Catecholamine, renin, aldosterone, and arginine vasopressin responses to lower body negative pressure and tilt in normal humans: effects of bromocriptine

We have examined the effects of the dopamine agonist bromocriptine (BEC) on the hormonal and hemodynamic response to graded lower body negative pressure (LBNP) and tilting in five normal volunteers. BEC blunted the plasma norepinephrine (NE), plasma renin activity (PRA), and aldosterone responses to both LBNP and tilting. The inhibitory effects of BEC on the plasma NE response to these maneuvers are likely mediated through presynaptic inhibition of peripheral neuronal release of NE as well as central nervous system effects of the drug. Since the PRA responses to LBNP and tilting are likely mediated through beta-adrenoreceptor stimulation, BEC probably indirectly blunts the PRA and aldosterone responses to those maneuvers through its inhibitory effects on NE secretion. BEC treatment resulted in a hypotensive response to tilting that was accompanied by a rise in plasma potassium and arginine vasopressin (AVP). No such rises in plasma potassium and AVP are observed, in the absence of BEC treatment, following graded LBNP and tilting. The rise in plasma potassium with tilting (BEC treatment) probably resulted from blunting of the NE rise. Thus, the rise in plasma NE may play an important role in preventing a rise in plasma potassium in association with LBNP and orthostatic stress. AVP levels in normal men are not responsive to unloading of cardiopulmonary and sinoaortic baroreceptors. It is only after overt hypotension is produced--as after BEC treatment--that plasma levels of AVP rise.     

Effect of short-term glucocorticoids on serum osteocalcin in healthy young men

Young healthy men were studied during brief treatment with prednisone to determine the rapidity of the effects of glucocorticoids on serum osteocalcin. Seven subjects were given 60 mg of prednisone orally at 8 a.m. on 5 consecutive days. Serum osteocalcin fell to 68% of the pretreatment level within 24 hours after the first dose was administered (p less than 0.01) and reached a nadir of 37% of baseline between 48 and 96 hours after treatment was begun (p less than 0.005). When prednisone was discontinued, serum osteocalcin returned promptly to pretreatment levels. Similar, though less marked, effects were found with lower doses of prednisone. Serum osteocalcin was not different from baseline after 5 mg of prednisone in five subjects, but after treatment of five subjects each with 10, 15, or 20 mg of prednisone, osteocalcin levels were 83%, 78%, and 74% of baseline, respectively (p less than 0.05). Serum osteocalcin levels fell rapidly with glucocorticoid administration, indicating that the effects of glucocorticoids on bone cells may be demonstrated long before clinical evidence of osteoporosis becomes apparent.     

Effect of clozapine on the sleep pattern in the rat.

The effect of clozapine on the sleep pattern in the rat was studied after a single injection (2.5--20 mg/kg) and after daily administration for 11 consecutive days (2 X 20 mg/kg/day). After a single injection clozapine significantly suppressed REM sleep in a dose-related way, leaving slow wave sleep (SWS) unchanged. Follwing chronic administration, however, clozapine exerted its most prominent effect on SWS, the enhancement of which persisted for at least 3 days after discontinuation of treatment. REM sleep decreased with the development of tolerance and in the absence of rebound phenomena. The results are discussed in the light of disturbances in brain monoamines and the tolerance these amines developed to repeated administration of clozapine.     

Effect of clonidine and yohimbine on sleep in healthy men: a double-blind,randomized, controlled trial

Objective: To study the acute effect of clonidine, an α₂-adrenoceptor agonist, and yohimbine, an α₂-adrenoceptor antagonist, on nocturnal sleep in healthy men. Setting: McGuire Veteran Affairs Medical Center, Richmond, Virginia, USA. Subjects: Eight healthy male volunteers. Methods: Each subject slept in the sleep laboratory for 2 consecutive nights on three separate sessions, at 3-week intervals. On the 2nd night of each session, the subjects received yohimbine (5.4 mg), clonidine (0.1 mg), or placebo in a double-blind, randomized, placebo-controlled, crossover design. Results: There were no apparent effects of yohimbine. In contrast, clonidine completely suppressed rapid eye movement (REM) sleep in one subject and reduced REM sleep in the remaining seven subjects. Conclusion: Our study confirms that clonidine markedly decreases REM, even at a low single dose, and supports the hypothesis of the important role of α₂-receptors in controlling REM sleep. Received: 11 August 1995/Accepted in revised form: 2 January 1996     

Development and validation of a modified comet assay to phenotypically assess nucleotide excision repair

