The cluster model of ultraviolet disinfection explains tailing kinetics.

AIMS: To develop a new mathematical model derived from first principles to define the kinetics of ultraviolet disinfection and to explain the phenomenon known as tailing. The theory presented interprets tailing as the result of photoprotection due to cumulative Mie scattering effects in clustered populations of micro-organisms. METHODS AND RESULTS: Mie scattering effects at ultraviolet wavelengths are used to compute a shielding constant for each micro-organism based on the average projected diameter. An intrinsic rate constant, hypothesized to be a characteristic property of the microbial genome alone, is computed. The cluster model is fitted to tailing data from 30 ultraviolet inactivation studies and results are compared with the classic two stage multihit model. CONCLUSIONS: The cluster model demonstrates a statistically significant improvement in the mean adjusted R2 values of the tested data sets (P < 0·0001). Tailing in survival curves is the direct consequence of the Gaussian distribution of cluster sizes and the intrinsic rate constant is a real and critical parameter that defines ultraviolet susceptibility. SIGNIFICANCE AND IMPACT OF THE STUDY: The ultraviolet dose-response behaviour of micro-organisms can now be explained in terms of parameters that have physical meaning and provide deep insight into the disinfection process.

Communicating with parents of premature infants: who is the informant?

OBJECTIVES: To determine what sources of information are most helpful for neonatal intensive care unit (NICU) parents, who provides NICU parents with the information, and also what expectations parents have regarding obtaining information. STUDY DESIGN: A 19-item questionnaire was given to the parents of infants 32 weeks or younger prior to discharge from the NICU. RESULTS: Out of the 101 parents who consented, almost all of the parents (96%) felt that 'the medical team gave them the information they needed about their baby' and that the 'neonatologist did a good job of communicating' with them (91%). However, the nurse was chosen as 'the person who spent the most time explaining the baby's condition, 'the best source of information,' and the person who told them 'about important changes in their baby's condition' (P<0.01). CONCLUSION: Although the neonatologist's role in parent education is satisfactory, the parents identified the nurses as the primary source of information.

Demonstration of a hermetic airborne ozone disinfection system: studies on E. coli.

An enclosed flow-through system using airborne ozone for disinfection and which removes the ozone with a catalytic converter was tested with a strain of Escherichia coli. Petri dishes containing the microorganisms were inserted in a chamber and exposed for 10-480 min to ozone concentrations between 4 and 20 ppm. Death rates in excess of 99.99% were achieved. Survival data is fitted to a two-stage curve with a shoulder based on the multihit target model. Ozone was removed from the exhaust air to nondetectable levels using a metal oxide based catalyst. The possibility of using ozone as an airborne disinfectant for internal building surfaces and catalytically removing the ozone on exhaust is demonstrated to be feasible. A model for the decay of Bacillus cereus under ozone exposure is proposed as an example for predicting the sterilization of buildings contaminated with anthrax. The potential for disinfecting airstreams and removing ozone to create breathable air is also implied by the results of this experiment.

Engineering control of airborne disease transmission in animal laboratories.

We here present a review of the problem of controlling airborne disease transmission in animal research facilities, with emphasis on engineering design and air-treatment technologies. Dilution ventilation, pressurization control, source control, and air disinfection and removal systems are reviewed, and analytical studies on the effects of dilution ventilation, filtration, and ultraviolet germicidal irradiation are summarized. In addition, we discuss practical problems common to laboratory facilities and present a database of potential airborne pathogens and allergens that can be transmitted between humans and animals. We offer some conclusions regarding the design and selection of available technologies and components and provide cost estimates for various air-cleaning systems.

Estimation of bioavailability of selected magnesium organic salts by means of molecular modelling.

In the present work the selected organic magnesium salts were characterised by means of molecular mechanics procedures. The most probable geometrical structures were determined by the optimisation of geometry and conformational research. The following QSAR parameters were determined: the molecular surface areas, volumes and log P. Parameters describing the geometrical structure were compared with the log P values in order to estimate the bioavailability of magnesium in the studied compounds. The magnesium ions better penetrate through biological membranes in form of chelates, where the ionic bonds are "hidden" in the interior of the reversibly formed intramolecular complexes. A correlation between the geometrical structure and the intensity of migration of studied magnesium salts was proposed with the aid of the mentioned QSAR parameters: the higher volume of the molecular form, the lower the penetration velocity. The penetrating molecules exhibit however a certain degree of polarity, both the too low and too high polarity can influence their penetration possibility.

Biotransformation of phosphogypsum in media containing different forms of nitrogen.

