Pneumococci stimulate the production of the inducible nitric oxide synthase and nitric oxide by murine macrophages

The role of nitric oxide (NO) in the pathophysiology of gram-positive sepsis is uncertain. In inflammatory conditions, high-output NO production is catalyzed by the enzyme inducible nitric oxide synthase (iNOS). The ability of 2 strains of pneumococci, pneumococcal cell wall preparations, and purified pneumococcal capsule (Pnu-Imune 23) to trigger the production of iNOS protein and NO in RAW 264.7 murine macrophages was tested. Live pneumococci, oxacillin-killed pneumococci, and pneumococcal cell wall preparations stimulated the production of iNOS and NO by RAW 264.7 cells in the presence, but not the absence, of low concentrations of recombinant murine interferon-gamma. In contrast, purified pneumococcal capsule induced little or no iNOS or NO production by these cells. Thus, pneumococci stimulate high-output NO production by murine macrophages. The potential role of NO in the pathogenesis of pneumococcal sepsis deserves further study.     

The alcohol deprivation effect in the alcohol-preferring P rat under free-drinking and operant access conditions

The alcohol-deprivation effect (ADE) was examined under 4-hr operant and 24-hr free-choice alcohol access in the alcohol-preferring (P) rat after deprivation intervals from 2 to 4 weeks. Results indicated that adult male P rats responding for 6 weeks on a concurrent FR-5/FR-1 schedule of reinforcement for alcohol and water, respectively, and then deprived of alcohol for 2 weeks, demonstrated a 40% increase in alcohol responding during the first 60 min of alcohol reinstatement. The alcohol deprivation effect was temporary, however, as responding did not differ from baseline levels on the second day of reinstatement. In a second experiment, weanling male and female P rats received 7 weeks of continuous access to alcohol, beginning at 21 days of age, and were then deprived of alcohol for 4 weeks. On the first day of alcohol reinstatement, P rats exhibited a 40% to 45% increase from baseline alcohol drinking levels, with alcohol intake returning to baseline levels by the 3rd day of reinstatement. Although alcohol intake was higher in females than in males when adjustment was made for body weight, there were no gender differences in the magnitude of the alcohol deprivation effect. Taken together, these results indicate that the ADE is a long-lasting phenomenon that occurs under both operant and continuous access conditions in the P rat, and thus these rats may be useful models for the study of factors involved in relapse of alcohol drinking.     

Decreased response to phototherapy for neonatal jaundice in breast-fed infants

OBJECTIVE: To evaluate the efficacy of phototherapy for nonhemolytic hyperbilirubinemia in breast-fed and formula-fed infants and infants receiving formula and breast milk. DESIGN: Prospective study. SETTING: Nursery for healthy infants. METHOD: Full-term healthy infants with nonhemolytic hyperbilirubinemia (bilirubin concentration, >255 micromol/L [14.9 mg/dL] or 222 micromol/L [13.0 mg/dL] at ages younger than 48 hours) were treated with conventional phototherapy by using daylight fluorescent lamps. Three groups of infants were studied: group 1, formula-fed infants; group 2, breast-fed infants; and group 3, infants receiving formula and breast milk. All patterns of feeding started at birth. Phototherapy was terminated only when bilirubin concentrations had decreased to less than 185 micromol/L (10.8 mg/dL); the minimum exposure period was 24 hours. RESULTS: A total of 163 infants were studied: group 1, 79; group 2, 34; and group 3, 50. The age at the start of exposure was comparable in all groups. The mean+/-SD weight loss as a percentage of birth weight was as follows: group 1, 2.8%+/-5.0%; group 2, 6.1%+/-3.4%; and group 3, 3.2%+/-2.6%. The duration of exposure to phototherapy was as follows: group 1, 54.1+/-20.8 hours; group 2, 64.6+/-25.1 hours; and group 3, 54.9+/-21.5 hours; the 24-hour rate of decrease in the bilirubin concentration was as follows: group 1, 18.6%+/-11.7%; group 2, 17.1%+/-9.6%; and group 3, 22.9%+/-9.4%. The overall rate of decrease in the bilirubin concentration for the duration of exposure to phototherapy was as follows: group 1, 0.8%+/-0.3% per hour; group 2, 0.6%+/-0.3% per hour; and group 3, 0.8%+/-0.3% per hour. Weight loss at the start of phototherapy was significantly greater in group 2 compared with group 1 (P<.001) and group 3 (P<.001), although the hemoglobin and hematocrit values were comparable. The duration of exposure to phototherapy was not significantly different in the 3 groups (P=.06); however, the duration of exposure of group 2 infants was 10 hours more than that of the other 2 groups. The 24-hour rate of decrease in the bilirubin concentration in group 3 was significantly better than that of group 2 (P = .007) and group 3 (P = .02); the rates of decrease for groups 2 and 3 were similar (P = .52). The overall rate of decrease in the bilirubin concentration during the duration of exposure to phototherapy in group 2 was significantly less than that of group 1 (P = .002) and group 3 (P<.001); the rates for groups 1 and 3 were similar (P = .35). The postexposure rebound bilirubin concentrations were comparable in all groups during the first 2 days; however, the duration of moderate jaundice in group 2 was more prolonged. CONCLUSIONS: The response to phototherapy of group 2 infants was significantly slower than that of group 3 and group 1 infants; this response was still of adequate efficacy. The addition of formula to the feedings for totally breast-fed infants, without suspension of breast-feeding, would enhance the efficacy of phototherapy and reduce exposure time.     