There is an increasing need for simple and reliable approaches to phenotypically assess DNA repair capacities. Therefore, a modification of the alkaline comet assay was developed to determine the ability of human lymphocyte extracts to perform the initial steps of the nucleotide excision repair (NER) process, i.e. damage recognition and incision. Gel-embedded nucleoids from A549 cells, pre-exposed to 1 microM benzo[a]pyrene-diol-epoxide, were incubated with cell extracts from frozen or freshly isolated lymphocytes. The rate at which incisions are introduced and the subsequent increase in tail moment is indicative for the repair capacity of the extracts. Freshly prepared extracts from lymphocytes of human volunteers (n = 8) showed significant inter-individual variations in their DNA repair capacity, which correlated with the removal of bulky DNA lesions over a period of 48 h determined by (32)P-post-labelling (R(2) = 0.76, P = 0.005). Repeated measurements revealed a low inter-assay variation (11%). Storage of cell extracts for more than 3 weeks significantly reduced (up to 80%) the capacity to incise the damaged DNA as compared to freshly isolated extracts. This reduction was completely restored by addition of ATP to the extracts before use, as it is required for the incision step of NER. In contrast, extracts freshly prepared from frozen lymphocyte pellets can be used without loss of repair activity. DNA repair deficient XPA-/- and XPC-/- fibroblasts were used to further validate the assay. Although some residual capacity to incise the DNA was observed in these cells, the repair activity was restored to normal wild-type levels when a complementary mixture of both extracts (thereby restoring XPA and XPC deficiency) was used. These results demonstrate that this repair assay can be applied in molecular epidemiological studies to assess inter-individual differences in NER.     

Male menopause

Menopause is the cessation of menses caused by the age-associated decline in gonadal hormone secretion in women. Although men do not menstruate, they do have an age-associated decline in gonadal hormone secretion. This "male menopause" is associated with loss of libido, loss of muscle mass and various other undesirable effects. The underlying causes of decreased testosterone production in older men may include decreased hypothalamic gonadotropin releasing hormone (GnRH) secretion, impaired feedforward effect of luteinizing hormone (LH) on testosterone secretion and decreased testosterone release from the Leydig cells. When chronic illness is superimposed on healthy aging, there are further decrements in testosterone availability. Although a consensus has not been reached, various studies suggest that older men may benefit from testosterone supplementation. For example, testosterone supplementation to older men seems to cause increased muscle protein synthesis, increased muscle strength and decreased cholesterol. Nevertheless, if testosterone supplementation is provided, clinicians must be vigilant to detect adverse effects such as accelerated growth of prostate carcinoma.     

Immunoperoxidase detection of polycyclic aromatic hydrocarbon-DNA adducts in mouth floor and buccal mucosa cells of smokers and nonsmokers

Tobacco smoking is a major risk factor for oral cancer; mouth floor and buccal mucosa are among the most and least cancer-prone subsites, respectively, in the oral cavity. We investigated the applicability of immunohistochemistry of smoking-induced DNA adducts in oral cells for assessing the exposure to carcinogens, and estimating the risk for oral cancer. Polycyclic aromatic hydrocarbon (PAH)-DNA adducts were measured in mouth floor and buccal mucosa cells of smokers (n = 26) and nonsmokers (n = 22) by means of a semiquantitative immunoperoxidase assay. Smokers had elevated levels of PAH-DNA adducts compared to nonsmokers in their mouth floor cells (0.045 +/- 0.022 versus 0.022 +/- 0.016, P = 0.0008 arbitrary units of immunohistochemistry) as well as in their buccal mucosa cells (0.058 +/- 0.028 versus 0.028 +/- 0.012, P = 0.001). Also, there was a correlation between the levels of PAH-DNA adducts in mouth floor cells and those in buccal mucosa cells (r = 0.4, P = 0.01). Furthermore, PAH-DNA adduct levels in both mouth floor and buccal mucosa cells were significantly related to current smoking indices (amount of tar and number of cigarettes consumed per day). Expectedly, the levels of PAH-DNA adducts neither in mouth floor cells nor in buccal mucosa cells, both being short-lived cells, were related to smoking history index (pack years). The levels of PAH-DNA adducts, however, in mouth floor cells as the cancer prone cells were lower than those in buccal mucosa cells (0.037 +/- 0.023 versus 0.044 +/- 0.026, P = 0.04). We conclude that immunohistochemistry of PAH-DNA adducts in oral cells can be used for exposure assessment of tobacco-related carcinogens, however, it cannot be used for oral cancer risk estimation.     

