Biomedical subjects

D Feldman

Publications and source records attributed to D Feldman.

At least 109 records · Page 6Linked to original sources

PubMed1996

Parathyroid hormone--related protein (PTHrP) is an epidermal growth factor-regulated secretory product of human prostatic epithelial cells.

Parathyroid hormone-related protein (PTHrP) has previously been shown to be expressed in human prostatic tissue and in prostatic cancer cell lines. In the present study, PTHrP immunoreactivity was detected in the glandular epithelium of normal prostate and benign prostatic hyperplasia (BPH), as well as in prostatic adenocarcinoma (CaP). Epithelial cell cultures derived from normal, BPH, and CaP tissues were also stained by antibodies against PTHrP, and northern analysis revealed multiple transcripts of PTHrP in the cellular RNA. PTHrP (1-34) was measurable by radioimmunoassay (RIA) in media conditioned by the prostatic epithelial cell cultures, and PTHrP accumulated in conditioned media during a 72 hr time course. Addition of complete growth medium to starved cells resulted in increased PTHrP mRNA levels by 1 hr, with maximal stimulation at 8-24 hr. Several individual factors contained in the complete growth medium were tested for their ability to regulate PTHrP expression. Epidermal growth factor (EGF) was the major inducer of PTHrP expression, while cholera toxin, bovine pituitary extract, hydrocortisone, and insulin had minimal or no effect on PTHrP transcript levels. Since each of these factors is growth stimulatory, the unique ability of EGF to induce PTHrP is apparently unrelated to mitogenicity. 1,25-Dihydroxyvitamin D3[1,25(OH)2D3], an inhibitor of PTHrP expression in several other cell types, had no effect on steady-state levels of PTHrP mRNA expressed by epithelial cells in complete growth medium, although prostate cells have vitamin D receptors and are responsive to 1,25(OH)2D3 in other ways. Our results indicate that PTHrP expression is not confined to the neuroendocrine cells of the human prostate and that our culture system can be used as a model to investigate the role of PTHrP in the prostate.

Adenocarcinoma↗

PubMed1996

The presence of a polymorphism at the translation initiation site of the vitamin D receptor gene is associated with low bone mineral density in postmenopausal Mexican-American women.

We examined the association of bone mineral density (BMD) with a polymorphism in the gene encoding the vitamin D receptor (VDR) that causes a change in the predicted protein sequence. The polymorphism results from a C-to-T transition and creates an initiation codon (ATG) three codons proximal to a downstream start site. The polymorphism can be defined by a restriction fragment length polymorphism (RFLP) using the restriction endonuclease FokI. The presence of a FokI site, designated f, allows protein translation to initiate from the first ATG. The allele lacking the site (designated F), initiates from a second ATG site. Thus, translation products from these alleles are predicted to differ by three amino acids with the f variant elongated. In a group of 100 postmenopausal Mexican-American Caucasian women, subjects with the ff genotype (15% of the study population) had a 12.8% lower BMD at the lumbar spine than FF subjects (37% of the population) (p = 0.01). Heterozygote (Ff) subjects (48% of the population) had an intermediate BMD. This association between BMD and genotype was not apparent at the femoral neck or forearm. Over a 2-year follow-up period, a decrease in BMD at the femoral neck was greater in ff compared with FF subjects (-4.7% vs. -0.5%, p = 0.005). This trend was not apparent at the lumbar spine or forearm. There were no differences between genotype groups in measurements of 25-hydroxyvitamin D (25(OH)D), calcitriol, parathyroid hormone (PTH), osteocalcin, or urinary pyridinolines. We conclude that the FokI polymorphism of the VDR gene correlates significantly with decreased BMD at the lumbar spine and with an increased rate of bone loss at the hip in ff subjects. We emphasize that these initial data should be interpreted with caution but that the utility of this polymorphism as a genetic marker to determine BMD and osteoporosis risk warrants further study in larger populations with subjects of diverse ethnic backgrounds.

Aged↗

PubMed1996

Telling patients about the diagnosis of HIV infection.

