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Biomedical subjects

R A Polin

Publications and source records attributed to R A Polin.

At least 19 recordsLinked to original sources

Effects of a night-float system on resident activities and parent satisfaction.

Night-float systems have recently been proposed as a way to reduce resident stress resulting from irregular sleep patterns. We prospectively evaluated the effects of a night-float system in which designated residents relieved on-call senior residents and interns of routine admissions of patients in medically stable condition during the late-night period (11 PM to 7 AM). Senior residents (3.7 vs 2.4 hours) and interns (3.7 vs 3.2 hours) reported sleeping more under the night-float system than under the traditional system. The night-float system did not affect residents' overall ratings of call nights. Educators who reviewed medical records agreed with residents' decisions about patients' appropriateness for admission using the night-float system in 95 (81%) of 117 cases. When educators disagreed with residents, the most common reasons were the patient's potential educational value or medical instability. The night-float system did not affect interns' ratings of the educational value of late-night admissions or parents' ratings of satisfaction with medical care. We conclude that the night-float system can increase resident sleep with little cost to parent satisfaction, but standards for selective use may be needed to avoid compromising patient care and resident education.

Consumer Behavior

Sodium restriction versus daily maintenance replacement in very low birth weight premature neonates: a randomized, blind therapeutic trial.

To test the hypothesis that restriction of sodium intake during the first 3 to 5 days of life will prevent the occurrence of hypernatremia and the need for administration of large fluid volumes, we prospectively and randomly assigned 17 babies (mean +/- SD: 850 +/- 120 gm; 27 +/- 1 weeks of gestation) to receive in blind fashion either daily maintenance sodium or salt restriction with physician-prescribed parenteral fluid intake. Maintenance-group infants received 3 to 4 mEq of sodium per kilogram per day; restricted infants received no sodium supplement other than with such treatments as transfusion. Sodium balance studies conducted for 5 days demonstrated that maintenance salt intake resulted in a daily sodium balance near zero, whereas sodium-restricted infants continued to excrete urinary sodium at a high rate, which promoted a more negative balance (average daily sodium balance -0.30 +/- 1.78 SD in maintenance group vs -3.71 +/- 1.47 mEq/kg per day in restriction group; p less than 0.001). Care givers tended to prescribe daily increases in parenteral fluids for the salt-supplemented infants, perhaps because serum sodium concentrations were elevated in these infants after the first day of the study (p less than 0.001). Hypernatremia developed in two sodium-supplemented infants (greater than 150 mEq/L), and hyponatremia developed in two sodium-restricted infants (less than 130 mEq/L); however, the restricted infants were more likely to have normal serum osmolality (p less than 0.05). Both groups of infants produced urine that was neither concentrated nor dilute, with a high fractional excretion of sodium; renal failure was not observed. The mortality rate was not affected, but the incidence of bronchopulmonary dysplasia was significantly less in the sodium-restricted babies (p less than 0.02). We conclude that in tiny premature infants, a fluid regimen that restricts sodium may simplify parenteral fluid therapy targeted to prevent hypernatremia and excessive administration of parenteral fluids.

Fluid Therapy

Adherence of human newborn infants' monocytes to matrix-bound fibronectin.

The localization of monocytes to sites of inflammation is mediated by interactions with extracellular matrix components including fibronectin, a nonimmune opsonin with binding sites for collagen, fibrin, heparin, and cell surfaces. This study demonstrates that newborn infants' monocytes bind to both gelatin (i.e., denatured collagen) and matrix-bound fibronectin to a degree comparable to that of adult-derived cells.

Adult

Infection of cord blood monocyte-derived macrophages with human immunodeficiency virus type 1.