Studies on the biotransformation of phosphogypsum (a waste product formed in the course of the production of phosphorous fertilizers) with the use of sulfate reducing bacteria (SRB) demonstrated that it is a good source of sulfates and biogenic elements for these bacteria, though the addition of organic carbon and nitrogen is necessary. The aim of this study was to investigate the form of nitrogen and C:N ratio in the medium on the growth of SRB community in cultures containing phosphogypsum. Batch community cultures of sulfate reducing bacteria were maintained in medium with phosphogypsum (5.0 g/l), different concentrations of sodium lactate (1.6 - 9.4 g/l) and different forms (NH4CI, CO(NH2)2, KNO3) and concentrations (0 - 250 mg/l) of nitrogen. The growth of SRB was studied in the C:N ratio of from 2:1 to 300:1. It was found that: 1 - the best source of nitrogen for SRB is urea, followed by ammonium, the worst were nitrates; 2 - the bacteria were also able to grow in medium without nitrogen but their activity was then by approximately 15% lower than in optimal growth conditions; 3 - in medium with KNO3 inhibition of sulfate reduction by approx. 50% was observed; 4 - the highest reduction of nitrates (removal of nitrate) in media with phosphogypsum and nitrates was at limiting concentrations of sodium lactate. This is probably caused by the selection under these conditions (low concentration of hydrogen sulfide) of denitrifying bacteria or sulfate reducing bacteria capable of using nitrates as an electron acceptor.

Diurnal changes in plasma prolactin during the last one third of pregnancy in the baboon.

Previous studies in our laboratory revealed that daily plasma prolactin (Prl) levels were higher in the evening than in the morning in the pregnant baboon suggesting a diurnal variation. The goal of this study was to examine in more detail the diurnal alterations in plasma Prl levels. A tethered pregnant baboon model was utilized for these studies. Hourly venous blood samples were taken from 0700 to 2400 hr (n=10) or until 0700 hr the following day (n=5). The studies were performed at various days of pregnancy from day 135 until delivery. Plasma samples were analyzed for Prl by radioimmunoassay. A surge in plasma Prl was detected, starting around 1500 to 1600 hr and lasting for 3 to 5 hr. The surge occurred before the lights went off in the colony (1800 hr). Baseline Prl levels were higher in animals < 15 days before delivery compared to those > 15 days before delivery (P < 0.05). In contrast, no differences were found in the average peak Prl values between these two groups of animals. In summary, in the pregnant baboon during the last one-third of pregnancy plasma Prl surges, beginning around 1500 to 1600 hr and lasting for 3 to 5 hr. Less than 15 days before delivery the mean baseline Prl levels are higher compared to animals greater than 15 days before delivery.

[Platelets oxygen metabolism in women and men in different age groups]. / Metabolizm tlenowy krwinek plytkowych u kobiet i mezczyzn w róznym wieku.

The aim of the study as to assess the influence of the physiological aging process on the platelet cell metabolism in middle-aged people. A group of 17 healthy women (aged 47-59 years), and a group of healthy men (aged 45-60 years) were examined. The control group was composed of healthy women aged 19-25 years, and healthy men aged 19-27 years. The activity of hyperoxide dismutase, catalase, glutathione peroxidase and the concentration of malonyldialdehyde were determined in platelets. In comparison to the control group, a significant decrease in the activity of hyperoxide dismutase and glutathione peroxidase as well as an enhanced concentration of malonyldialdehyde were observed in the group studied. Moreover, a diminished catalase activity was noted in platelets of men, while in women there were no significant changes. The study indicated that disorders in the function of thrombocytes, an excessive generation of oxygen free radicals, and impaired mechanisms of cellular antioxidative defence accelerate atherosclerosis and aging process. Therefore, it is necessary to cover middle-aged people, particularly those occupationally exposed to factors affecting defence mechanisms, with adequate preventive programmes.

Effect of pregnancy on the metabolic clearance rate and the volume of distribution of oxytocin in the baboon.

