Association of Immunosuppression and Viral Load With Subcortical Brain Volume in an International Sample of People Living With HIV

IMPORTANCE

Despite more widely accessible combination antiretroviral therapy (cART), HIV-1 infection remains a global public health challenge. Even in treated patients with chronic HIV infection, neurocognitive impairment often persists, affecting quality of life. Identifying the neuroanatomical pathways associated with infection in vivo may delineate the neuropathologic processes underlying these deficits. However, published neuroimaging findings from relatively small, heterogeneous cohorts are inconsistent, limiting the generalizability of the conclusions drawn to date.

OBJECTIVE

To examine structural brain associations with the most commonly collected clinical assessments of HIV burden (CD4+ T-cell count and viral load), which are generalizable across demographically and clinically diverse HIV-infected individuals worldwide.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study established the HIV Working Group within the Enhancing Neuro Imaging Genetics Through Meta Analysis (ENIGMA) consortium to pool and harmonize data from existing HIV neuroimaging studies. In total, data from 1295 HIV-positive adults were contributed from 13 studies across Africa, Asia, Australia, Europe, and North America. Regional and whole brain segmentations were extracted from data sets as contributing studies joined the consortium on a rolling basis from November 1, 2014, to December 31, 2019.

MAIN OUTCOMES AND MEASURES

Volume estimates for 8 subcortical brain regions were extracted from T1-weighted magnetic resonance images to identify associations with blood plasma markers of current immunosuppression (CD4+ T-cell counts) or detectable plasma viral load (dVL) in HIV-positive participants. Post hoc sensitivity analyses stratified data by cART status.

RESULTS

After quality assurance, data from 1203 HIV-positive individuals (mean [SD] age, 45.7 [11.5] years; 880 [73.2%] male; 897 [74.6%] taking cART) remained. Lower current CD4+ cell counts were associated with smaller hippocampal (mean [SE] β = 16.66 [4.72] mm3 per 100 cells/mm3; P < .001) and thalamic (mean [SE] β = 32.24 [8.96] mm3 per 100 cells/mm3; P < .001) volumes and larger ventricles (mean [SE] β = -391.50 [122.58] mm3 per 100 cells/mm3; P = .001); in participants not taking cART, however, lower current CD4+ cell counts were associated with smaller putamen volumes (mean [SE] β = 57.34 [18.78] mm3 per 100 cells/mm3; P = .003). A dVL was associated with smaller hippocampal volumes (d = -0.17; P = .005); in participants taking cART, dVL was also associated with smaller amygdala volumes (d = -0.23; P = .004).

CONCLUSIONS AND RELEVANCE

In a large-scale international population of HIV-positive individuals, volumes of structures in the limbic system were consistently associated with current plasma markers. Our findings extend beyond the classically implicated regions of the basal ganglia and may represent a generalizable brain signature of HIV infection in the cART era.

Progressive brain atrophy in chronically infected and treated HIV+ individuals

Growing evidence points to persistent neurological injury in chronic HIV infection. It remains unclear whether chronically HIV-infected individuals on combined antiretroviral therapy (cART) develop progressive brain injury and impaired neurocognitive function despite successful viral suppression and immunological restoration. In a longitudinal neuroimaging study for the HIV Neuroimaging Consortium (HIVNC), we used tensor-based morphometry to map the annual rate of change of regional brain volumes (mean time interval 1.0 ± 0.5 yrs), in 155 chronically infected and treated HIV+ participants (mean age 48.0 ± 8.9 years; 83.9% male) . We tested for associations between rates of brain tissue loss and clinical measures of infection severity (nadir or baseline CD4+ cell count and baseline HIV plasma RNA concentration), HIV duration, cART CNS penetration-effectiveness scores, age, as well as change in AIDS Dementia Complex stage. We found significant brain tissue loss across HIV+ participants, including those neuro-asymptomatic with undetectable viral loads, largely localized to subcortical regions. Measures of disease severity, age, and neurocognitive decline were associated with greater atrophy. Chronically HIV-infected and treated individuals may undergo progressive brain tissue loss despite stable and effective cART, which may contribute to neurocognitive decline. Understanding neurological complications of chronic infection and identifying factors associated with atrophy may help inform strategies to maintain brain health in people living with HIV.

A Re-Emerging Ancient Disease: A Case Report

There have been repeated outbreaks of leptospirosis reported all over the world. Being one of the largest cities in the world, Hong Kong is no exception. We report a local case involved in an outbreak of the disease with a typical route of acquisition but rare complications. A brief account on the epidemiology of both Hong Kong and Southern China is given. Discussions on the pathophysiology of the disease and its complications are also presented.