We have investigated the susceptibility of cord blood monocyte-derived macrophages to human immunodeficiency virus type 1 (HIV-1) infection in vitro. Cord blood monocytes were maintained in vitro for 10 to 15 days and then infected with HIV-1. Syncytia were observed 14 days after infection by light microscopy. Viral proteins were detected by immunofluorescence assay. Electron microscopic examination demonstrated typical lentivirus particles within cytoplasmic vacuoles. The supernatants from the HIV-1-infected cultures also contained significant reverse transcriptase activity and p24 antigen. Like adult monocyte/macrophages, cord-derived monocyte/macrophages expressed the CD4 receptor molecule. Pretreatment with blocking antibody prior to infection with HIV-1 Bal significantly reduced or blocked infection of cord monocyte/macrophages. When cord and adult monocyte/macrophages were infected with HIV-1 Bal or Ada-M and directly compared, higher reverse transcriptase activities and p24 antigen expression were obtained with cord monocyte/macrophages. However, no significant difference was found between adult and cord monocyte/macrophages infected with HIV-1 IIIB. These observations suggest that cord monocyte-derived macrophages may be important in the pathogenesis of pediatric AIDS and that the increased susceptibility of cord monocyte/macrophages to HIV-1 infection in vitro may be relevant to the enhanced susceptibility of neonates to HIV-1 diseases in vivo.

Adult

Induction of monocytic cell adherence to matrix-bound fibronectin by phorbol ester.

The inflammatory response requires the localization of monocytic cells to sites of tissue injury through adherence to extracellular matrix molecules such as fibronectin (Fn), a nonimmune opsonin, which binds to collagen, fibrin, heparin and cell surfaces. Adherence to this molecule of two myeloid cell lines differing in their stage of differentiation, was studied. In the baseline state, U937 monocytic cells bound specifically to matrix-bound Fn, while HL-60 promyelocytic cells bound minimally. Exposure to Phorbol myristate acetate (PMA) dramatically increased binding of both U937 and HL-60 cells to Fn with plateau effects at 10 ng/ml for both cell lines and at 30 and 60 minutes for U937 and HL-60, respectively. Treatment with metabolic inhibitors suggests that PMA stimulation depends at least in part on intact energy metabolism, protein synthesis and cytoskeletal components. This system should help elucidate the early molecular and biochemical events involved in monocyte adherence to the extracellular matrix.

Cell Adhesion

Neonatal sepsis.

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Antibodies, Bacterial

Effects of indomethacin and prostaglandin E1 on the production of fibronectin and lysozyme by monocyte-derived macrophages in vitro.

Fibronectin secreted by macrophages may contribute to the development of pulmonary fibrosis. Prostaglandins are important regulators of macrophage metabolism whose role in the regulation of fibronectin production is not known. In this study, we examined the effects of PGE1 and indomethacin on human monocyte-derived macrophages exposed to these agents in culture for 10 to 14 days. Indomethacin (10 micrograms/ml) reduced the ratio of supernatant fibronectin to adherent cell DNA by 32%, p < 0.01, and reduced lysozyme/DNA by 29%, p < 0.0001. Exogenous PGE1 (1 ng/ml) did not affect fibronectin, but increased lysozyme/DNA by 27%, p < 0.01. In additional experiments, supernatant fibronectin and total protein synthesized in the presence of 3H-leucine were measured. Indomethacin (10 micrograms/ml) had no effect on total supernatant protein radioactivity, but reduced fibronectin/DNA by 33%, p < 0.001, and reduced fibronectin/total protein by 19%, p < 0.01. Since indomethacin increases macrophage secretion of plasminogen activator and interleukin-1, these experiments add to the evidence that specific secretory products of macrophages are regulated independently. We conclude that indomethacin at 10 micrograms/ml decreases the production of fibronectin and lysozyme by monocyte-derived macrophages. The modest size of the effect, and its absence at lower doses of indomethacin, indicate that prostaglandins are unlikely to have a major role in the regulation of macrophage production of fibronectin.

Adult

Lipopolysaccharide enhances monocyte adherence to matrix-bound fibronectin.

Fibronectin (Fn), an extracellular matrix glycoprotein with binding sites for collagen, fibrin, heparin, and cell surfaces, is a nonimmune opsonin which up-regulates phagocytic function and facilitates adherence of human monocytes. We have developed a simple assay to study adherence of peripheral blood monocytes to Fn on a gelatin matrix. While cell adherence was enhanced by the presence of Fn in a dose-dependent manner, it was inhibited by peptides containing the Arg-Gly-Asp (RGD) cell attachment sequence or by coating the matrix with antibodies directed against Fn. Preincubation of monocytes for 30 min with Escherichia coli lipopolysaccharide (LPS) at doses of 1-50 micrograms/ml increased adherence to Fn-gelatin but not to gelatin alone, while longer preincubation (24 hr) resulted in similar changes at lower doses (0.01-1.0 micrograms/ml). Enhanced Fn adherence may be essential for monocyte localization to sites of inflammation.

