Human hydroxyindole-O-methyltransferase in pineal gland, retina and Y79 retinoblastoma cells

Hydroxyindole-O-methyltransferase (HIOMT, EC 2.1.1.4) was studied in extracts of human pineal gland, retina and Y79 retinoblastoma cells. HIOMT enzyme activity and immunoreactive protein (approximately 42 kDa) were undetectable in the human retina; very low levels of HIOMT mRNA were detected using a highly sensitive RT-PCR/Southern blot method, as has been reported. Analysis of extracts of Y79 cells indicated that HIOMT enzyme activity, immunoreactivity (approximately 42 kDa) and mRNA (approximately 1.3 kb) were detectable at approximately 1/5-1/40 the levels found in the pineal gland. This unambiguously establishes that the HIOMT gene is expressed in Y79 cells. Kinetic analysis of Y79- and pineal-derived HIOMT indicates that the enzyme is generally similar in both tissues; one difference, however, is that substrate inhibition by N-acetylserotonin is greater with the Y79-derived enzyme. These studies show that Y79 cells represent a valid model to study the regulation of human HIOMT protein and mRNA; the differences detected may reflect the existence of tissue-specific regulatory mechanisms or differential patterns of expression of HIOMT isoforms.     

Foreperiod duration, range, and ordering effects on acoustic LRT in normal speakers

One quantitative measure of vocal motor control is phonation onset latency relative to presentation of an external stimulus in a reaction time task. However, variables within the design of reaction time experiments can affect laryngeal reaction time (LRT) values. The present study examines effects of foreperiod characteristics on LRT for normal speakers. Foreperiod is the interval between presentation of warning and response cues. LRT was affected by absolute foreperiod duration, by the average foreperiod duration of a block of trials, and by the ordering and range of foreperiods within a block of trials. Results are discussed with respect to foreperiod effects on the subjective expectancy and objective probability of occurrence of the response cue and on the timing of neurophysiologic processes. Control of subjective effects is critical to assessment of neurophysiologic constraints on LRT.     

Chordoma with cutaneous metastasis

Chordoma is a neoplasm arising from the primitive notochord. Even though many chordomas follow a progressive course with multiple recurrences and metastases and eventual death due to tumor, reports of skin metastases from chordoma are rare. This report describes a case of chordoma with metastasis to the scalp in a 67-year-old man with a primary lesion of the sacrococcygeal region.     

Experimental reproduction of bovine fetal Neospora infection and death with a bovine Neospora isolate

It is well established that alpha 2-adrenoceptor agonists have sedative and antinociceptive properties. In the current behavioral study we tried to find out if the alpha 2-adrenergic sedative and antinociceptive effects can be dissociated. We tested the hypothesis that alpha 2-adrenergic sedation is mediated by the locus coeruleus (LC) and antinociception by spinal alpha 2-adrenoceptors. Also, we addressed the possibility that intracerebral injection of an alpha 2-agonist might produce its antinociceptive effect by an action directly at the spinal cord. Medetomidine, an alpha 2-adrenergic agonist, or atipamezole, an alpha 2-adrenergic antagonist, were microinjected bilaterally into the LC through chronic cannulae in unanesthetized Han-Wistar rats. The effect on locomotor activity (/vigilance), tail-flick and hot-plate response, and on formalin-induced pain behavior was determined. Medetomidine microinjected into the LC (1-10 micrograms/cannula) produced dose-dependently hypolocomotion (/sedation), increase of response latencies in the hot-plate and the tail-flick tests, and a decrease in the formalin-induced pain behavior. Hypolocomotion (/sedation) was obtained at a lower medetomidine dose (1 microgram/cannula) than antinociception (3-10 micrograms/cannula). The lowest medetomidine dose used (1 microgram/cannula), which induced significant hypolocomotion (/sedation), produced either no antinociception (hot-plate and tail-flick tests) or even a slight hyperalgesia (formalin test). The hypolocomotion (/sedation) but not antinociception (tail-flick test) induced by systemic administration of medetomidine (100 micrograms/kg s.c.) could be reversed by atipamezole (10 micrograms/cannula) microinjected into the LC. Only a high systemic dose of atipamezole (1 mg/kg s.c.) reversed the antinociceptive effects of medetomidine.(ABSTRACT TRUNCATED AT 250 WORDS)     

The importance of measured intake in assessing exposure of breast-fed infants to organochlorines