Pharmacokinetic parameters of oxytocin (OT) metabolism were determined during the last third of pregnancy and again 4-8 wk after delivery in the baboon. Animals were placed on a tether system with venous and arterial access and a continuous monitoring of uterine contractions during gestation. Two methods of determining OT pharmacokinetics were utilized (bolus injection vs. continuous infusion). The metabolic clearance rate of OT as determined during the bolus trials (n = 7) was 22.2 +/- 1.5 ml.min-1.kg-1 in pregnancy and 16.3 +/- 1.4 ml.min-1.kg-1 postpartum (P < 0.05), respectively, and 23.7 +/- 2.8 vs. 16.9 +/- 3.7 ml.min-1.kg-1 (P < 0.05), respectively, as determined during the 1-h infusion trials (n = 4). The initial dilution volume and the volume of distribution at steady state of OT after administration did not differ between pregnant and postpartum animals (P > 0.05). The mean residence time (MRT) of OT was shorter during pregnancy, 7.7 +/- 0.8 vs. 10.8 +/- 1.2 min postpartum (P < 0.05). In summary, OT metabolism during pregnancy in the baboon is characterized by 1) increased clearance rate (1.4-fold), 2) accelerated turnover due to the shorter MRT, and 3) unaltered distribution.

Hormone replacement therapy usage: a 10 year experience of a solo practitioner.

The objective of this study was to identify factors affecting hormone replacement therapy (HRT) usage among patients of a single physician. All active patients (n = 330) given a HRT prescription over the past 10 years (1985-1995) by the physician were sent a questionnaire on health knowledge, lifestyle patterns, general medical and reproductive histories, responses to HRT usage and decision-making about HRT use. A total of 214 useful questionnaires were returned giving a response rate of 65%. For this cohort, the length of HRT use for those still taking HRT was 60 months; and for those no longer taking HRT, it was 32 months; and 85% of those ever given an HRT prescription were still using HRT at the time of survey. The educational backgrounds, exercise patterns, health knowledge, medical and reproductive histories of this group were representative of those found among suburban postmenopausal women in central Pennsylvania. Among this cohort, the most important reason for them taking HRT was the physicians' recommendation.

Multiple sclerosis: the frequency of allelic forms of tumor necrosis factor and lymphotoxin-alpha.

The cytokines LTa and TNF have been implicated as major mediators of tissue injury in multiple sclerosis (MS). In this study we have assessed the frequency of specific polymorphisms for these genes in MS (n = 53) and controls (n = 81) using a highly sensitive, two stage nested polymerase chain reaction (PCR), with the second stage using mutation-specific primers. Genomic DNA was extracted from blood cells and the results confirmed by direct dideoxy chain termination sequencing. The frequency of the -308 G to A mutation in the TNF promoter region in normal controls was 15% and in MS was 24%. For LTa gene the exon 3 polymorphism allele A was detected in 36% of controls and 34% of the MS patients. In MS, the combined genotype TNF G + A and LTa C + C was present 6 times more frequently (12%) than in controls (2%), and patients with this genotype showed the highest EDSS scores. We found the TNF and LTa polymorphisms to occur independently from the HLA class II DR2 allele distribution in MS. Whilst the G - A polymorphism in TNF gene promoter has been studied previously in MS, with conflicting results, this is the first study that has addressed the exon 3 polymorphism in LTa in MS. The results indicate that this polymorphism is not linked with the higher genetic predisposition for MS, but that combined TNF G + A and LTa C + C genotype might contribute to development of the disease.

Morphine inhibits nocturnal oxytocin secretion and uterine contractions in the pregnant baboon.

Morphine is a potent inhibitor of nocturnal uterine contractions (UCs) in the pregnant baboon, and these contractions are known to be induced by oxytocin (OT). The purpose of this study was to determine the mode of action of morphine in inhibiting nocturnal UCs by examining the effect of morphine on OT secretion, OT clearance, and uterine responsiveness to OT. A tethered pregnant baboon model during the last third of gestation was used for these experiments. In study 1, the effects of morphine or control saline on OT release and on spontaneous nocturnal UCs were examined. Study 2 determined the effects of morphine or control saline on the pharmacokinetics of OT after a bolus injection of OT. To exclude/include direct opiate effects on UCs, study 3 examined the responsiveness of the uterus to exogenous OT after morphine or control saline administration. Plasma OT levels were analyzed by RIA after extraction. UCs were assessed by frequency, amplitude, duration, and area under the curve. During nocturnal UCs, morphine, but not saline, administration resulted in the precipitous suppression of integrated OT levels (p < 0.05) to 42% of pretreatment values at 0-15 min postinjection and 17% at 30-45 min. Simultaneously, UCs were significantly suppressed (p < 0.05) by 75% at the 30- to 45-min interval. By 1 h, 5 of 7 animals showed no UCs. In study 2, morphine consistently increased the metabolic clearance rate (MCR) of OT in all trials (p < 0.05), although the magnitude of this effect was small (median 9%). Finally, study 3 demonstrated that myometrial responsiveness to the challenge of exogenous OT was not depressed by opiate administration (p > 0.05). To summarize, the decrease in nocturnal UCs after morphine is primarily due to an inhibition of OT release, and perhaps, but to a much lesser extent, an increase in OT MCR. There was no evidence of a direct tocolytic effect of morphine on the uterus. In conclusion, opioids such as morphine are potent inhibitors of nocturnal UCs and act by suppressing OT release in the pregnant baboon.

