Multiple states of beta-sheet peptide protegrin in lipid bilayers

Protegrin-1 (PG-1), a beta-sheet antimicrobial peptide, was studied in aligned lipid bilayers by oriented circular dichroism (OCD). All of its spectra measured in a variety of lipid compositions were linear superpositions of two primary basis spectra, indicating that PG-1 existed in two different states in membranes. We designated these as state S and state I. The state assumed by PG-1 was strongly influenced by lipid composition, peptide concentration, and hydration condition. We have previously reported that the helical peptides, alamethicin and magainin, also exhibit two distinct OCD basis spectra-one corresponding to surface adsorption with the helix parallel to the bilayer and the other with perpendicular transbilayer insertion. States S and I of PG-1 may correspond to the surface state and the insertion state of alamethicin, since they show a similar dependence on lipid composition, peptide concentration, and hydration condition. Nonoriented CD spectra obtained from vesicle, micelle, and solution preparations are not linear superpositions of the basis spectra of the states S and I. This indicates that a molecular orientation change alone is insufficient to describe the S left and right arrow I transition. Rather, a more complicated process is taking place, perhaps involving a change in the hydrogen bonding pattern of the backbone. Although the structural basis of the OCD spectra remains to be determined, the discovery of two distinct states can provide information about dynamic changes of PG-1 in membranelike environments, properties undoubtedly related to its antimicrobial and cytotoxic effects.     

A novel adenylyl cyclase detected in rapidly developing mutants of Dictyostelium

Disruption of either the RDEA or REGA genes leads to rapid development in Dictyostelium. The RDEA gene product displays homology to certain H2-type phosphotransferases, while REGA encodes a cAMP phosphodiesterase with an associated response regulator. It has been proposed that RDEA activates REGA in a multistep phosphorelay. To test this proposal, we examined cAMP accumulation in rdeA and regA null mutants and found that these mutants show a pronounced accumulation of cAMP at the vegetative stage that is not observed in wild-type cells. This accumulation was due to a novel adenylyl cyclase and not to the known Dictyostelium adenylyl cyclases, aggregation stage adenylyl cyclase (ACA) or germination stage adenylyl cyclase (ACG), since it occurred in an acaA/rdeA double mutant and, unlike ACG, was inhibited by high osmolarity. The novel adenylyl cyclase was not regulated by G-proteins and was relatively insensitive to stimulation by Mn2+ ions. Addition of the cAMP phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX) permitted detection of the novel adenylyl cyclase activity in lysates of an acaA/acgA double mutant. The fact that disruption of the RDEA gene as well as inhibition of the REGA-phosphodiesterase by IBMX permitted detection of the novel AC activity supports the hypothesis that RDEA activates REGA.     

Minocycline treatment and pseudotumor cerebri syndrome

We performed a quantitative investigation of arginine-vasopressin (AVP) immunopositive neurons in the suprachiasmatic nucleus (SCN), which is the endogenous clock of the brain of a patient with multiple system atrophy (MSA) who exhibited nocturnal polyuria associated with decreased urinary specific gravity and depression of nocturnal AVP secretion. Eleven age- and sex-matched subjects were used as controls. Although, the number of AVP-positive neurons was decreased in neither the supraoptic nucleus nor the paraventricular nucleus, the number of AVP-positive neurons in the SCN was decreased and gliosis was present in the SCN. The cytoplasmic area of AVP-immunopositive neurons in the SCN was smaller in the patient than in the control subjects. These findings raise the possibility that SCN is involved in MSA and the neurodegeneration in the SCN results in altered circadian rhythm of AVP secretion and nocturnal polyuria.     

Metabolism of an anionic fluorescent dye, 1-anilino-8-naphthalene sulfonate (ANS) by rat liver microsomes

OBJECTIVE: To examine the association between chronic illness and functional status change during a 3-year period in older people enrolled in an in-home comprehensive geriatric assessment (CGA) and preventive care program. DESIGN: Secondary analysis of data from a longitudinal cohort study. SETTING: Santa Monica, California. PARTICIPANTS: Two hundred two community-dwelling older persons (mean age at baseline was 81 years, 70% were women, and 72% reported good health) randomized to the intervention group in a trial of in-home comprehensive geriatric assessment and preventive care. MEASUREMENTS: We studied 13 common chronic illnesses/conditions determined clinically from an annual comprehensive evaluation by gerontologic nurse practitioners (GNPs) in consultation with study geriatricians. These target conditions included hypertension, osteoarthritis, coronary artery disease, obesity, undernutrition, urinary incontinence, sleep disorders, falls, gait/balance disorders, hearing and vision deficits, depression, and unsafe home environment. The dependent variable was functional change as measured by instrumental activities of daily living (IADL) and basic activities of daily living (BADL) assessed at baseline and annually for 3 years by independent research personnel. Potential confounding variables, including comorbid conditions and other subject characteristics, were controlled for in the analyses. RESULTS: Although functional status was similar at baseline, the presence of certain target conditions in this sample was associated significantly with functional decline in IADL and BADL during the 3-year period. Four conditions (gait/balance disorders, depression, unsafe home environment, and coronary artery disease) were associated with significant declines in IADL, and four conditions (gait/balance disorders, depression, hypertension, and urinary incontinence) were associated with significant declines in BADL. Conversely, subjects with obesity had no significant change in IADL or BADL throughout the study period and had less decline in IADL compared with nonobese subjects. CONCLUSIONS: Certain chronic conditions, particularly gait/balance disorders and depression, are associated with significant decline in functional status in older persons who receive CGA. These findings may help identify older persons at risk for greatest functional decline despite participation in CGA and may also suggest the need for more effective intervention strategies in these individuals.     