Influences of DNA isolation and RNA contamination on carcinogen-DNA adduct analysis by 32P-postlabeling

³²P-Postlabeling is a widely applied assay for the analysis of carcinogen-DNA adducts. Optimization of most steps in this assay has been given attention, but influences of DNA isolation and DNA purity on adduct quantitation have not been investigated systematically. In this study, DNA was isolated from human lymphocytes exposed to benzo[a]pyrene (B[a]P, 10 μM) for 18 hr and from liver of rats i.p.-treated with B[a]P (10 mg/kg body weight) using two different DNA isolation methods: a phenol-extraction and a salting-out procedure. Subsequently, DNA was analysed by nuclease P1 (NP1) or butanol-enriched ³²P-postlabeling. Influences of RNA contamination were studied by labeling RNA isolated from in vitro exposed lymphocytes. In the in vitro experiment, DNA adduct levels were significantly higher using the salting-out procedure (63.2 ± 13.7 adducts per 10⁸ nucleotides, n = 9) as compared with the phenol-extraction (14.3 ± 0.8). RNA was ∼4 times less efficiently labeled as compared to DNA. Nonetheless, RNA contamination of DNA samples may result in an overestimation of DNA adduct levels when butanol enrichment is used, because RNA adduct levels seemed to be substantially higher than DNA adduct levels in the same cells. DNA adduct analysis by nuclease P1 enrichment is probably less affected, since RNA adducts appeared to be NP1 sensitive. In vivo, three different adducts were found by NP1 enriched ³²P-postlabeling in the liver of B[a]P-exposed rats. Again, DNA adduct levels were significantly higher using salting out as compared to phenol extraction for the adduct which comigrated with the BPDE-DNA adduct standard (adduct 1) and an unknown adduct (adduct 2). However, the results were the opposite for another B[a]P-derived DNA adduct (adduct 3). Our results suggest that differences in DNA isolation procedures as well as RNA contamination influence quantitative DNA adduct analysis by ³²P-postlabeling. Environ. Mol. Mutagen. 32: 344–350, 1998 © 1998 Wiley-Liss, Inc.     

Identification of Potent and Selective Glucosylceramide Synthase Inhibitors from a Library of N-Alkylated Iminosugars

l-ido-configured iminosugar. In particular, the selectivity of 27 for GCS over GBA1 is striking.     

The localisation of treponemes and characterisation of the inflammatory infiltrate in skin biopsies from patients with primary or secondary syphilis, or early infectious yaws.

OBJECTIVE--To study the localisation of treponemes and to analyse the inflammatory infiltrate in biopsy specimens from patients with primary or secondary syphilis, or early infectious yaws. MATERIALS AND METHODS--Skin biopsies originating from human lesions of primary (29x) or secondary (15x) syphilis (Rotterdam), or early yaws (18x) (West Sumatra) were studied. Different histochemical and immunohistochemical detection methods were used in this study. RESULTS AND CONCLUSION--The histochemical silver staining method according to Steiner revealed the presence of T. pallidum in all cases of primary syphilis studied. In 10 out of 14 cases of secondary syphilis, treponemes were demonstrated. With an immunofluorescence staining technique (IF) using anti-T. pallidum antiserum raised in rabbits (a-Tp), T. pallidum was demonstrated in 28 out of 29 cases of primary syphilis, and in 14 out of 14 studied cases of secondary syphilis. The silver staining method and IF showed identical localisations of T. pallidum (mainly in the dermal-epidermal junction zone or throughout the dermis). Using a-Tp antiserum in the indirect immunofluorescence technique, T. pertenue could be demonstrated in the dermis more often than with Steiner silver staining. However, epidermotropism of T. pertenue in yaws specimens was remarkable, compared with more mesodermotropism of T. pallidum; numbers of T. pertenue in the dermis were limited in all specimens. The dermal inflammatory infiltrate in primary and secondary syphilis was composed mainly of lymphocytes and plasma cells. In most cases more T (CD3 positive) cells than B (CD22 positive) cells were present. Regarding T cell subpopulations, in primary syphilis, T helper/inducer (CD4 positive) cells predominated in 86% of cases. In secondary syphilitic lesions, numbers of T helper/inducer cells were less frequent than or equal to T-suppressor/cytotoxic (CD8 positive) cells in 60% of cases. Remarkably, in yaws specimens the inflammatory infiltrate consisted mainly of IgG, but also IgA and IgM producing plasma cells. T or B lymphocytes were scarce, which is in sharp contrast with findings in syphilitic lesions.