Evaluation of the molecular Xpert Xpress Flu/RSV assay vs. Alere i Influenza A & B assay for rapid detection of influenza viruses

A new FDA-approved Xpert Xpress Flu/RSV assay has been released for rapid influenza virus detection. We collected 134 nasopharyngeal specimens to compare the diagnostic performance of the Xpert assay and the Alere i Influenza A & B assay for influenza A and B virus detection. The Xpert assay demonstrated 100% and 96.3% sensitivity to influenza A and influenza B virus respectively. Its specificity was 100% for both viruses. The Alere i assay demonstrated slightly lower sensitivity but similar specificity to the Xpert Xpress assay. Although the Xpert assay (30 min) required longer processing time than the Alere assay (15 min), the handling procedure of the Alere assay was more complicated than the Xpert assay. As the GenXpert system has higher throughput than the Alere system, it is more suitable for hospital clinical laboratories. Overall, the new Xpert Xpress Flu/RSV assay is a reliable and useful tool for rapid influenza detection.

Mediastinal mature teratoma in a child- A case report

Mediastinal teratoma is an infrequent germ cell tumour and comprises of 1 to 5% of all mediastinal tumours. We report a case of mediastinal mature teratoma in a 12 year old boy who presented to us with persistent non-productive cough, fever and dyspnoea for the past 7 months. Computed tomographic scan of thorax revealed a large anterior mediastinal mass measuring 11.2x9.9x14cm with calcification within. He subsequently underwent a median sternotomy with left subcostal extension (L-incision) and excision of tumour. Histopathology of the tumour revealed a mature cystic teratoma. We would like to report a case of successful surgical management of a large mediastinal mature teratoma in a child.

A young patient with history of Kawasaki disease presenting with triple vessel disease

Kawasaki disease is primarily a condition that affects young children and it is associated with cardiac morbidity and mortality. This disease has been known to cause coronary artery aneurysms which occurs as a sequelae of vasculitis. The progression of triple vessel disease in adult which results from cardiac complications from Kawasaki disease is rare. We report a case of a young man with history of Kawasaki disease at infancy presenting with triple vessel disease requiring cardiac bypass surgery at the age of 20 years old.

Unusual traumatic triceps tendon avulsion rupture: a word of caution

Triceps tendon rupture is a rare condition. The usual mechanism of injury is a fall on an outstretched hand, although direct contact injuries have also been reported to cause this injury. A 67-year-old woman presented with injuries caused by direct impact to her right elbow after a fall. X-rays of the elbow demonstrated the cardinal clinical 'gap' and 'flake' signs. It is necessary to be aware of this injury and perform a careful examination at the time of the initial presentation, as the signs of this injury are usually subtle. Most reported primary repairs have been performed with non-absorbable transosseous sutures. In this case report, we show how using suture anchors for reattachment is a technically feasible alternative operative method providing a good surgical outcome.

Evaluation of an in-house genotyping resistance test for HIV-1 drug resistance interpretation and genotyping

INTRODUCTION

The human immunodeficiency virus type 1 (HIV-1) genotyping resistance test (GRT) has been considered essential for HIV-1 drug resistance monitoring. However, it is not commonly used in some developing countries in Asia and Africa due to its high running cost.

OBJECTIVE

This study aims to evaluate a new low-cost in-house GRT for both subtype B and non-B HIV-1.

STUDY DESIGN

The in-house GRT sequenced the entire protease and 410 codons of reverse transcriptase (RT) in the pol gene. Its performance on drug resistance interpretation was evaluated against the FDA-approved ViroSeq HIV-1 Genotyping System. Particularly, a panel of 235 plasma samples from 205 HIV-1-infected patients in Hong Kong was investigated. The HIV-1 drug resistance-related mutations detected by the two systems were compared. The HIV-1 subtypes were analyzed through the REGA HIV-1 Genotyping Tool and env phylogenetic analysis.

RESULTS

Among the 235 samples, 229 (97.4%) were successfully amplified by both in-house and ViroSeq systems. All PCR-negative samples harbored viral RNA at <400 copies/mL. The in-house and ViroSeq system showed identical drug resistance-related mutation patterns in 216 out of 229 samples (94.3%). The REGA pol genotyping results showed 93.9% (215/229) concordance with the env phylogenetic results including HIV-1 subtype A1, B, C, D, G, CRF01_AE, CRF02_AG, CRF06_cpx, CRF07_BC, CRF08_BC, CRF15_01B and other recombinant strains. The cost of running the in-house GRT is only 25% of that for the commercial system, thus making it suitable for the developing countries in Asia and Africa.

