An outbreak of meticillin-resistant Staphylococcus aureus colonization in a neonatal intensive care unit: use of a case-control study to investigate and control it and lessons learnt.

AIM: To describe the investigation and management of a meticillin-resistant Staphylococcus aureus (MRSA) outbreak on a neonatal intensive care unit (NICU) and the lessons learnt. METHODS: This was an outbreak report and case-control study conducted in a 40-cot NICU in a tertiary referral hospital and included all infants colonized/infected with gentamicin-resistant MRSA. INTERVENTION: Standard infection-control measures including segregation of infants, barrier precautions, enhanced cleaning, assessment of staff practice including hand hygiene, and increased MRSA screening of infants were implemented. Continued MRSA acquisitions led to screening of all NICU staff. A case-control study was performed to assess staff contact with colonized babies and inform the management of the outbreak. FINDINGS: Eight infants were colonized with MRSA (spa type t2068), one of whom subsequently developed an MRSA bacteraemia. MRSA colonization was significantly associated with lower gestational age; lower birthweight and with being a twin. Three nurses were MRSA colonized but only one nurse (45) was colonized with MRSA spa type t2068. Multivariable logistic regression analysis identified being cared for by nurse 45 as an independent risk factor for MRSA colonization. CONCLUSIONS: Lack of accurate recording of which nurses looked after which infants (and when) made identification of the risk posed by being cared for by particular nurses difficult. If this had been clearer, it may have enabled earlier identification of the colonized nurse, avoiding subsequent cases. This study highlights the benefit of using a case-control study, which showed that most nurses had no association with colonized infants.

Scaling behavior near jamming in random sequential adsorption.

For the random sequential adsorption model, we introduce the "availability" as a variable corresponding to the number of available locations in which an adsorbate can be accommodated. We investigate the relation of the availability to the coverage of the adsorbent surface over time. Power law scaling between the two is obtained both through numerical simulations and analytical techniques for both one- and two-dimensional random sequential adsorption, as well as in the case of competitive random sequential adsorption in one dimension.

Endometriosis affects sperm-endosalpingeal interactions.

BACKGROUND: The interaction between spermatozoa and the epithelium of the isthmic region of the uterine tube is thought to be an important part of the mechanisms of sperm transport to the site of fertilization and in preparing them for fertilization. However, it is unclear whether a dysfunction of this mechanism may contribute to subfertility in some individuals. METHODS: The sperm-binding characteristics of the epithelium from the uterine tubes of three groups of women were examined: (i) eight with pelvic endometriosis (not involving the uterine tubes); (ii) five women who had been receiving zoladex injections to control their symptoms; and (iii) as controls 10 women undergoing an elective procedure for benign gynaecological problems but with no other pathology of the reproductive tract. RESULTS: Significantly more spermatozoa bound per unit area to the ampullary epithelium of the uterine tubes taken from women with a previous diagnosis of endometriosis. CONCLUSIONS: These findings suggest that the characteristics of sperm binding to tubal epithelium may be disrupted in women with a gynaecological pathology such as endometriosis. It is suggested that this may have the potential to interfere with the availability of freely motile spermatozoa, of the appropriate physiological status, to take part in fertilization. This may be a newly described mechanism by which endometriosis can cause infertility.

Does the Arg-Gly-Asp (RGD) adhesion sequence play a role in mediating sperm interaction with the human endosalpinx?