Antineoplastic Agents

Management of neonatal hyperbilirubinemia: rational use of phototherapy.

Phototherapy has been used to treat neonatal hyperbilirubinemia for more than three decades; however, it is only during the last ten years that an understanding of the mechanism of action of phototherapy has emerged. While visible light is known to photooxidize and photoisomerize bilirubin, recent data suggest that the formation of bilirubin structural isomers (lumirubin) is responsible for the decrement in serum bilirubin. This paper discusses current clinical recommendations for light dosage and wavelength and develops new guidelines based upon recent information of how light effects a reduction in the serum bilirubin concentration.

Bilirubin

Expression of the complement receptors CR1 and CR3 and the type III Fc gamma receptor on neutrophils from newborn infants and from fetuses with Rh disease.

Developmental defects in neutrophil function, including diminished expression of plasma membrane receptors, may play an important role in the susceptibility of the newborn infant to infection. We used monoclonal antibodies and flow cytometry to study the expression of complement receptor type one (CR1), complement receptor type three (CR3), and Fc gamma receptor type three (FcRIII) on neutrophils from six fetuses with Rh disease, 10 preterm infants, nine term infants, and nine adults. Expression of the complement receptors on unstimulated cells was similar for all groups, but significant differences in complement receptor expression were observed after stimulation with N-formyl-methionyl-leucyl-phenylalanine (FMLP). Fetal, preterm, and term infant neutrophils expressed less CR3 than FMLP-stimulated neutrophils of adults [61 +/- 2, 48 +/- 4, and 66 +/- 4% (mean +/- SEM) of the mean for adults, p less than 0.05]. FMLP-stimulated CR1 expression for these groups was 61 +/- 6, 73 +/- 6, and 91 +/- 9% of the adult mean (p less than 0.05, fetal versus term infant and adult). Expression of both CR3 and CR1 increased with postconceptional age in the infants (r2 = 0.49, p less than 0.001 for CR3; r2 = 0.23, p less than 0.05 for CR1). Neutrophils of the preterm and term infants expressed less FcRIII than adult neutrophils (68 +/- 10 and 77 +/- 7% of the adult mean, p less than 0.05, for FMLP-stimulated cells), whereas fetal neutrophil FcRIII expression did not differ from that of the adult.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, Differentiation

Half-dose immunization for diphtheria, tetanus, pertussis: response of preterm infants.

The American Academy of Pediatrics currently recommends administering full-dose diphtheria, tetanus, pertussis, (DTP) vaccine to preterm infants, beginning at 2 months' chronologic age. Many physicians, however, continue to administer DTP vaccine at a reduced dosage in an attempt to lessen side effects. This study was designed to quantitate the immune response of 20 preterm infants immunized with half-dose DTP vaccine and to determine the nature and extent of side effects. Control subjects were 25 preterm infants immunized with full-dose vaccine. Although 96% of infants who received a full dose were able to mount a serologic response to pertussis after a second dose of DTP, 45% of infants who received a half dose were unable to mount a similar immune response to pertussis even after a third dose of DTP and required a full-dose (fourth dose of DTP) vaccine to better ensure protection. Serologic responses to diphtheria and tetanus were similar in the two groups. The incidence of side effects in preterm infants receiving both full-dose and half-dose DTP was less than that seen in a full-term population. Thus, the physician caring for the preterm infant should adhere to the American Academy of Pediatrics' recommendation for the immunization of preterm infants and offer full-dose DTP vaccine at the routine time intervals of 2, 4, 6, and 15 or 18 months' chronologic age to ensure adequate protection.

Antibodies, Bacterial

Effects of dexamethasone and indomethacin on elastase, alpha 1-proteinase inhibitor, and fibronectin in bronchoalveolar lavage fluid from neonates.