CONCLUSIONS

Overall, our in-house GRT provided comparable results to those of the commercial ViroSeq genotyping system on diversified HIV-1 subtypes at a more affordable price which make it suitable for HIV-1 monitoring in developing countries.

Crystal arthropathy of the lumbar spine: a report of 4 cases

Gout or pseudogout, caused by deposition of crystals, rarely affects the spine. We report 4 cases with gout or pseudogout in the lumbar spine. Two had cauda equina syndrome and another 2 had spinal stenosis. To avoid unnecessary surgery, this should be considered in the differential diagnosis when treating patients with histories of gout or pseudogout for spinal problems.

Evaluation of NucliSens EasyQ™ HIV-1 assay for quantification of HIV-1 subtypes prevalent in South-east Asia

BACKGROUND

Monitoring anti-retroviral therapy requires that viral load assays for human immunodeficiency virus type 1 (HIV-1) be applicable to diverse HIV-1 subtypes.

OBJECTIVES

To evaluate NucliSens EasyQ HIV-1 assay for quantitation of common HIV-1 subtypes prevalent in South-east Asia.

STUDY DESIGN

One hundred and nineteen plasma samples collected in Hong Kong and Cambodia were used to compare the performance of NucliSens EasyQ HIV-1 and COBAS Amplicor HIV-1 Monitor version 1.5 assays. Viral RNA extracted from the NucliSens MiniMAG was also used for HIV-1 subtyping.

RESULTS

Performance of NucliSens EasyQ correlated well with COBAS Amplicor (r=0.777, p<0.001) and the small mean difference (0.0462log(10)IU/mL) obtained in the Bland and Altman model indicated good agreement between two assays. The NucliSens EasyQ assay demonstrated a 95% sensitivity at 500IU/mL and 100% specificity. Reproducibility of this assay was within log(10)2-4IU/mL and had a coefficient of variation between 2.3% and 10.4%. Among the 109 specimens included in the analysis, HIV-1 subtyping identified 64 CRF01_AE, 38 subtype B, 3 subtype C, 3 CRF07_BC and 1 subtype G viruses.

CONCLUSIONS

Performance of NucliSens EasyQ was comparable to COBAS Amplicor for HIV-1 viral load monitoring. RNA extracts from NucliSens MiniMAG could be used for HIV-1 viral load monitoring, subtyping and drug resistance mutations detection. Our findings highlight the versatility of both NucliSens EasyQ and COBAS Amplicor in monitoring prevalent subtypes and rare circulating recombinant forms (CRFs) in the South-east Asia region.

Clinical utility of genotyping resistance test on determining the mutation patterns in HIV-1 CRF01_AE and subtype B patients receiving antiretroviral therapy in Hong Kong

BACKGROUND

HIV-1 genotypic resistance test (GRT) has been widely used to monitor HIV infection but only few reports revealed the mutation patterns of non-B HIV-1 subtypes.

OBJECTIVE

To evaluate the concordance of GRT and clinical treatment outcomes on different HIV-1 subtypes and monitor the mutation patterns and frequencies.

STUDY DESIGN

Pre- and post-treatment plasma samples from 123 patients (39 treatment naïve and 84 treatment experienced) were tested by ViroSeq HIV-1 Genotyping System followed by analysis using the Stanford HIV database. The mutation patterns and frequencies developed in the pol gene were compared among subtypes.

RESULTS

HIV-1 subtypes among patients in Hong Kong were mainly subtype B and CRF01_AE. Primary mutation was not detected among all pre-treatment samples. For post-treatment samples, primary mutations were only detected in the treatment failure group. The mutation patterns and frequencies were similar between CRF01_AE and subtype B viruses. However, the frequencies of L74V/I and K103N in the reverse transcriptase region were different between CRF01_AE and subtype B viruses. VirtualPhenotype was unable to analyze an in-frame insertion of arginine and isoleucine at protease codon 35 of one CRF01_AE isolate.

CONCLUSIONS

This is the first report to demonstrate the high degree of concordance of longitudinal genotyping data and clinical treatment outcome in patients harboring different HIV-1 subtypes. Our findings shed light to the emergence of resistance mutations and its testing in CRF01_AE, which is relevant to other prevailing places in Asia.

Clinical evaluation of real-time PCR assays for rapid diagnosis of SARS coronavirus during outbreak and post-epidemic periods

BACKGROUND

The protocols of WHO network laboratories facilitated development of rapid diagnosis for SARS coronavirus (CoV) using reverse transcription (RT)-PCR assays. However, several reports have shown that conventional and real-time PCR assays were very specific for SARS CoV but lack sensitivity depending on the assay, specimen, and time course of disease.

