Biomedical subjects

G M O'Brien

Publications and source records attributed to G M O'Brien.

31 records · Page 2Linked to original sources

PubMed1994

Paranoid psychosis due to neurosarcoidosis.

We present two patients with known sarcoidosis who developed neurosarcoidosis manifested by paranoid psychosis and clinical diabetes insipidus with hypernatremia. Both had gadolinium enhanced magnetic resonance imaging which demonstrated leptomeningeal and hypothalamic enhancement. Both had elevated protein and a lymphocytosis in their cerebrospinal fluid, which improved after corticosteroid therapy. The patients improved clinically with this therapy as well. We suggest that new onset psychosis in a sarcoid patient, particularly with symptoms of hypothalamic/pituitary involvement, should be evaluated for neurosarcoidosis with an MRI and CSF examination. If the results are consistent with neurosarcoidosis, the patient should be treated promptly with corticosteroids.

Adult↗

PubMed1993

Seasonal reproduction in flying foxes, reviewed in the context of other tropical mammals.

Megachiroptera inhabit the Old World tropics and most are seasonal breeders having defined times of testis growth, mating and parturition. In Pteropus scapulatus, the little red flying fox, the robust rhythm of testis cycles is resistant to modification by photoperiod. P. poliocephalus, the greyheaded flying fox, can be manipulated by photoperiod but responds slowly and incompletely. Most mammals live in the tropics, many in seasonally harsh climates, and many breed seasonally. However, few long-lived tropical mammals have been investigated for photoperiodic entrainment of annual reproductive cycles, and only animals from the edge of the tropics have responded. Thus, in long-lived tropical mammals, factors that regulate seasonal breeding have not yet been identified. Endogenous oscillators may generate circannual rhythms centrally. Downstream pathways (reproduction, metabolism, antlers, etc.) may derive their rhythm directly from the oscillator or may be modified by environmental cues. Plasticity of the circannual oscillator resolves confusion from previous contrasts between circannual rhythms and environmentally cued patterns. Plasticity may continue throughout life (species responsive to zeitgebers), but the oscillator may be 'set' in utero in some tropical species. Feedback effects from temperature, nutrition, hormones, etc. can be readily tested in this model of an oscillator generating an endogenous circannual rhythm.

Animals↗

PubMed1993

Effect of photoperiod on the annual cycle of testis growth in a tropical mammal, the little red flying fox, Pteropus scapulatus.

Little red flying foxes (Pteropus scapulatus) are seasonal breeders: they mate in late spring/early summer, and young are born the following autumn. In captivity, males housed outdoors in a normal breeding colony in natural daylight showed a single cycle of testis growth and regression each year. During reproductive quiescence, testicular volume was approximately 2 cm3; recrudescence began soon after the winter solstice; testicular volume was maximum at approximately 6.5 cm3 at the spring equinox; and regression was complete by the end of summer. To test whether photoperiod entrains or synchronizes the cycle, groups of males were housed indoors, without females, at constant temperature, and artificial lighting was timed to either mimic naturally changing daylength or provide alternating 3-month periods of short (11 h light:13 h dark) or long (16 h light:8 h dark) days (two groups, three months out of phase with each other). During 18 months, the applied photoperiod protocol had no effect on the frequency of testicular cycles (which remained at one per year), the time course of recrudescence and regression (as described above for normal outdoor control males), or the completeness of growth and regression stages. These results suggest that male P. scapulatus are not reproductively photoresponsive.

Animals↗

PubMed1992

Effects of different rates of drying cassava root on its toxicity to broiler chicks.

1. The effects of drying cassava root at different rates on its composition and toxicity to broiler chicks were examined. Unpeeled roots from a high-cyanide cultivar of cassava were chipped and dried at 25 degrees C to a moisture content of below 100 g/kg over 24 h for fast-dried meal (FD) or 72 h for slow-dried meal (SD). The meals were incorporated at 250 and 500 g/kg into semi-synthetic diets which were fed to day-old broiler chicks as mash or pellets in separate experiments. 2. The two drying rates produced meals with similar concentrations of polyphenols, but different concentrations of cyanogens, the latter being 38 and 482 mg total cyanide/kg for SD and FD, respectively. The linamarin, acetonecyanohydrin or total cyanide content measurements of pelleted diets were highly correlated. 3. Growth rates of chicks fed on SD-based diets were significantly higher than those of chicks fed on FD-based diets. Compared with a control diet, weight gain of chicks fed on the 500 g FD/kg diet (containing 258 mg total cyanide/kg) was 77% lower, although performance also appeared to be reduced at 142 mg total cyanide/kg. 4. The ratio of water:food intake of chicks was higher in FD than in SD groups, and this was reflected in the high water content of excreta. There was increased bile excretion, the chloretic effect increasing with the cyanogen content of diet. Pancreas weights were lower in FD than in SD groups in experiment 1 (mash diets), but not in experiment 2 (pelleted diets), while there was a significant interaction between drying method and cassava inclusion rate on liver weight in experiment 2, but not in experiment 1. There were no effects on the mortality rate. 5. Pelleting of diets generated high temperatures, but did not significantly alter the cyanogen concentration or the growth of the chicks. 6. Thus, slower rates of drying cassava roots produce meals with lower cyanogen concentration that are, consequently, less toxic to broiler chicks. Cassava root meal of less than 40 mg total cyanide/kg can be fed to broiler chicks at 500 g/kg without any adverse effects.