Color mixing in dental porcelain

One hundred and two apparently healthy Indian domestic ducks from the Poultry Research Station, Madras were screened for duck hepatitis B virus (DHBV) infection by; 1. screening for the duck hepatitis B virus surface antigen (DHBsAg) in their sera using hepatitis B virus (HBV) reagents, 2. screening for DHBsAg using specific duck hepatitis B virus (DHBV) reagents and 3. demonstration of DHBV DNA using DHBV DNA probe by dot blot hybridisation. While 5 ducks (4.9%) were consistently positive with HBV reagents, use of DHBV reagents showed a total of 4 ducks (including 3 of the above 5) to be positive for DHBsAg. DNA hybridisation showed 6 ducks to be positive for DHBV DNA. On clinical examination, 5 out of these 6 ducks did not reveal abnormalities, the other one showed hepatomegaly and ascites. Post-mortem studies showed the presence of nodules on the surface of the liver in all 5 which were positive with HBV reagents including the one with hepatomegaly. On histopathological evaluation, they were found to be hepatocellular carcinoma with or without bile duct carcinoma. The present study is a pilot report on the occurrence of DHBV infection in Indian domestic ducks and the possibility of antigenic cross reactivity between human HBV and duck hepatitis B virus antigens.     

Treatment of recurrent malignant gliomas with chronic oral high-dose tamoxifen

The present clinical trial was undertaken to assess the clinical safety and possible efficacy of administering tamoxifen to patients with recurrent malignant glial tumors at dosages calculated to achieve levels sufficient to inhibit protein kinase C within the tumor cells. Chronic p.o. tamoxifen was administered in very high dosages to 32 patients (20 males and 12 females; age range, 26-75 years; mean, 49 years) with histologically verified malignant glioma [anaplastic astrocytoma (12 patients) or glioblastoma multiforme (20 patients)] who had demonstrated clinical and radiographical progression or recurrence following external beam radiation therapy (and additional chemotherapy in 11; immunotherapy in 2). The dosage of tamoxifen administered was 200 mg/day to males and 160 mg/day to females given in a twice daily schedule. Clinical and radiographical (defined as a greater than 50% decrease in volume of the enhancing lesion volume on magnetic resonance imaging and a decrease in metabolic activity on serial positron emission tomographic scans) response was noted in 8 patients (25%; 4/12 with anaplastic astrocytoma and 4/20 glioblastoma multiforme), with an additional 6 patients (19%) exhibiting stabilization of disease with minimal side effects. Median survival from the time of diagnosis for the entire cohort was 24 months (104 weeks), for the anaplastic astrocytoma group 42.5 months (185 weeks), and for the glioblastoma group 17.4 months (75.5 weeks). From the initiation of tamoxifen, median survival for the entire cohort was 10.1 months (44 weeks), for the anaplastic astrocytoma group 16 months (69 weeks), and for the glioblastoma group 7.2 months (31 weeks). The mean length of follow-up of all patients after initiating tamoxifen was 16 months (69 weeks), while the mean length of follow-up of alive patients is 22.6 months (98 weeks) (range up to 51 months). These data suggest that a subgroup of patients with malignant gliomas respond or stabilize with chronic high-dose tamoxifen therapy. This therapy may represent an alternative or adjuvant to existing chemotherapies for these tumors; further clinical trials are warranted.     

Alterations of lidocaine and pentylenetetrazol-induced convulsions by manipulation of brain monoamines

The thresholds for pentylenetetrazol and lidocaine-induced clonic convulsions were significantly influenced by manipulation of brain biogenic amines. Pretreatment with inhibitors of monoamine synthesis, alpha-methyl-p-tyrosine and p-chlorophenylalanine, caused significant decreases in brain monoamine contents and pentylenetetrazol seizure threshold, while the threshold for lidocaine-induced convulsions was significantly increased by either treatment. Moreover, the inhibitor of dopamine-beta-hydroxylase, disulfiram, caused significant decrease in brain noradrenaline (NA) and significant increase in brain dopamine (DA) contents. The threshold for pentylenetetrazol-induced convulsions was decreased by treatment with disulfiram, while that of lidocaine was increased by the same treatment. Furthermore, treatment with L-dihydroxyphenylalanine (L-DOPA) caused significant increase in brain DA contents, while 5-hydroxytryptophan (5-HTP) treatment caused significant increase in brain 5-hydroxytryptamine (5-HT) contents, but the thresholds for lidocaine and pentylenetetrazol-induced convulsions were not influenced by either treatment. These results may suggest that the brain monoaminergic systems, different from their ability to inhibit control of pentylenetetrazol seizures, act to potentiate lidocaine-induced convulsions.