OBJECTIVE

To evaluate an automatic nucleic acid extraction system and two standardized real-time PCR assays for rapid diagnosis of SARS CoV during outbreak and post-epidemic periods in Hong Kong.

STUDY DESIGN

Specimens from clinically suspected SARS patients collected during outbreak and post-epidemic periods were tested by an automatic nucleic acid extraction system followed by our first generation conventional RT-PCR and two standardized real-time PCR assays (Artus GmbH, Germany and Roche Diagnostics, Germany). Paired serum samples were assayed for increasing titer against SARS CoV.

RESULTS

In the SARS epidemic, Artus and Roche PCR assays exhibited sensitivities of 87% and 85% for respiratory specimens (n = 64), 91% and 88% for stool (n = 44), and 82% for urine (n = 29). A specificity of 100% was exhibited by both PCR assays except Artus attained only a 92% specificity for stool. For post-epidemic period, no SARS CoV was identified among 56 respiratory specimens by all PCR assays. Inhibitors to PCR assays were detected at an average rate of 7-8% among 202 clinical specimens.

CONCLUSION

This study highlights the high throughput and performance of automatic RNA extraction in coordination with standardized real-time PCR assays suitable for large-scale routine diagnosis in case of future SARS epidemic. As no SARS CoV was detected among specimens collected during post-epidemic period, the positive predictive value of real-time PCR assays for detection of SARS CoV during low epidemic requires further evaluation.

Estrogen treatment induces elevated expression of HMG1 in MCF-7 cells

The high mobility group (HMG) 1 protein is a highly conserved and ubiquitous chromosomal protein found enriched in active chromatin. In this study, we have investigated the effect of estrogen on the expression of the human high mobility group protein HMG1 gene and found that the HMG1 mRNA level in MCF-7 cells was sharply increased 2.5-fold after 30 min of estrogen treatment. Under continuous estrogen treatment, the HMG1 mRNA level decreased to a 1.5 times that of the basal level at 90 min and remained at this elevated level under estrogen treatment for up to 24 h. These results support the recent finding by Verrier et al. (C.S. Verrier, 1997, Mol. Endocrinol. 11, 1009-1019) that HMG1 promotes the binding of the estrogen receptor to the estrogen response element and further reinforce our believe that HMG1 plays a significant role in estrogen-induced gene expression.

Improved heterologous expression of the white-rot fungal ligninase H8 by crossover linker mutagenesis

Using the crossover-linker mutagenesis method, the 5' noncoding region of the lambda ML-1 cDNA, which encodes the ligninase H8 isozyme of the white-rot fungus, Phanerochaete chrysosporium, was deleted with the simultaneous insertion of the putative Spodoptera frugiperda ribosome-binding sequence (RBS) (TATAAAT) directly in front of the translation-initiation codon of this gene. A recombinant baculovirus, pVL-Mu-H8, carrying the ligninase-H8 gene was successfully constructed, as determined by both sequence analysis and dot blot hybridization. A more than 18-fold increase in the expression of ligninase H8, compared to the previous pEV11-1A.3 recombinant baculovirus, was detected in the Sf-21 insect cells. This enzyme was detected within 3 d postinfection and was biologically active, capable of oxidizing the model lignin compound, veratryl alcohol. The molecular weight of the overexpressed 42 kD protein was similar to that of the native fungal ligninase-H8 isozyme and it also reacted specifically with the anti-H8 monoclonal antibody (MAb 2D4.9) in Western blot analysis.

The gene for the human architectural transcription factor HMGI-C consists of five exons each coding for a distinct functional element

The gene on chromosome 12 coding for the human protein HMGI-C has been cloned and partially sequenced. It consists of five exons, the first and last of which include long untranslated regions. The 5' UTR includes a (CA/T)n tract and a polymorphic (CT)n tract. Exons II, III and IV (87, 51 and 33 bp) are dispersed over > 30 kb. Exons I-III separately encode the three basic DNA binding domains ('A-T hooks'), exon IV encodes an 11 amino acid sequence characteristic of HMGI-C and absent from the human HMGI(Y) gene [Friedmann, M., Holth, L. T., Zoghbi, H. Y. and Reeves, R. (1993) Nucleic Acids Res., 21, 4259-4267], whilst exon V encodes the acidic C-terminal domain, which is subject to multiple phosphorylation. The HMGI-C gene is thus a striking example of the separation of functional protein elements into different coding exons.