BACKGROUND: Sperm from several species, including the human, make direct contact with the endosalpinx. Although this is known to be beneficial to sperm function, the specific mechanisms mediating the adhesion are poorly understood. METHODS: Short linear oligopeptides containing the amino acid sequence Arg-Gly-Asp (RGD) or a scrambled sequence (GRGES) were incorporated into an established sperm-endosalpingeal binding assay. In addition, the ability of fluorescent latex beads coated with an RGD oligopeptide to bind specifically to sperm and/or epithelium was also determined. RESULTS: Significantly fewer sperm associated per field of isthmic epithelium in the presence of 62.5 micro mol/l GRGDTP (1.18 +/- 0.41; mean +/- SEM, P < 0.05) and 250 micro mol/l RGDV (1.17 +/- 0.29; P < 0.01) compared with the control incubation (3.34 +/- 0.45). There was no difference in sperm binding to ampullary epithelium in the presence of any of the oligopeptides tested. Moreover, no beads were observed bound to sperm whereas significantly more RGD-coupled beads bound to isthmic epithelium compared with ampullary epithelium (1.47 +/- 0.26 versus 0.72 +/- 0.16 P < 0.01) and this increased in a dose-dependent manner. CONCLUSIONS: These findings indicate that the recognition between the RGD sequence and integrin receptors may contribute to the interaction between sperm and the human endosalpinx in the isthmic but not in the ampullary region of the uterine tube.

Cord blood progenitor cells have greater transendothelial migratory activity and increased responses to SDF-1 and MIP-3beta compared with mobilized adult progenitor cells.

When cord blood is used as a source of haemopoietic stem cells for transplantation, fewer cells are required per kg of recipient. This greater engraftment efficiency of cord blood cells may relate to an increased ability to traverse sinusoidal endothelium, a crucial step in the homing of stem cells. We report that freshly isolated cord blood progenitors migrated more efficiently than mobilized adult cells. Cord blood progenitors responded rapidly to growth factor stimulation with an increase in migratory ability within 24 h whereas mobilized adult cells responded only after 72 h (P < 0.01). Cord blood cells also exited G0/G1 rapidly; after 24 h of growth factor exposure, 20.2 +/- 1.2% of cord blood CD34+ cells were in S + G2/M compared to 6.9 +/- 1.2% of adult CD34+ cells (P < 0.01). Proliferating CFC migrated more efficiently (13.3 +/- 3.4% for GM-CFC) than non-proliferating CFC (1.4 +/- 0.5%, P < 0.01) as determined using a 3H-thymidine suicide assay. Cord blood progenitor cells also demonstrated a greater transmigratory response to chemokine stimulation compared with adult cells; this was manifested as a differential response of freshly isolated cells to SDF-1, and of growth factor activated cells to MIP-3beta. Finally, cord blood CD34+ cells express higher levels of the chemokine receptor for SDF-1, CXCR4, when compared with mobilized adult CD34+ cells (P < 0. 05).

Relative bioavailability of danazol in dogs from liquid-filled hard gelatin capsules.

Danazol was dissolved in non-aqueous mixtures containing either polyethylene glycol 400 or polysorbate 80, and filled into hard gelatin capsules at 50 mg concentrations. The bioavailability of these formulations was compared with commercial danazol capsules in a two-way crossover study using young female beagle dogs. Both formulations showed greater oral bioavailability when compared with either the 100 or 200 mg commercial brand of danazol. The bioavailability of the polyethylene glycol 400 and polysorbate 80 formulations was enhanced 3.7 and 15.8 times, respectively, when compared at the 100 mg dose level.

Comparison of flow and laser scanning cytometry for the assay of cell proliferation in human solid tumors.

The introduction of the laser scanning cytometer offers new capabilities in cell proliferation research, through its capacity for validation of each and every cell event through direct visualization on the microscope slide. In this study, we report a direct comparison of proliferation data derived from flow and laser scanning cytometry of human tumor nuclei labeled in vivo with bromodeoxyuridine (BrdUrd). Nuclear suspensions from 19 invasive ductal breast carcinomas and 12 gastric adenocarcinomas were prepared and analysed for BrdUrd uptake and DNA content. Specimens were analysed using a FACScan and then prepared on cytocentrifuge preparations for laser scanning cytometry. DNA index, labeling index (LI), duration of S-phase (Ts) and potential doubling time (Tpot) were calculated using standard procedures. There was an excellent correlation between the two techniques in the calculation of DNA index (R = 0.983, P > 0.0001) and LI (R = 0.924, P > 0.0001). The Ts proved more problematical (R = 0.448, P = 0.0115) but the Tpot showed closer agreement (R = 0.851, P > 0.0001) as the LI was the dominant determinant of Tpot. No single parameter could be identified as the major source of variation between the two techniques. We conclude that the laser scanning cytometer produces data equivalent to that obtained by flow cytometry.