This study used a questionnaire to examine how patients in the HIV/AIDS Clinic at a Department of Veterans Affairs hospital were told of their diagnosis, by whom, and to what degree they were given emotional and educational support. Nearly 17% of patients were informed by someone not in the health professions (often military personnel), and 27% of patients were notified in a nonprivate setting. Forty-seven percent indicated they received little or no educational support at the time of diagnosis, while 39% received little or no emotional support. Educational and emotional support for patients at the time of HIV diagnosis may be lacking.

Adult↗

PubMed1996

Primary health care physicians' treatment of psychosocial problems: implications for social work.

This study explores the extent to which primary care physicians serve as gatekeepers for the treatment of psychosocial problems and the extent to which they have contact with social workers. We also attempted to identify physician variables related to gatekeeping and amount of contact with social workers. Data from a national study of the role of primary care physicians in Israel were used. About one-third of the physicians had regular contact with social workers, one-quarter had contact less often, and about one-third almost never had contact. Variables associated with gatekeeping for psychosocial problems included having a large caseload, specializing in family medicine, practicing in a rural location, and being under age 55. Variables associated with social work contact were affiliation with the largest health maintenance organization and specialization in family medicine.

Adolescent↗

PubMed1996

An innovative CME program in cardiology for primary care practitioners.

The authors describe an innovative continuing medical education (CME) program they developed to improve the ability of community practitioners to manage common cardiology problems. The program includes an objective structured clinical examination (OSCE) with nine standardized patient (SP) stations. The SPs are trained to use checklists to assess the examinees' clinical skills, and to enter the checklist data directly into computers located within each of the examining rooms. Checklists cover the participants' knowledge of cardiology, and their interviewing, physical-examination, and counseling skills. The computer immediately generates detailed individual reports, which include a skills report, reflecting performance of core skills across all nine stations with group means for comparison, and an omissions report, listing items missed in each case for each participant and, again, comparing the results with group means. Participants review and discuss their performances and then discuss identified learning issues with a cardiologist. The cardiologist also reviews state-of-the-art diagnosis and treatment for the cases presented in the OSCE. Participants have reported having a high regard for the program and have indicated that the program has left them better prepared to deal with clinical cardiology issues.

Attitude of Health Personnel↗

PubMed1996

A novel mutation in the deoxyribonucleic acid-binding domain of the vitamin D receptor causes hereditary 1,25-dihydroxyvitamin D-resistant rickets.

Mutations in the vitamin D receptor (VDR) result in hereditary 1,25-dihydroxyvitamin D3-resistant rickets (HVDRR), an autosomal recessive disease caused by target organ resistance to the action of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. In this study, we investigated the molecular basis of HVDRR in a child from Saudi Arabia who was previously shown to be resistant to 1,25-(OH)2D3 action, but whose cultured skin fibroblasts exhibited normal [3H]1,25-(OH)2D3 binding. Using the PCR, exons 2 and 3 of the VDR gene that encode the DNA-binding region of the receptor were amplified and sequenced. A novel point mutation at nucleotide 252 in exon 2 of the VDR was identified. This missense mutation (GGC to GAC) resulted in the conversion of glycine to aspartic acid at amino acid position 46 (G46D), located at the base of the first zinc finger. This single base change was introduced into wild-type VDR complementary DNA by site-directed mutagenesis, and the mutant VDR was then expressed in COS-1 cells. The expressed mutant VDR displayed a normal binding affinity (Kd = 1.2 x 10(-10) mol/L) for [3H]1,25-(OH)2D3 as determined by Scatchard analysis. However, the mutant VDR was shown to have reduced binding affinity for DNA by DNA-cellulose chromatography. In COS-7 cells cotransfected with a vitamin D response element-chloramphenicol acetyltransferase reporter construct and the mutant VDR complementary DNA expression vector, the mutant VDR was unable to activate gene transcription in cells treated with up to 100 nmol/L 1,25-(OH)2D3. Restriction fragment length polymorphism analysis using MwoI restriction digests of exon 2 demonstrated that the affected child is homozygous for the mutation, whereas the child's father is heterozygous and a carrier of the defective allele. In conclusion, a new mutation was identified in exon 2 of the VDR gene. This mutation, which occurs in the first zinc finger of the DNA-binding domain of the receptor, blocks 1,25-(OH)2D3 action and leads to the syndrome of HVDRR.