Interaction of estrogen-nitrosourea conjugates with the estrogen receptor in rat uterus

Several estrogen-nitrosourea conjugates have been synthesized with the aim of producing more selective cytotoxic agents. The conjugates were shown to compete with estradiol for binding to cytosolic estrogen receptor in rat uterus; the relative binding affinities for N-(2-chloroethyl)-N'-(3,17 beta-dihydroxyestra-1,3,5(10)-trien-17 alpha-yl)methyl-N-nitrosourea (17 alpha-CNU), N-(2-chloroethyl)-N'-(3-hydroxyestra-1,3,5(10)-trien-17 beta-yl)-N-nitrosourea (17 beta-CNU), and N-(2-chloroethyl)-N'-2,3-di(p-hydroxyphenyl)-pentanyl-N-nitrosoure a (HEX-CNU) were 2, 0.4, and 0.2, respectively, using a binding affinity of 100 for estradiol. In the ligand exchange assay, cytosolic receptors preloaded with 17 alpha-CNU and HEX-CNU were found to lose some of their estradiol (E2) binding sites, suggesting that binding to estrogen receptor (ER) may be irreversible. An increase of nuclear accumulation of ER was observed in the presence of 17 alpha-CNU and HEX-CNU. In the rat system, even at a 10,000-fold excess, these two agents failed to show any antagonism of the uterotrophic effect of E2 in vivo. The low binding affinity and instability of these conjugates may account for their lack of antiestrogen activity. On the other hand, 17 alpha-CNU at 100 or 1000 micrograms/day and HEX-CNU at 1000 micrograms/day demonstrated significant uterotrophic activity. This study did not resolve whether the stimulation of uterine growth was due to the parent estrogen-nitrosourea conjugate or to decomposition and/or metabolic products.

Membrane transport changes in an adriamycin-resistant murine leukemia cell line and in its sensitive parental cell line

Multidrug resistance in cancer chemotherapy occurs when cells develop resistance towards structurally and functionally unrelated drugs. It is speculated that alteration of some fundamental process(es) in the cells leads to the development of multidrug resistance. The sodium pump activity of murine leukemia cell lines P388/S (sensitive) and P388/ADR (resistant) was measured and found to be different in the two cell lines. The rate of sodium pumping, i.e., the ouabain-sensitive rubidium uptake, was consistently lower in the resistant cells compared to their parental controls. Uptake of adriamycin was lower in the resistant cells. Depolarizing the cells with potassium chloride or by inhibiting the pump with ouabain increased the adriamycin uptake in the sensitive cells but not in the resistant cells. Adriamycin did not have any acute effects on the sodium pump activity. It is concluded that the development of drug resistance in cell line P388 is associated with a decrease in sodium pump activity and a lack of depolarization-induced adriamycin uptake; these processes may be causally linked via alterations in cytosolic calcium concentration.

Role of transforming growth factor-beta in the development of the mouse embryo

Using immunohistochemical methods, we have investigated the role of transforming growth factor-beta (TGF-beta) in the development of the mouse embryo. For detection of TGF-beta in 11-18-d-old embryos, we have used a polyclonal antibody specific for TGF-beta type 1 and the peroxidase-antiperoxidase technique. Staining of TGF-beta is closely associated with mesenchyme per se or with tissues derived from mesenchyme, such as connective tissue, cartilage, and bone. TGF-beta is conspicuous in tissues derived from neural crest mesenchyme, such as the palate, larynx, facial mesenchyme, nasal sinuses, meninges, and teeth. Staining of all of these tissues is greatest during periods of morphogenesis. In many instances, intense staining is seen in mesenchyme when critical interactions with adjacent epithelium occur, as in the development of hair follicles, teeth, and the submandibular gland. Marked staining is also seen when remodeling of mesenchyme or mesoderm occurs, as during formation of digits from limb buds, formation of the palate, and formation of the heart valves. The presence of TGF-beta is often coupled with pronounced angiogenic activity. The histochemical results are discussed in terms of the known biochemical actions of TGF-beta, especially its ability to control both synthesis and degradation of both structural and adhesion molecules of the extracellular matrix.