Elastase activity and concentrations of alpha 1-proteinase inhibitor, albumin, and fibronectin were measured in bronchoaleolar lavage (BAL) fluid from ventilated lungs in preterm neonates with lung disease before and after treatment with dexamethasone or indomethacin. Treatment with dexamethasone was associated with a significant decrease in BAL elastase activity but no change in fibronectin, albumin, or alpha 1-proteinase inhibitor concentrations. In contrast, treatment with indomethacin was associated with an increase in BAL elastase activity and fibronectin concentration, with no change in albumin or alpha 1-proteinase inhibitor concentrations. Control groups showed no changes in these BAL fluid biochemical markers during a similar time period. These data indicate that treatment with corticosteroids decreases lung inflammation as measured by BAL elastase activity. Corticosteroid treatment may not inhibit the development of pulmonary fibrosis, because fibronectin concentrations in BAL fluid were unaffected. Indomethacin treatment may augment lung inflammation and fibrosis by increasing BAL elastase activity and fibronectin concentration.

Acute-Phase Proteins

Infant botulism.

Infant botulism is a unique neuromuscular disease affecting infants less than six months old. It is the result of intraintestinal toxin production by C. botulinum (toxi-infection). Characteristic symptoms include constipation, lethargy, and decreased feeding. Physical examination often reveals generalized hypotonia with cranial nerve impairment. Recovery is dependent on supportive care in an intensive care setting. The relationship of this disease to the sudden infant death syndrome requires further study.

Botulinum Antitoxin

Conjugated hyperbilirubinemia in infants with erythroblastosis fetalis.

In an attempt to identify the incidence of conjugated hyperbilirubinemia in infants with erythroblastosis fetalis the records of 67 infants were reviewed. Twenty-two infants were found to have direct bilirubin concentrations greater than 1.0 mg./dl. Among 11 infants who underwent intrauterine exchange transfusion, nine (82%) had conjugated hyperbilirubinemia. Of the remaining 56 infants without the procedure, only 13 (23%) showed evidence of this complication. To predict infants at risk of developing conjugated hyperbilirubinemia, the ratio of hematocrit and total bilirubin concentration in cord blood (H/B ratio) was examined.

Bilirubin

Intermediate phototherapy in the treatment of jaundice in the premature infant.

A controlled trial of the use of intermittent phototherapy for the treatment of hyperbilirubinemia in newborn infants is reported. Periods of illumination of (1) 15 minutes light on, 15 minutes light off, (2) 15 minutes on, 30 minutes off, and (3) 15 minutes on, 60 minutes off are as effective as is continuous illumunation. A comparison with previous trials of intermittent phototherapy is made and differences in results are explained using as a model the action of light on bilirubin.

Humans

Effect of bacterial flora on staphylococcal colonisation of the newborn.

The umbilical and nasopharyngeal flora of newborn infants was examined on days 3, 14, and 42 of life. An analysis of the bacteriological findings suggests that colonisation by either Staphylococcus aureus or Staph. epidermidis prevents colonisation by the other staphylococcus. Similarly, colonisation by Gram-negative bacteria prevents colonisation by staphylococci. Further, this bacterial interference lasts for as long as 42 days, which suggests the possibility of artificially colonising newborns with nonpathogens to prevent subsequent colonisation and disease by virulent microorganisms.

Humans

Staphylococcal and streptococcal colonization of the newborn infant: effect of antiseptic cord care.

A randomized controlled study was undertaken to compare the effectiveness of three umbilical cord treatment regimens in controlling neonatal bacterial colonization. The three regimens studied included castile soap, triple dye, and silver sulfadiazine. The triple dye and silver sulfadiazine application inhibited bacterial colonization. Staphylococcal colonization was inhibited by both treatment regimens but most effectively by triple dye. Group B streptococcal colonization was inhibited most effectively by silver sulfadiazine while triple dye application to the umbilicus promoted colonization with this microorganism. Silver sulfadiazine was more effective in controlling colonization with Gram-negative microorganisms.

Anti-Infective Agents, Local