Base Sequence↗

PubMed1995

Vitamin D and prostate cancer.

Our findings demonstrate the presence of VDR in various human prostate cancer cell lines and in primary cultures derived from normal, BPH and prostate cancer. In addition, 1,25-D induced several bioresponses in these cells including growth inhibition and PSA stimulation. Based on examples in many different malignant cells as well as our data in prostate cells, that vitamin D is anti-proliferative and promotes cellular maturation, it seem clear that vitamin D must be viewed as an important cellular modulator of growth and differentiation if addition to its classical role as regulator of calcium homeostasis. In this respect, vitamin D has the potential to have beneficial actions on various malignancies including prostate cancer. Its ultimate role in prostate cancer remains to be determined, but 1,25-D may prove useful in chemoprevention and/or differentiation therapy. We believe the data currently available provide the basis for an optimistic view on the possible use of vitamin D to treat prostate cancer in patients and that further investigation is clearly warranted to better define its potential therapeutic utility.

Calcitriol↗

PubMed1995

Detecting psychological distress among patients attending secondary health care clinics. Self-report and physician rating.

A study was conducted to determine the prevalence of psychological distress, as reported by patients and their physicians, in orthopedic, neurology, dermatology, and ophthalmology clinics; to study their accuracy in detecting psychological distress; and to determine if there is any connection among psychological distress, accuracy of detecting distress, and use of mental health and primary health care physicians' prognosis for the somatic complaints. Five hundred and fifty-six patients, ages 18-21, responded to the Psychiatric Epidemiology Research Interview Demoralization Scale (PERI-D), a measure of psychological distress, and to questions about their mental health and use of mental health and primary health services. Physicians, who were blind to patients' responses, were asked to what extent they thought the cause of patients' complaints was physical and to what extent they thought it was psychological in nature, and to prognosticate. Based on the PERI-D, about 25% of patients were distressed, this was less for females than males and varied between clinics. Based on self-reporting, about 14% of patients (males and females) were distressed. Based on physician reporting, about 17% (males less) were distressed. Physicians identified 35% of the PERI-D-distressed cases and 79% of nondistressed cases. About 66% of patients identified their distress and 83% their lack of distress. Increased use of primary health care and mental health care was related to distress. The prognosis was negatively related to distress. Based on this study, there is a need for more attention to psychological distress among secondary health care patients. Patients' ability to identify their distress suggests the importance of involving the patient in the diagnostic process. Correct detection of distress alone does not appear to decrease the use of primary medical and mental health services.

Adolescent↗

PubMed1995

Oestrogen-binding protein in Candida albicans: antibody development and cellular localization by electron immunocytochemistry.

Candida albicans, the most common fungal pathogen of humans, possesses an oestrogen (estrogen)-binding protein (EBP) that binds oestrogens with high affinity and specificity. The gene that encodes the EBP (CaEBP1) has been cloned and sequenced and shown to be structurally related to the old yellow enzyme from Saccharomyces cerevisiae. Here, we report the purification and the subcellular localization of the EBP from C. albicans. Using ion-exchange chromatography and an oestradiol affinity column, the EBP was purified from a strain of C. albicans (strain 422) which was selected because it constitutively expressed elevated levels of the binding protein. The purified protein displayed a subunit molecular mass of approximately 46 kDa when examined by denaturing gel electrophoresis, which is consistent with the size estimated from the sequence of the cloned CaEBP1 gene. An immunoaffinity column, prepared using a polyclonal antisera generated against EBP, depleted the oestrogen-binding activity from C. albicans cell extracts. Western blot analysis showed that the antisera specifically recognized the EBP from C. albicans. The antibodies also recognized the protein when the cloned CaEBP1 gene was expressed in S. cerevisiae and did not cross react with S. cerevisiae proteins. Using electron microscopy and antigen detection by immunogold staining, the EBP appeared to be primarily associated with vacuoles. However, when overexpressed in S. cerevisiae, the EBP was found diffusely throughout the cell. In conclusion, the EBP has been purified from C. albicans and antibodies generated against the protein were used to demonstrate that EBP is found associated with vacuoles in C. albicans.