OBJECTIVES: To estimate infants' intake of organochlorines (OCs) from their measured intake of breast milk; to compare these with the acceptable daily intakes (ADIs) set by the World Health Organization (WHO). DESIGN: Primiparous nursing mothers were recruited from either an industrial or rural area between January and November 1992. SETTING: Mothers volunteered in response to information displayed at their Infant Welfare Centre. All sampling was undertaken in the subject's home. SUBJECTS: The sole entry criterion was primiparity. Three breast milk samples were collected at one month intervals from each mother. OC levels were measured on a milk fat basis by gas chromatograph-mass spectrometer and individual milk intakes were used to determine the infant's daily OC intake. Of the 23 mothers who entered the study, 17 finished, resulting in 57 samples for intake determination. RESULTS: Some intakes of hexachlorobenzene (HCB), chlordane, dieldrin and heptachlor epoxide (HE) exceeded the ADI. High OC levels in breast milk did not necessarily result in a high intake for the infant. CONCLUSIONS: Assessment of the exposure of infants to OC contaminants in breast milk requires an accurate estimate of OC intake. Intakes estimated using inferred rather than measured values for milk fat and milk intake are not reliable indicators of actual intakes.     

Localization of a gene for M?bius syndrome to chromosome 3q by linkage analysis in a Dutch family

M?bius syndrome (MIM no. 157900) consists of a congenital paresis or paralysis of the VIIth cranial nerve, frequently accompanied by paralysis of other cranial nerves, orofacial and limb malformations, defects of the musculoskeletal system and mental retardation. Although most patients are sporadic cases, familial recurrence is not rare. Different pedigrees suggest different modes of inheritance. We performed linkage analysis in a large family with autosomal dominantly inherited M?bius syndrome, consisting essentially of asymmetric bilateral facial pareses. After exclusion of the candidate region for M?bius syndrome on 13q12.2-q13, we localized the gene to chromosome 3q21-22, indicating genetic heterogeneity of M?bius syndrome. This heterogeneity is further proven by the exclusion of both loci in a second family with M?bius syndrome.     

Optimization of parameters for the detection of cerebral aneurysms: CT angiography of a model

PURPOSE: To optimize parameters with computed tomographic angiography for the detection of cerebral aneurysms. MATERIALS AND METHODS: Model aneurysms were placed randomly at various branch points and scanned multiple times with spiral technique. The final analysis included 63 branch points and 22 aneurysms. Each spiral scan used a different parameter combination. Collimation ranged from 1.5 to 4.0 mm and pitch ranged from 1:1 to 1.5:1. Images were constructed with shaded surface display (SSD) and maximum intensity projection (MIP) algorithms and were interpreted by three readers for the presence or absence of aneurysm. RESULTS: The receiver operating characteristic (ROC) curve area for 1.5-mm collimation was greater than those of 3- or 4-mm collimation (P < .01 and P < .001, respectively). There was no statistically significant difference in the ROC curve areas between 3- and 4-mm collimation (P = .37). There was no statistically significant decrease in ROC curve area when increasing pitch from 1:1 to 1.5:1 for any value of collimation (P = .96). For all parameter combinations the ROC curve areas for SSD images was greater than that of MIP images (P < .0001). CONCLUSION: For cerebral aneurysm detection, narrow collimation is superior to wider collimation. Mild increases in pitch do not substantially degrade diagnostic accuracy. SSD offers improved diagnostic accuracy over MIP display in this model.     

17 beta-estradiol hydroxylation catalyzed by human cytochrome P450 1B1

The 4-hydroxy metabolite of 17 beta-estradiol (E2) has been implicated in the carcinogenicity of this hormone. Previous studies showed that aryl hydrocarbon-receptor agonists induced a cytochrome P450 that catalyzed the 4-hydroxylation of E2. This activity was associated with human P450 1B1. To determine the relationship of the human P450 1B1 gene product and E2 4-hydroxylation, the protein was expressed in Saccharomyces cerevisiae. Microsomes from the transformed yeast catalyzed the 4- and 2-hydroxylation of E2 with Km values of 0.71 and 0.78 microM and turnover numbers of 1.39 and 0.27 nmol product min-1.nmol P450-1, respectively. Treatment of MCF-7 human breast cancer cells with the aryl hydrocarbon-receptor ligand indolo[3,2-b]carbazole resulted in a concentration-dependent increase in P450 1B1 and P450 1A1 mRNA levels, and caused increased rates of 2-, 4-, 6 alpha-, and 15 alpha-hydroxylation of E2. At an E2 concentration of 10 nM, the increased rates of 2- and 4-hydroxylation were approximately equal, emphasizing the significance of the low Km P450 1B1-component of E2 metabolism. These studies demonstrate that human P450 1B1 is a catalytically efficient E2 4-hydroxylase that is likely to participate in endocrine regulation and the toxicity of estrogens.