Response of the primate secretory endometrium to subchronic hypercortisolemia.

OBJECTIVE: To assess the impact of subchronic and moderate hypercortisolism on the secretory endometrium of the cynomolgus monkey. METHODS: Osmotic pumps containing hydrocortisone phosphate (HP) were implanted subcutaneously in each monkey on the first day of the menstrual cycle; each monkey also received pumps containing saline in another cycle. Blood was obtained three times per week and urine was collected daily for hormone analyses. Endometriectomy was performed 13 +/- 1 days after the serum estradiol (E2) peak in each study cycle. RESULTS: Infusion of HP elevated serum cortisol levels by an average of 70%. Mean serum progesterone (P) levels were decreased by 50% during the secretory phase of HP-treatment cycles by comparison with self-control cycles (P < .01); as a result, the mean endometrial glycogen concentration was reduced by 30% (P < .05) and the activity of 17 beta-hydroxysteroid dehydrogenase was decreased by 70% (P < .05). Serum E2 levels were not consistently elevated by HP treatment, but cytosolic estrogen receptor levels of the endometrium were decreased by 50% (P < .01), indicating increased estrogenic stimulation. Histologic development of the secretory endometrium was retarded, but the length of the secretory phase was not affected by the treatment. CONCLUSION: A moderate elevation of serum cortisol levels over one menstrual cycle consistently produced a reduction in serum P and a hypoprogestogenic-hyperestrogenic response of the secretory endometrium in the cynomolgus monkey.

Strategies for ovulation induction and oocyte retrieval in the lowland gorilla.

PURPOSE: Ovulation induction and oocyte retrieval were performed in a lowland gorilla in an attempt to propagate and potentially cryopreserve embryos from an infertile animal and to advance techniques to help preserve this endangered species. RESULTS: Following 34 days of leuprolide acetate suppression, human menopausal gonadotropins were administered for 14-days in a 32-year-old wild-born lowland gorilla. Ten oocytes were retrieved by transrectal ultrasound-guided aspiration. Other approaches to oocyte recovery were not feasible in this case. A serum estradiol concentration of 4700 pg/ml at the time of human chorionic gonadotropin administration did not induce ovarian hyperstimulation. Mature oocytes were recovered from follicles measuring 14 to 24 mm in diameter, with a corresponding average serum estradiol concentration of approximately 300 pg/ml for each mature follicle. Cryopreservation of a gorilla embryo was effected from cryopreserved gorilla spermatozoa. CONCLUSIONS: Parameters for monitoring ovulation induction in the gorilla appear to be similar to those for humans. The results indicate that the use of a gonadotropin releasing hormone agonist and higher doses of gonadotropins than previously used in gorillas appear to improve oocyte recovery.

The effect of respiratory activity on brain blood flow during exposure to +Gz acceleration.

The effect of respiratory activity on cardiovascular system during the exposure to +Gz acceleration was studied. For simultaneous, beat to beat evaluation of central and global cerebral blood flow, the system based on modified impedance cardiography method was used. The mechanism of modulation of the central and peripheral (cerebral) venous pressures and blood flow by intrathoracic pressure changes, has been shown. The data obtained from these studies suggest that reconsideration of the respiration technique during Anti-GSM seems indispensable.

Disappearance and unexpected reappearance of progesterone in the circulation of the monkey: novel hormone kinetics.

1. Intravenous injection of [3H]progesterone in non-pregnant monkeys resulted in total disappearance of the labelled hormone from the circulation within 3 h. However, 0.5-1.75 h after disappearance the hormone reappeared, reaching 20% (median, 5%) of the initial maximal concentration. 2. Reappearance of labelled hormone was accompanied by similar fluctuations in the levels of labelled metabolites, [3H]20 alpha-dihydroprogesterone and [3H]17 alpha-hydroxyprogesterone, which reached 61% (median, 14%) and 120% (median, 13%), respectively, of the initial maximal concentrations. 3. Chromatography was used to separate labelled progesterone and its metabolites. Efficiency of the procedure was determined separately in each sample and for each steroid. All data were corrected for percentage recovery. 4. Analytical equations were devised, based on the theory of compartmental systems with continuously distributed time lags, to describe the unexpected kinetics of progesterone levels. The coefficients of determination ranged from 86 to 99% (median, 96%) which indicates that the equations enabled reliable prediction of hormone levels in blood within the time range studied. 5. The unexpected reappearance of labelled progesterone cannot be explained by hormone secretion but only by a delayed release from tissue stores, since progesterone does not undergo enterohepatic recirculation. Thus, a previously undescribed mechanism affecting circulating progesterone levels, and perhaps those of other hormones, exists.