Blotting, Western↗

PubMed1995

Actions of vitamin D3, analogs on human prostate cancer cell lines: comparison with 1,25-dihydroxyvitamin D3.

Data from epidemiological studies has suggested that vitamin D deficiency may promote prostate cancer, although the mechanism is not understood. We have previously demonstrated the presence of vitamin D receptors (VDR) in three human prostate carcinoma cell lines (LNCaP, PC-3, and DU-145) as well as in primary cultures of stromal and epithelial cells derived from normal and malignant prostate tissues. We have also shown that 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] can elicit an antiproliferative action in these cells. In the present study we compared the biological actions of 1,25-(OH)2D3 to those of a series of natural vitamin D3 metabolites and several synthetic analogs of vitamin D3 known to exhibit less hypercalcemic activity in vivo. In ligand binding competition experiments, we demonstrated the following order of potency in displacing [3H]1,25-(OH)2D3 from VDR: EB-1089 > 1,25-(OH)2D3 > MC-903 > 1,24,25-(OH)3D3 > 22-oxacalcitriol (OCT) > 1 alpha,25-dihydroxy-16-enecholecalciferol (Ro24-2637) > 25-hydroxyvitamin D3, with EB-1089 being approximately 2-fold more potent than the native hormone. No competitive activity was found for 25-hydroxy-16,23-diene-cholecalciferol. When compared for ability to inhibit proliferation of LNCaP cells, MC-903, EB-1089, OCT, and Ro24-2637 exhibited 4-, 3-, and 2-fold greater inhibitory activity than 1,25-(OH)2D3. Interestingly, although OCT and Ro24-2637 exhibit, respectively, 10 and 14 times lower affinity for VDR than 1,25-(OH)2D3, both compounds inhibited the proliferation of LNCaP cells with a potency greater than that of the native hormone. The relative potency of vitamin D3 metabolites and analogs to inhibit cell proliferation correlated well with the ability of these compounds to stimulate prostate-specific antigen secretion by LNCaP cells as well as with their potency to induce the 25-hydroxyvitamin D3-24-hydroxylase messenger RNA transcript in PC-3 cells. In conclusion, these results demonstrate that synthetic analogs of vitamin D3, known to exhibit reduced calcemic activity, can elicit antiproliferative effects and other biological actions in LNCaP and PC-3 cell lines. It is noteworthy that although binding to VDR is critical for 1,25-(OH)2D3 action, the analog data indicate that additional factors significantly contribute to the magnitude of the biological response. Finally, the strong antiproliferative effects of several synthetic analogs known to exhibit less calcemic activity than 1,25-(OH)2D3 suggest that these compounds potentially may be useful as an additional therapeutic option for the treatment of prostate cancer.

Binding Sites↗

PubMed1995

Regulation of 1,25-dihydroxyvitamin D3 receptors by parathyroid hormone in osteoblastic cells: role of second messenger pathways.

The regulation of vitamin D receptor (VDR) abundance in MC3T3-E1 mouse osteoblasts and UMR 106-01 rat osteosarcoma cells by rat PTH 1-34, human PTH-related protein 1-34, and agents that activate specific signal transduction pathways was studied. Treatment of these cells with forskolin (FSK) caused up-regulation of VDR, whereas treatment with phorbol esters suppressed VDR levels. PTH or PTH-related protein treatment induced a 2- to 3-fold increase in VDR, which was equivalent to that elicited by FSK in UMR 106-01 cells but less than the FSK-induced increase (approximately 8-fold) in MC3T3-E1 cells. PTH treatment of MC3T3-E1 cells resulted in an approximately 3-fold increase in VDR levels with maximum stimulation occurring at 10(-9) M PTH after 4 h of treatment. In UMR 4-7 cells, a subclone of UMR 106-01 cells that express cAMP resistance due to regulated expression of a mutant form of the type 1 regulatory subunit of the cAMP-dependent protein kinase A (PKA), the up-regulation of VDR abundance due to FSK and PTH treatment was mostly prevented. Pretreatment of MC3T3-E1 cells with staurosporine, an inhibitor of PKC, resulted in an approximately 3-fold increase in basal VDR levels but did not enhance the PTH-mediated up-regulation of VDR. Collectively, these data suggest that the increase in VDR abundance observed in these target cells is mainly due to the activation of the PKA signal transduction pathway. Treatment of UMR 106-01 cells with PTH for 4 h before exposure of the cells to 1,25-dihydroxyvitamin D3 resulted in a 2-fold increase in the induction of 25-hydroxyvitamin D3-24 hydroxylase messenger RNA. Thus, exposure of target cells to PTH augments their response to 1,25-dihydroxyvitamin D3 due to up-regulation of VDR abundance.

