cells with promoter luciferase reporter constructs containing the FP1 site resulted in significant enhancement (approximately 375%) of reporter gene expression in response to low levels of sterols compared with parallel plasmid without the FP1 site. In addition, this response was markedly attenuated on nucleotide substitutions within the FP1 site. Third, by electrophoretic mobility shift assays, the FP1 sequence was found to bind protein(s) from HepG2 nuclear extracts in a sequence-specific manner. In vitro binding of the FP1 mutants paralleled the results obtained for their in vivo transcription. On the basis of competition profiles, the FP1-binding factor is different from the known transcription factors binding to the AT-rich CArG and GArC motifs. Furthermore, the FP1-binding protein is not specific to HepG2 cells because nuclear factor(s) with the same specificity was observed in nuclear extracts of non-hepatic HeLa cells. We conclude that transcriptional induction of the LDL receptor gene in response to sterol depletion is mediated, in part, by an highly conserved novel cis-acting element through the binding of specific nuclear protein(s).

Alpha-subunit of farnesyltransferase is phosphorylated in vivo: effect of protein phosphatase-1 on enzymatic activity.

Farnesyltransferase is a heterodimer consisting of a 49 kDa alpha-subunit and a 46 kDa beta-subunit. In this report, we demonstrate that the endogenous heterodimeric farnesyltransferase protein is phosphorylated at the alpha-subunit in vivo and phosphorylation plays a role in the regulation of farnesyltransferase activity. In vivo 32P-labeling of PC-12 cells followed by immunoprecipitation with specific anti rat alpha-subunit IgG showed a labeled alpha-subunit protein band at an expected molecular mass of 49 kDa. Treatment of PC-12 cells with protein phosphatase inhibitor, Calyculin A, resulted in a decrease in FTase activity, and phophoserine/phosphothreonine-specific protein phosphatase-1 treatment of PC-12 and GM37 cell extracts resulted in 100% and 375% increase in farnesyltransferase activity, respectively, compared to untreated extracts.

Chiloscyllium plagiosum low-density lipoprotein receptor: evolutionary conservation of five different functional domains.

All five functional domains of the low-density lipoprotein (LDL) receptor were assembled in their modern form more than 450 million years ago, as revealed from the cloning and sequencing of an LDL receptor cDNA from Chiloscyllium plagiosum (banded cat shark). The shark LDL receptor has the same overall architecture as the mammalian and amphibian counterparts. Each of the seven cysteine-rich repeats in the ligand binding domain resembles its counterpart in the human LDL receptor more than it does the other repeats in the shark receptor as suggested by the presence of unique "signature" sequences, indicating that these repeats had already acquired their independent structures by the time of shark development. Furthermore, amino acid sequences of the entire ligand binding domain of shark LDL receptor show 35% identity over a stretch of 294 residues with a Lymnaea stagnalis G-protein-linked receptor (LSGLR). The region of homology between these unrelated proteins includes conservation of most of the unique characteristics of the cysteine-rich repeats of LDL receptor at the expected positions in LSGLR. The results presented are consistent with the hypothesis that all seven repeats in the ligand binding domain of LDL receptor may have been lifted directly from an ancestral gene instead of being evolutionary duplications of a single repeat recruited by the primitive LDL receptor from another gene.

In vivo role of the Sp1 site neighboring sterol-responsive element-1 in controlling low-density lipoprotein receptor gene expression.

The in vivo role of the crucial Sp1 site neighboring sterol-responsive element-1 (SRE-1) in controlling LDL receptor gene expression in the presence or absence of sterols was examined. For this purpose the Xenopus laevis system was utilized as there are two different genes for LDL receptors in frogs which differ in their promoter region in the Sp1-binding sequence of repeat 3 present immediately adjacent to SRE-1. DNase I footprinting of promoters of both receptors showed differences in the affinity of this Sp1 site to purified transcription factor Sp1. Transcript levels of both LDL receptors were measured in livers of frogs on normal and cholesterol-enriched diets. Basal levels and extent of repression of LDL receptor gene on sterol administration were found to be dependent on the nature of the Sp1 site of repeat 3 under in vivo conditions. We conclude that this Sp1 site acts as a constitutive positive transcriptional element that forms a part of the active transcription complex irrespective of cellular sterol levels.