[Computer analysis of nystagmus]. / Komputerowa analiza sygnalu ENG.

An algorithm for the computer analysis of nystagmus is described in this paper. This algorhythms was based on digital differentiator, which monitors the eye position. The computed eye velocity is next used as an input to the fast phase detector. Several procedures, including minimum velocity test, slope sense test, SPV and FPV relationship test are invoked to extract the fast phases from the recorded signal. Based on three-years experience (approx. 3000 examinations) using the ENG-PC System in clinical practice we can conclude, that application of the nystagmus detector was useful in most cases. In our opinion, despite from system imperfection which is observed during the analysis of recording disturbed by artifacts, this system has unquestionable advantage over the traditional technique.

Microtubule-Based Movements During Ooplasmic Segregation in the Medaka Fish Egg (Oryzias latipes).

We used time-lapse video microscopy to monitor the effects of cytochalasin D (CCD) and demecolcine on cytoplasmic streaming toward the animal pole of the medaka egg, the formation of the blastodisc at the animal pole, the movement of oil droplets in the cytoplasm toward the vegetal pole, and the saltatory movement of small cytoplasmic parcels toward the animal pole and vegetal pole. Cytochalasin D inhibited both cytoplasmic streaming toward the animal pole and the formation of the blastodisc, suggesting a role for microfilaments in these processes. However, CCD had no apparent effect on saltatory movement or on the movement of oil droplets toward the vegetal pole. Thus, the segregation of oil droplets toward the vegetal pole is not the result of the bulk movement of ooplasm toward the animal pole. In eggs treated with demecolcine, oil droplets did not move toward the vegetal pole but instead floated to the uppermost portion of the egg, and saltatory movement was absent, suggesting that microtubules are required for these movements. The effects of demecolcine on oil droplet movement and saltatory movement could be reversed by irradiating the eggs with UV light (360 nm). Using indirect immunofluorescence, we showed that irradiation of demecolcine-treated eggs with UV light regenerated microtubules within the irradiated region. The specificity of the mechanism responsible for the vegetal poleward movement of oil droplets was assessed by microinjecting droplets of five other fluids--mineral oil, silicone oil, vegetable oil, and two fluorinated aliphatic compounds--into the ooplasm. None of these fluids segregated with the endogenous oil droplets. These results suggest that a specific mechanism, probably involving microtubules, is responsible for the segregation of oil droplets to the vegetal pole.

Pharmacokinetics and pharmacodynamics of anordrin (2 alpha, 17 alpha-diethynyl-A-nor-5 alpha-androstane-2 beta, 17 beta-diol diproprionate).

In order to determine the pharmacokinetics of anordrin a dose of 0.2 mg/kg of [3-14 C]anordrin was administered i.v. to 5 cynomolgus monkeys; the same monkeys received the same dose i.m. at a later date. An additional 3 monkeys received 1.0 mg/kg of [3-14C]anordrin i.m. After administration of the compound, the dipropionate esters of anordrin were rapidly hydrolyzed to the dihydroxy parent compound, anordiol. After i.v. administration, anordrin had a mean residence time (MRT) of 5.0 +/- 1.3 (SE) min. [14C]Anordiol formed from [14C]anordrin had an MRT of 139 +/- 27 (SE) min. The metabolic clearance rates (MCR) of anordrin and anordiol were 55 and 34 mL/min.kg, respectively. The apparent volume of distribution at steady state (Vss) for anordrin was 276 mL/kg, 7.5% of body weight of the animals; anordrol had a much larger Vss of 4460 mL/kg. The MRT of anordiol after i.m. administration of 1.0 mg/kg of [14C]anordrin was 26.3 days. An average of 44% of the dose appeared in urine regardless of the route of administration or dose. The MRT values of total radioactivity were the same when calculated from serum or urine after an i.v. dose, but after i.m. administration, values from urine were approximately 60% of that calculated from serum, indicating that products appearing in urine had a shorter MRT than products appearing primarily in feces. A separate group of monkeys was given anordrin i.m. in doses ranging from 0.1 to 0.4 mg/kg on the first day of menses. The regression of length of menstrual cycle on dose was significant (P = 0.004).(ABSTRACT TRUNCATED AT 250 WORDS)