Animals↗

PubMed1995

Estrogens in unexpected places: possible implications for researchers and consumers.

Estrogenic activity originating in unexpected places was encountered on three occasions during an investigation of whether Saccharomyces cerevisiae synthesized estrogens. In each instance, estradiol found in the conditioned yeast culture medium originated from an exogenous source and was not synthesized by the yeast. In the first instance, yeast grown in the laboratory showed a time-dependent increase in estradiol in the conditioned medium. However, the culture medium supplement Bacto-peptone was found to contain large amounts of estrone. When added to yeast cultures in the form of YPD medium (yeast extract, Bacto-peptone, and dextrose), S. cerevisiae converted the estrone to estradiol leading to the accumulation of estradiol over time. In the second instance, commercially purchased S. cerevisiae grown in a molasses medium exhibited substantial amounts of estradiol. However, corn and beet molasses contained sufficient estrone and estradiol to account for the findings. As in the first instance, the yeast converted the estrone into estradiol. In the third instance, autoclaving culture medium in polycarbonate plastic flasks was found to cause an estrogenic substance to be added to the medium, whether yeast were present or not. It was determined that the autoclaving process leached bisphenol-A (BPA) out of the polycarbonate plastic. BPA was shown to bind to estrogen receptors and to induce estrogenic activity, including stimulation of MCF-7 breast cancer-cell proliferation and induction of the expression of progesterone receptors. The three instances highlight potential problems for investigators who might inadvertently add estrogens to experimental systems confounding their results. The BPA findings raise concerns about the possible addition of this estrogenic molecule to the food supply since polycarbonate plastic is used in myriad applications in the packaging of food and beverages. Although we are unaware of the substantial contamination of food products with BPA, we believe this possibility should be carefully investigated.

Benzhydryl Compounds↗

PubMed1995

Pain complaints and psychological distress among soldiers in specialty military medical clinics.

PURPOSE: This paper explores: (1) the relationship of pain complaints and psychological distress among orthopedic, dermatology, ophthalmology, and neurology outpatients, (2) the ability of patients with pain complaints and their physicians to detect patients' psychological distress, and (3) the connection between type of pain, prognosis as rated by physician, and patient's use of military primary health care and mental health treatment. METHOD: Five hundred fifty-six soldiers in compulsory service in the Israel Defence Forces, ages 18 to 21, responded to the PERI-D (Psychiatric Epidemiological Research Interview Demoralization Scale), a measure of psychological distress, and questions about presenting medical complaint and use of mental health and primary health services. Military specialist physicians, who were blind to patients' responses, were asked the extent to which they thought that the cause of the patients' complaints were physical or psychological and to prognosticate. RESULTS: Almost 47% of soldiers attended clinics due to pain. In descending order were limb pain (42.5%), headache (29.1%), lower-back pain (24.5%), and right arm pain (3.8%). Right arm complainers were the most distressed and the heaviest users of primary health care and got the lowest prognosis, yet the physicians did not detect any psychological distress in this group. The least distressed and lowest users of medical services were patients with limb pain. There was a positive linear relationship between psychological distress and use of primary health care. There was a negative linear relationship between distress and prognosis. The patients' ability to detect psychological distress was better than that of the physicians. Physicians tended to find more cases of psychological distress than did the PERI-D in lower-back pain and limb pain patients. Psychologically distressed headache and limb pain patients reported using significantly more primary health care than non-distressed patients with similar pain complaints. CONCLUSIONS: Special attention to psychological distress among pain complainers in military secondary health care clinics is needed. Such attention may reduce the use of primary health care and may have implications for improving prognoses.