New technology in the analytical cell sciences: the laser scanning cytometer.

New technologies are making a major contribution to progress in applied clinical research in surgical oncology. The laser scanning cytometer is a new machine which combines the analytical capabilities of flow cytometry with the ability to inspect and visualize labelled cells and particles. This substantially reduces the uncertainty associated with assays in a wide range of surgical oncology research applications. This article introduces this new technology.

A parametric variation of delayed reinforcement in infants.

This study is an exploration of the parameters of delayed reinforcement with 6 infants (2 to 6 months old) in two experiments using single-subject repeated-reversal designs. In Experiment 1, unsignaled 3-s delayed reinforcement was used to increase infant vocalization rate when compared to a differential-reinforcement-of-other-than-vocalization condition and a yoked, no-contingency comparison condition. In Experiment 2, unsignaled 5-s delayed reinforcement was used to increase infant vocalization rate when compared to an alternating-treatments comparison condition. The alternating-treatments comparison consisted of 3-min components of differential reinforcement of other behavior and 3-min components of a nontreatment baseline. Successful conditioning was obtained in both experiments. These results contrast with those of previous infancy researchers who did not obtained conditioning with delays of 3 s and who attributed their findings to the limitations of the infant's memory capacity. We present an alternative conceptual framework and methodology for the analysis of delayed reinforcement in infants.

Effects of delayed reinforcement on infant vocalization rate.

Three previous studies have failed to demonstrate conditioning in infants using a 3-s delay of reinforcement. The effects of a delayed reinforcement schedule on vocalization rates therefore were explored in a single-subject repeated-reversal experimental design for 3 4- to 6-month-old normally developing infants. Each infant received delayed social reinforcement from his or her parent for vocalizing. The comparison condition was a schedule of differential reinforcement of behavior other than vocalizations to control for elicitation by social stimulation. An operant level of infant vocalizations was the initial condition, after which the differential reinforcement schedule was implemented in an across-subjects multiple baseline design. Infants' vocalization rates increased above levels measured during differential reinforcement following onset of the delayed reinforcement condition. Also, vocalization rates decreased during differential reinforcement compared to operant levels. The successful use of delayed reinforcement schedules with infants in this study, as opposed to others, is discussed in terms of procedural differences among them.

Generalized vocal imitation in infants.

Effects of modeling and response-contingent social praise on the vocal imitation of three 9- to 13-month-old infants were analyzed. Three infants and parents participated in 2 to 4 experimental sessions a week for 2 to 4 months. During each 20-min-long session, the parent presented vocal models for the infant to imitate. During the model-alone condition, no social praise was programmed for infant imitation. During the model-and-praise condition, social praise was provided by the parent for infant imitation on training trials, but not probe trials. All three infants showed systematic increases in matching during training trials following the introduction of the model-and-praise condition. Although matching during probe trials was not directly reinforced, probe-trial responding increased systematically with training-trial responding. Furthermore, non-matching infant vocalizations did not increase systematically with the introduction of the model-and-praise procedure. Together these findings provide a demonstration of generalized vocal imitation in infants, a population in which it had not previously been shown to occur.

Biliary secretion of organic anions in the dog: association with defined lipid particles.