Estrogen receptor-binding affinity and cytotoxic activity of three new estrogen-nitrosourea conjugates in human breast cancer cell lines in vitro

The hypothesis that more selective antitumor activity may be achieved by cytotoxic agents which selectively bind to estrogen receptors (ER) in human cancer cells was tested. We have synthesized three nitrosourea derivatives of estradiol or hexestrol, and compared the ER binding affinity and cytotoxic activity of these compounds against ER-positive and -negative breast cancer cell lines in vitro. Specific binding to ER in the cytosol of MCF-7 human breast cancer cells was demonstrated in these conjugates: 17 alpha-CNU greater than 17 beta-CNU greater than HEX-CNU greater than lomustine (CCNU). The order of cytotoxicity of these derivatives against human breast cancer cells appeared to correlate with their binding affinity to ER. All three estrogen nitrosourea conjugates were more cytotoxic than CCNU, a clinically useful antitumor nitrosourea which does not bind to ER. The contribution of the estrogen moiety to the cytotoxicity of 17 alpha-CNU was demonstrated by the greater activity of the conjugate than that of a combination of estrogen and CCNU. However, cytotoxicity of these compounds against the receptor-positive MCF-7 and receptor-negative Evsa-T human breast cancer cell lines was similar. The latter finding suggested that cytotoxicity of these conjugates may not be mediated through ER. The difference in stability of these nitrosourea conjugates in aqueous buffer may partly explain their differences in cytotoxicity.

Development and characterization of monoclonal antibodies to bovine brain calcineurin

Three monoclonal antibodies (MAb's) against bovine brain calcineurin, a Ca++-calmodulin dependent phosphatase, have been developed and characterized. Among these antibodies, two are alpha-subunit (60,000 Mr) specific and one is beta-subunit (19,000 Mr) specific. These antibodies also cross-react with similar proteins obtained from brains of human, rat and mouse. The methodology for raising these antibodies and their properties are described.

Tamoxifen is a calmodulin antagonist in the activation of cAMP phosphodiesterase

The mechanism of action of tamoxifen, a triphenylethylene antiestrogen with antitumor activity, has not been fully established. In this paper, we present evidence that tamoxifen is an antagonist of calmodulin, a major cellular calcium receptor and calcium dependent regulator of many cellular processes. Our data showed that tamoxifen inhibited the activation of phosphodiesterase by calmodulin. This inhibition could be overcome by an increase in calmodulin concentration. Kinetic analysis demonstrated that tamoxifen is a competitive inhibitor of calmodulin in the activation of this enzyme. It could be speculated that the antagonism of calmodulin by tamoxifen may be one of the mechanisms responsible for its pharmacological actions.

A monoclonal antibody showing cross-reactivity toward three calmodulin-dependent enzymes

The spleen cells of a Balb/c mouse immunized with purified bovine calmodulin-dependent cyclic nucleotide phosphodiesterase were fused with nonsecreting mouse myeloma cells (P3-X63-Ag8-653). Antibody producing hybridomas were screened by the enzyme-linked immunosorbent assay using purified phosphodiesterase as the antigen. One monoclonal cell line, CR-B1, was found to produce antibodies which showed positive enzyme-linked immunosorbent assay reactions with bovine brain calcineurin and rabbit muscle phosphorylase kinase in addition to phosphodiesterase. The antibody was purified and characterized. It was shown to immunoprecipitate the calmodulin (CaM)-dependent phosphodiesterase and phosphorylase kinase activities but not those of CaM itself, CaM-independent phosphodiesterase and the catalytic unit of cAMP-dependent protein kinase. The immunoprecipitation of phosphodiesterase could be inhibited by calcineurin and phosphorylase kinase. These results suggest that the antibody interacts at a common site on these calmodulin-dependent proteins. The antigenic determinant in phosphodiesterase does not appear to reside in the calmodulin-binding domain of the enzyme since the antibody and phosphodiesterase interaction is not inhibited by calmodulin, and the calmodulin activation of phosphodiesterase is not affected by CR-B1 antibody. It is therefore suggested that the structural similarity among the three calmodulin-dependent proteins extends beyond the calmodulin-binding domains.

On the mechanism of interaction between calmodulin and calmodulin-dependent proteins

Molecular and kinetic studies of the interaction between calmodulin and calmodulin-dependent proteins have been reviewed. Several calmodulin-dependent proteins have been purified to homogeneity and characterized in terms of subunit structure in recent years. The results indicate that these proteins do not contain a common subunit as the basis of calmodulin binding. A monoclonal antibody capable of interacting with several calmodulin-dependent proteins has been obtained, suggesting that these proteins contain common structure. It seems that hybridoma technology may be used for probing calmodulin-binding domains in the calmodulin-dependent proteins. Using a fluorescent-labelled cyclic nucleotide phosphodiesterase, the interaction between calmodulin and the enzyme in the absence of Ca2+ can be demonstrated, and the equilibrium constant of the reaction can be determined. The study further defines the multiple interactions in the activation of the cyclic nucleotide phosphodiesterase by Ca2+ and calmodulin. Previous kinetic results along with the present results are summarized and used to elucidate the regulatory significance of the multiple Ca2+-binding of calmodulin.