Animal Feed↗

PubMed1987

An osmium-191/iridium-191m radionuclide generator using an oxalato osmate parent complex.

A new osmium-191/iridium-191m (191Os/191mIr) radionuclide generator has been developed that offers high 191mIr yield (greater than 20%/ml) and low 191Os breakthrough (less than 5 X 10(-4)%/ml) when eluted with a solution of 0.001 M oxalic acid and 0.9% (normal) saline. This is the first 191Os/191mIr generator that combines the advantages of high 191mIr yield, extremely low 191Os breakthrough, and an eluate that does not require buffering prior to injection. These improvements in performance were accomplished through use of the chelate transdioxobisoxalatoosmate(VI) as the parent complex on the generator. The clinical result of the combination of higher yield and lower breakthrough is a 100-fold decrease in the estimated patient radiation dose compared with the same study performed with technetium-99m (99mTc), and the injectable eluate makes the generator easier to use. Acute and subacute toxicity studies performed on this generator eluate have shown no adverse effects attributable to the eluate.

Iridium↗

PubMed1986

The development of an 191Os----191mIr generator using an osmium chelate parent complex--I. Trans-dioxobismalonatoosmate(VI).

A 191Os----191mIr generator has been developed that has higher 191mIr yield and lower 191Os breakthrough than previous designs. These improvements have been realized through the use of the osmium chelate complex trans-dioxobismalonatoosmate(VI) as the parent species on the generator. The new generator provides an initial 191mIr yield of 40%/mL and 191Os breakthrough of 2-3 X 10(-3)% when eluted with a solution of 0.05 M malonic acid/0.10 M sodium chloride at pH 4. Other advantages of the new design include faster clearance of the 191Os breakthrough products and simpler assembly.

Angiography↗

PubMed1986

Comparison of ultrashort-lived iridium-191m with technetium-99m for first pass radionuclide angiocardiographic evaluation of right and left ventricular function in adults.

Ultrashort-lived iridium-191m (Ir-191m, physical half-life = 5.0 seconds) has been used in angiocardiography, primarily in pediatric patients. A theoretical obstacle to more widespread use of Ir-191m is the belief that its physical half-life is too short to permit evaluation of left ventricular function in adult patients. To evaluate its usefulness in adults, first pass ejection fractions of the left and right ventricles determined with use of Ir-191m and technetium-99m (Tc-99m) were compared in 33 adult patients. An osmium-191m----iridium-191m (Os-191----Ir-191m) generator was employed to deliver doses of 150 to 250 mCi (5.5 to 9.2 GBq) of Ir-191m for intravenous injection. The whole body radiation absorbed dose with Ir-191m was 15 to 25 mrad. High quality angiocardiograms were obtained with both Tc-99m and Ir-191m. Total counts per image for the right ventricle were 51,000 +/- 8,000 (mean +/- SD) for Ir-191m and 30,000 +/- 8,000 for Tc-99m. The left ventricular counts were comparable for both radiotracers (25,000 +/- 7,000 for Ir-191m and 25,000 +/- 8,000 for Tc-99m). Right ventricular ejection fractions were similar: 44 +/- 8% for Ir-191m and 47 +/- 9% for Tc-99m. The correlation coefficient was 0.93 with a standard deviation of the regression of 3.1% ejection fraction units. The left ventricular ejection fractions were also similar: 45 +/- 14% for Ir-191m and 46 +/- 13% for Tc-99m. The left ventricular ejection fraction correlation coefficient was 0.96 with a standard deviation of the regression of 3.7%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1978

The sarcoplasmic reticulum and T-system of rat extensor digitorum longus muscles exposed to hypertonic solutions.

Excised rat extensor digitorum longus muscles were soaked in a Krebs solution made hypertonic with extra NaCl and fixed using a combination of acrolein and glutaraldehyde dissolved in the same hypertonic Krebs. Electron microscopic examination showed that the sarcoplasmic reticulum (S.R.) of these muscles occupied the same fraction of fibre volume as it did in control muscles soaked and fixed in normal Krebs solution, contradicting previous studies on frog muscle. It appears unlikely that the S.R. is the rapidly exchanging Na+-compartment of rat muscle which enlarges in hypertonic solutions, or that it is an extracellular compartment. The T-system of hypertonic muscles was swollen, but its volume is insufficient to form the rapidly exchanging Na+-compartment.

Animals↗

PubMed1972