Organic anions have recently been found to partition in vitro into various biliary lipid particulate species according to their relative hydrophobicities. To establish the physiological relevance of these observations, we intravenously injected various radiolabeled organic anions and assessed the distributions of parent compounds and their metabolites to lipid particles in canine bile. Partitioning into various biliary lipid particles was determined by gel permeation chromatography. Relative hydrophobicities of the various organic anions and their radiolabeled conjugates were determined by reverse-phase high-pressure liquid chromatography. A strong positive correlation (P less than 0.001) was found between percent vesicular association and degree of hydrophobicity for a given organic anion and/or its more polar conjugate. We conclude that 1) the hydrophobic-hydrophilic balance of organic anions is a key factor governing their partitioning to lipid particles secreted in bile; 2) the present study agrees well with our previously published in vitro observations; and 3) other chemical constituents, e.g., proteins, mucin, etc., appear to have little or no effect on organic anion transport in bile.

Alcohol metabolism and toxicity: role of cytochrome P-450.

A new isozyme of cytochrome P-450, designated from 3a on the basis of its relative electrophoretic mobility, has been purified to homogeneity from liver microsomes of rabbits treated chronically with ethanol. This cytochrome has the highest activity of the known rabbit P-450 isozymes in the oxidation of ethanol to acetaldehyde. In view of the reports of others that the hepatotoxicity of acetaminophen is increased in ethanol-treated animals and the human alcoholic, we have determined the activity of the six available P-450 isozymes in the activation of the drug to give an intermediate which forms a conjugate with reduced glutathione. Isozyme 3a, 4, and 6, the three major forms of cytochrome P-450 present in liver microsomes from rabbits chronically treated with ethanol, exhibited the highest activities in the reconstituted enzyme system, whereas isozymes 3b and 3c were 10- to 20-fold less effective and phenobarbital-inducible isozyme 2 was essentially inactive, even in the presence of cytochrome b5. The results obtained thus indicate that induction by ethanol of P-450 isozyme 3a may contribute to the toxicity of acetaminophen but that other cytochromes also play a significant role.

Studies on the site of 1,25-dihydroxyvitamin D3 synthesis in vivo.

Anephric, vitamin D-deficient male rats were injected with a physiologic dose of 25-hydroxy[26,27-3H]vitamin D3 (specific activity of 160 Ci/mmol), and 18-20 h later, intestine, bone, and serum were analyzed by high performance liquid chromatography for 1,25-dihydroxy-[26,27-3H]vitamin D3. Identical studies were carried out using sham-operated rats and rats with ligated ureters. No 1,25-dihydroxy[26,27-3H]vitamin D3 was detected in the tissues from anephric rats, while large amounts were detected in sham-operated and ureteric ligated controls. This result demonstrates that in the nonpregnant rat, 1,25-dihydroxyvitamin D3 is either not synthesized or is synthesized in vanishingly small amounts in bone and intestine in vivo, casting considerable doubt of the physiological importance of reports of in vitro synthesis of 1,25-dihydroxyvitamin D3 by cells in culture derived from bone and elsewhere.

Vitamin D of human milk: identification of biologically active forms.

Human milk has been found to contain 40 to 50 IU/l of vitamin D activity. This was determined by measuring stimulation of intestinal calcium transport in the rat, an assay not subject to the errors inherent in the rat line test or calcification assay. Five vitamin D metabolites were then isolated using a combination of conventional chromatography on Sephadex LH-20 and Lipidex 5000 followed by high-performance liquid chromatography. 24,25-Dihydroxyvitamin D and 1,25-dihydroxyvitamin D were measured using binding protein assays and were found to be present at very low levels. These dihydroxylated metabolites do not contribute significantly to the total vitamin D activity. Vitamins D2 and D3 were found to be present at concentrations of 338 and 41 ng/l, respectively. This is equivalent to 14 to 16 IU/l of vitamin D activity. Human milk contains 163 ng/l of 25-hydroxyvitamin D3, which gives about 33 IU/l of vitamin D activity. Thus 25-hydroxyvitamin D3 accounts for about 75% of the biological activity observed in the calcium transport assay. Vitamin D2, vitamin D3, and 25-hydroxyvitamin D3 are responsible for more than 90% of the total vitamin D activity present. This fails to support the idea that vitamin D-sulfate or any other unknown metabolites of vitamin D provide significant vitamin D activity in human milk.