Uptake and decomposition of chlorozotocin in L5178Y lymphoblasts in vitro

Uptake and metabolism of 2-[3-(2-chloroethyl)-3-nitrosoureido]-D-glucopyranose (chlorozotocin) by L5178Y lymphoblasts in vitro was investigated, using both glucose- and chloroethyl-labeled chlorozotocin. A time course of uptake of total radioactivity revealed a greater cell/medium distribution ratio of activity in cells treated with chloroethyl-labeled chlorozotocin compared to cells treated with the glucose-labeled compound. Thin-layer chromatographic analysis showed that uptake of intact chlorozotocin was identical in cells treated with either glucose- or chloroethyl-labeled drug and that the cell/medium distribution ratio never exceeded unity. Accumulation of 14C-chlorozotocin was not inhibited by an excess of unlabeled chlorozotocin, the structural analogs glucose and glucosamine, or several metabolic inhibitors or by sodium ion depletion. These observations, together with the relatively low temperature quotient for the uptake process, suggested that chlorozotocin uptake occurs by passive diffusion. In cells treated with glucose-labeled chlorozotocin, a bicyclic urethan derivative and polar metabolites soluble in trichloroacetic acid were formed. In cells exposed to chloroethyl-labeled drug, nonpolar as well as polar metabolites were noted. Formation of metabolites from the glucose moiety was impeded by the presence of an excess of unlabeled chlorozotocin, the structural analogs glucose and glucosamine, the glucose transport inhibitors phlorizin and phloretin, the metabolic inhibitor m-chlorophenyl carbonyl cyanide hydrazone and by sodium depletion. Appearance of metabolites arising from the chloroethyl moiety was also blocked by the presence of m-chlorophenyl carbonyl cyanide hydrazone and by sodium ion depletion. These results suggested that metabolism of chlorozotocin in L51789Y lymphoblasts appears to be enzyme mediated.

Active carrier-mediated transport of melphalan by two separate amino acid transport systems in LPC-1 plasmacytoma cells in vitro

Previous studies have shown that uptake of several alkylating agents occurs by independent transport mechanisms. Uptake of one of these agents, the phenylalanine derivative of nitrogen mustard (melphalan), has been investigated in LPC-1 plasmacytoma cells in vitro. Evidence suggesting that melphalan uptake is an active process is that uptake of free intact melphalan proceeds "uphill" against a concentration gradient, is temperature- and sodium-dependent, and is inhibited by several metabolic antagonists. Other findings supporting the concept that melphalan uptake is carrier-mediated is that uptake follows biphasic Michaelis-Menten kinetics, is chemically specific, and is mediated by at least two separate amino acid transport systems. Uptake by one system was sensitive to DL-beta-2-aminobicyclo[2,2,1]-heptane-2-carboxylic acid, was sodium-independent, and appeared to be mediated by system L. The second unassigned system was characterized by sodium dependence, insensitivity to 2-aminoisobutyric acid and 2-(methylamino)isobutyric acid, and was inhibited by alanine, serine, cysteine, and other amino acids.

Synthesis of steroidal nitrosoureas with antitumor activity

Four steroidal nitrosoureas with structures which may permit specific binding to estrogen receptor were synthesized. Inhibitory activity was observed against the growth of the DMBA-induced transplantable rat mammary tumor 13762.

Synthesis of 1alpha-hydroxyergocalciferol

A synthesis of 1alpha-hydroxyergocalciferol (1alpha-hydroxyvitamin D2, a potent analog of vitamin D2, is described. The preparation route involves conversion of ergosterol in two steps (60%) to the known ergosta-4, 6, 22-trien-3-one and dehydrogenation of the triene with SeO2 to ergosta-1,4,6,22-tetraen-3-one (30%). Epoxidation of the tetraenone to the corresponding 1alpha, 2alpha-epoxide followed by Li/NH3 reduction gave ergosta-5,22-diene-1alpha, 3beta-diol in 26% yield from the tetranone. After conversion to the corresponding diacetate and allylic bromination/dehydrobromination 1alpha-acetoxyergosteryl acetate was obtained. Irradiation of this intermediate gave the previtamin which was converted to the new vitamin analog by thermal equilibration and hydrolysis of the acetates. Charcteristic uv, nmr and mass spectral patterns confirmed the structure of the product.