Adolescent↗

PubMed1994

Candida albicans estrogen-binding protein gene encodes an oxidoreductase that is inhibited by estradiol.

Candida albicans, the most common fungal pathogen of humans, possesses an estrogen-binding protein (EBP) that binds mammalian estrogens with high affinity. We report here the cloning and complete nucleotide sequence of a gene encoding a C. albicans EBP. Amino acid sequences obtained from cyanogen bromide fragments of purified EBP were used to design oligonucleotide primers for PCR. An 800-bp product was amplified and used to screen a C. albicans genomic library. A clone was isolated containing an insert with an open reading frame of 1221 nt capable of encoding a protein with 407 amino acids and having a calculated molecular mass of 46,073 Da, the estimated size of EBP. The cloned gene, expressed in Escherichia coli as a lacZ fusion protein, demonstrated high-affinity binding for estradiol and a competition profile comparable to C. albicans wild-type EBP. Northern blots of C. albicans RNA revealed a single transcript of approximately 1600 nt, whereas Southern blots identified three hybridizing fragments. Computer searches of data bases showed that EBP shares a 46% amino acid identity with the old yellow enzyme, an oxidoreductase from Saccharomyces cerevisiae, but was unrelated to the human estrogen receptor as previously speculated. In addition, a 51-amino acid region of EBP is highly conserved among a group of flavoproteins including old yellow enzyme. Expressed EBP was shown to exhibit oxidoreductase activity that could be inhibited by 17 beta-estradiol in vitro. In conclusion, the EBP from C. albicans has no evident homology to the mammalian steroid receptor superfamily but appears to be a member of a recently identified family of flavoproteins.

Amino Acid Sequence↗

PubMed1994

Antiproliferative effects of 1,25-dihydroxyvitamin D3 on primary cultures of human prostatic cells.

Cultures of adult human prostatic epithelial and fibroblastic cells were established from normal, benign hyperplastic, and malignant tissues. Vitamin D receptors were detected by ligand binding of [3H]1,25-dihydroxyvitamin D3 [1,25(OH)2D3] in cytosolic extracts prepared from all types of cell cultures as well as from fresh prostatic tissues. Vitamin D receptor transcripts were demonstrated by Northern blot analysis. 1,25-(OH)2D3 inhibited the growth of epithelial cells with half-maximal inhibition at approximately 1 nM. The growth of fibroblasts was also inhibited by 1,25(OH)2D3 but to a lesser extent. This is consistent with the apparently lower level of vitamin D receptors in fibroblasts compared to epithelial cells determined by ligand binding and Northern analysis of RNA transcripts. The growth inhibition of epithelial cells by 1,25(OH)2D3 was irreversible even after a short 2-h exposure, but morphology and keratin expression were not appreciably altered by long-term exposure to the hormone. A physiological role for 1,25(OH)2D3 in the prostate is postulated, and the inhibitory effect of 1,25(OH)2D3 on cancer-derived prostate cells may provide a basis for new preventive or therapeutic strategies.

Adult↗

PubMed1994

A 13-week toxicologic and pathologic evaluation of prolonged cytochromes P450 inhibition by 1-aminobenzotriazole in male rats.

The pharmacologic, toxicologic, and microscopic effects of 100 mg/kg/day of 1-Aminobenzotriazole (ABT), a suicide substrate inhibitor of cytochromes P450, were assessed in male Sprague-Dawley rats over a 13-week period. Hepatic cytochromes P450 levels and resorufin dealkylase activity were decreased to less than 30% of control values beginning at Day 2 and from Day 8 to Day 92. These decreases were not accompanied by overt clinical toxicity, e.g., changes in body weight, food consumption, or clinical appearance, during the study. Hemoglobin, hematocrit, and erythrocyte counts were slightly decreased at 8, 29, and 92 days and were accompanied by increased spleen weights and extramedullary hematopoiesis. Additionally, mean corpuscular hemoglobin concentration, mean corpuscular volume, red cell distribution width, and mean corpuscular hemoglobin were slightly increased at 92 days. Increases in liver weights at 8, 29, and 92 days were accompanied by centrilobular hypertrophy and intracytoplasmic vacuolization consistent with lipid accumulation. Thyroid stimulating hormone (TSH) was slightly elevated and triiodothyronine and thyroxine were slightly decreased at 29 days. TSH was also slightly elevated at 8 and 92 days, and thyroid gland weights were increased at 8, 29, and 92 days with microscopic evidence of hyperplasia and hypertrophy of thyroid gland follicular cells. Increased adrenal weights and hypertrophy of the zona fascicularis of the adrenal gland were observed at 8, 29, and 92 days. Kidney weights were also increased at these assessments. Changes in the thyroid gland, the thyroid hormone profile, and the liver may reflect increased synthesis of microsomal enzymes, an effect that is sometimes difficult to demonstrate directly with suicide substrate inhibitors of cytochromes P450. In general, the effects of daily ABT administration to male rats at a dose that significantly reduces oxidative metabolism over a 13-week period were considered to be well-tolerated under controlled laboratory conditions.