Vitamin D compounds in cows' milk.

The milk from cows fed normal levels of vitamin D has been found to contain approximately 40 IU per liter of vitamin D activity. A 14-fold increase in dietary vitamin D intake causes only a doubling of the amount of vitamin D in milk. This was determined by measuring stimulation of intestinal calcium transport in the vitamin D-deficient rat. Four vitamin D compounds were then isolated from cow's milk using a combination of conventional chromatography on Sephadex LH-20 and Lipidex 5000 followed by high-performance liquid chromatography. 24,25-Dihydroxycholecalciferol and 1,25-dihydroxycholecalciferol were measured using binding protein assays. One liter of milk contained 27 ng and 4.9 ng, respectively, of these two metabolites. Together these account for about 15% of the vitamin D activity. Cholecalciferol was found to be present at a concentration of 281 ng/liter or 11 IU/liter of biological activity. The milk contained 145 ng/liter 25-hydroxycholecalciferol or 29 IU/liter of activity. Therefore the known vitamin D compounds fully account for the biological activity observed in milk. It is therefore clear that no evidence could be found for the existence of a highly active water-soluble form of vitamin D in milk.

Synthesis and biological activity of vitamin D3-sulfate.

Vitamin D3-3 beta-sulfate has been synthesized using pyridine sulfur trioxide as the sulfate donor. It has been shown to be pure by high performance liquid chromatography and spectral methods. Unlike previous reports, the product has been identified unambiguously as the 3 beta-sulfate ester of vitamin D3 by its ultraviolet, nuclear magnetic resonance, infrared, and mass spectra. The biological activity of vitamin D3-sulfate was then determined in vitamin D-deficient rats. Vitamin D3-sulfate has less than 5% of the activity of vitamin D3 to mobilize calcium from bone and approximately 1% of the ability of vitamin D3 to stimulate calcium transport, elevate serum phosphorus, or support bone calcification. These results disprove previous claims that vitamin D3-sulfate has potent biological activity, and they further do not support the contention that vitamin D-sulfate represents a potent water-soluble form of vitamin D in milk.

Solanum glaucophyllum as source of 1,25-dihydroxyvitamin D3.

Vitamin D-deficient rats given an aqueous extract of the South American plant Solanum glaucophyllum accumulate 1,25-dihydroxyvitamin D3 in their blood and intestines at the time they show enhanced intestinal calcium absorption. The identity of the 1,25-dihydroxyvitamin D3 was established by co-chromatography with 1,25-dihydroxy[23,24-3H]vitamin D3 on Sephadex LH-20 columns, microparticulate silica gel columns, a reversed-phase column developed under high pressure, and by a specific 1,25-dihydroxyvitamin D3 binding assay. The chromatographic systems used are fully capable of resolving all of the known metabolites of vitamin D3. Serum of the S. glaucophyllum-treated rats showed 300 pg/ml of 1,25-dihydroxyvitamin D3 and no detectable 1,25-dihydroxyvitamin D2. Similarly, intestine of such rats had 230 pg/g of 1,25-dihydroxyvitamin D3. Control animals which received the vehicle instead of S. glaucophyllum had only 20 pg/ml of 1,25-dihydroxyvitamin D3 in their serum and 4.4 pg/g of 1,25-dihydroxyvitamin D2 in their intestine. These results demonstrate that S. glaucophyllum extracts must be a source of 1,25-dihydroxyvitamin D3; thus a significant basis for the calcinogenic properties of S. glaucophyllum must be the presence of a conjugated form of 1,25-dihydroxyvitamin D3, which is rendered available by digestion.