Evidence for carrier-mediated transport of melphalan by L5178Y lymphoblasts in vitro

Mechanism of transport of the alkylating agent [14C]melphalan was investigated in L5178Y lymphoblasts in vitro. A time course of melphalan uptake was approximately linear for 5 to 10 min and thereafter entered a plateau region. Evidence that unidirectional influx of melphalan is carrier mediated was that uptake obeyed simple Michaelis-Menten kinetics, that it demonstrated chemical specificity, and that the cell/medium distribution ratio of drug decreased with increasing extracellular drug concentration. The kinetic parameters for melphalan transport consisted of a Km (mean +/- S.E.) of 1.53 +/- 0.18 X 10(-4) M and a transport capacity (Vmax) of 3.48 +/- 0.31 X 10(-17) mole/min/cell. Findings suggesting that transport was at least in part energy dependent and not simply a passive process were that drug uptake was temperature sensitive and sodium dependent. Analysis of cell sap constituents indicated the presence of intact drug within the cell. The percentage of radioactivity (mean +/- S.D.) found in the cell sap fraction was 95.8 +/- 2.2% of total cell activity, and 92.6 +/- 4.1% of this was trichloroacetic acid soluble. Thin-layer chromatography of the cell sap fraction and medium each revealed that the majority of radioactivity migrated as a single peak with an RF value identical with that obtained for free drug. The alkylating potential of intact drug complicated interpretation of the finding of apparent uphill transport against a concentration gradient. This observation, together with the relatively low cell-medium ratio (mean +/- S.D.) of 3.07 +/- 1.07, favors the concept that melphalan transport occurs by a facilitated diffusion process, although an active transport system has not been entirely excluded. The relative insensitivity of melphalan uptake to a wide range of metabolic inhibitors also suggests that transport is by a facilitated diffusion mechanism rather than an active process. Other alkylating agents and several amino acids including the L and D isomers of phenylalanine did not inhibit melphalan transport; thus a native substrate was not identified for the melphalan carrier and transport was by a mechanism separate from that of other alkylating agents.

Structural analogs of 1alpha,25-dihydroxycholecalciferol: preparation and biological assay of 1alpha-hydroxypregnacalciferol

The synthesis of 1alpha-hydroxypregnacalciferol, a side chain analog of 1alpha,25-dihydroxycholecalciferol (1alpha,25-dihydroxyvitamin D3), is described. Pregnenolone acetate was converted in five steps to 5-pregnen-1alpha,3beta-diol. Conversion of the diol to pregna-5,7-diene-1alpha,3beta diol diacetate followed by ultraviolet irradiation gave the corresponding previtamin derivative. Thermal isomerization, hydrolysis and chromatography then furnished the desired analog, 1alpha-hydroxypregnacalciferol. The compound was tested in vivo for its effect on intestinal calcium transport, serum calcium and phosphate levels and bone calcification, and in vitro for its effect on bone resorption. When given to intact rats, either as a single dose or in repeated daily doses, the analog even at high dose levels, exhibited no biological activity. The compound stimulated bone resorption in vitro, but only at high concentrations.

Synthesis and biological activity of 25xi,26-dihydroxycholecalciferol

25xi,26-Dihydroxycholecalciferol (25xi,26-dihydroxyvitamin D3), a metabolite of vitamin D3 preferentially active on intestine has been synthesized. This compound was prepared by converting 3beta-hydroxy-27-norcholest-5-en-25-one to 25xi,26-epoxy-5-cholesten--3beta-ol and base-catalyzed hydrolysis of the latter to 5-cholestene-3beta,25xi,26-triol; allylic bromination of the corresponding triacetate, and dehydrobromination gave the required 5,7-diene which yielded the vitamin derivative upon photolysis (Figure 3). The synthetic product shows the same activity pattern as the natural metabolite: at dose levels of 0.25 mug, the compound stimulates intestinal calcium transport, but has no effect on bone calcium mobilization in rats maintained on a vitamin D-deficient, low calcium diet. Higher doses (2.5 mug) elicit a more pronounced intestinal calcium transport response, but also have no significant effect on the bone mobilization system. The compound exhibits no biologial activity in nephrectomized animals.

1alpha-Hydroxyvitamin D2: a potent synthetic analog of vitamin D2

A hydroxy analog of vitamin D(2), 1alpha-hydroxyvitamin D(2), has been synthesized and tested for biological activity. This vitamin derivative is active in stimulating intestinal calcium transport and bone calcium mobilization in the rat and exhibits antirachitic activity. Its biopotency is comparable to that of the corresponding vitamin D(3) analog, 1alpha-hydroxyvitamin D(3).