Animals↗

PubMed1994

Schwann cell mitochondrial alterations in peripheral nerves of rabbits treated with 2',3'-dideoxycytidine.

2',3'-Dideoxycytidine (ddC) is a nucleoside analogue and reverse-transcriptase inhibitor that is approved for treatment of AIDS patients. A rabbit model of ddC neurotoxicity was developed to help understand the dose-limiting clinical neurotoxicity of ddC. Rabbits with a myelinopathy resulting from treatment with ddC exhibited mitochondrial alterations in Schwann cells of sciatic and tibial nerves and dorsal root ganglia. These changes were initially evident after 16 weeks of oral treatment with 35 mg/kg per day of ddC and were positively correlated with myelin pathology in individual animals. Cup-shaped mitochondria were frequently observed; when these mitochondria occurred in multiple concentric arrays or at various angles to one another, different profiles were formed depending on the plane of section. An increased number of mitochondrial cristae assumed a tubular configuration. It is suggested that the complex aggregations of mitochondria seen in this experiment are an adaptive response to altered mitochondrial function caused by treatment with ddC.

Acquired Immunodeficiency Syndrome↗

PubMed1994

Inhibition of aldosterone synthesis in rat adrenal cells by nicotine and related constituents of tobacco smoke.

Previous work has shown that nicotine and related constituents of tobacco smoke inhibit selected P450 enzymes in the glucocorticoid and sex steroid synthetic pathways. Because aldosterone synthesis is also cytochrome P450 dependent, we hypothesized a similar inhibitory action on aldosterone production. In this study we examined the effects of nicotine, anabasine (a related alkaloid), and cotinine (the major metabolite of nicotine) on in vitro aldosterone synthesis. Freshly isolated rat adrenal cells were assayed for corticosterone and aldosterone production in the basal state and after stimulation with ACTH or angiotensin-II (ANG-II). The addition of nicotine, anabasine, and cotinine in concentrations up to 100 microM did not inhibit stimulated corticosterone production. However, there was a potent dose-dependent inhibitory action of all three tobacco compounds on aldosterone production. The relative inhibitory potency was: cotinine > anabasine > nicotine. When employed at a concentration of 100 microM, the three compounds inhibited ACTH-stimulated aldosterone synthesis by 75%, 44%, and 21%, respectively. ANG-II-stimulated aldosterone synthesis was inhibited by 92%, 78%, and 62%, respectively. The plasma cotinine concentration range attained in tobacco smokers is between 1-10 microM. When tested with [3H]corticosterone and [3H]progesterone as exogenous substrates, 1-10 microM cotinine caused a significant dose-dependent inhibition of ACTH- and ANG-II-stimulated aldosterone synthesis. Cotinine substantially blocked the conversion of corticosterone to 18-hydroxycorticosterone, implicating the 18-hydroxylase or corticosterone 18-methyloxidase-I (CMO-I) step as the major site of inhibition. In summary, our results indicate that tobacco compounds cause direct and specific inhibition of aldosterone synthesis, primarily at the CMO-I step. This enzymatic blockade would be expected to result in activation of the renin-angiotensin system in vivo. We postulate that chronic stimulation of the renin-angiotensin system by this mechanism might contribute to the cardiovascular damage that occurs with long term tobacco use.

Adrenal Glands↗