Exploring the potential of problem-based learning in nurse education

Despite the increased attention that problem-based learning has received as an appropriate pedagogical technique for educating adults for professional practice, reports that evaluate the process are rare and usually relate to professions other than nursing. A study was undertaken in order to discover the graduates' own perceptions of a problem-based learning programme and its effectiveness in preparing them for the reality of their chosen profession. Twelve practising graduate nurses who had completed the programme were interviewed according to the ethnographic method. Three categories were identified from the data: 'and all of a sudden...', which describes the transition from PBL student to staff nurse; 'not an unthinking assistant', where the characteristics that the PBL graduates believe make them different from traditionally trained nurses are described; and 'the buck stops here', which describes the sense of personal responsibility that the graduates experience in terms of their learning and actions.     

Protein thermostability above 100 degreesC: a key role for ionic interactions

The discovery of hyperthermophilic microorganisms and the analysis of hyperthermostable enzymes has established the fact that multisubunit enzymes can survive for prolonged periods at temperatures above 100 degreesC. We have carried out homology-based modeling and direct structure comparison on the hexameric glutamate dehydrogenases from the hyperthermophiles Pyrococcus furiosus and Thermococcus litoralis whose optimal growth temperatures are 100 degreesC and 88 degreesC, respectively, to determine key stabilizing features. These enzymes, which are 87% homologous, differ 16-fold in thermal stability at 104 degreesC. We observed that an intersubunit ion-pair network was substantially reduced in the less stable enzyme from T. litoralis, and two residues were then altered to restore these interactions. The single mutations both had adverse effects on the thermostability of the protein. However, with both mutations in place, we observed a fourfold improvement of stability at 104 degreesC over the wild-type enzyme. The catalytic properties of the enzymes were unaffected by the mutations. These results suggest that extensive ion-pair networks may provide a general strategy for manipulating enzyme thermostability of multisubunit enzymes. However, this study emphasizes the importance of the exact local environment of a residue in determining its effects on stability.     

The biology of leptin: a review

Leptin, a 16-kDa protein secreted from white adipocytes, has been implicated in the regulation of food intake, energy expenditure, and whole-body energy balance in rodents and humans. The gene encoding leptin was identified by positional cloning and is the mutation leading to the profound obese phenotype of the ob/ob mouse. Exogenous administration of leptin to ob/ob mice leads to a significant improvement in reproductive and endocrine status as well as reduced food intake and weight loss. The expression and secretion of leptin is highly correlated with body fat mass and adipocyte size. Cortisol and insulin are potent stimulators of leptin expression, and expression is attenuated by beta-adrenergic agonists, cAMP, and thiazolidinediones. The role of other hormones and growth factors in the regulation of leptin expression and secretion is emerging. Leptin circulates specifically bound to proteins in serum, which may regulate its half-life and biological activity. Isoforms of the leptin receptor, members of the interleukin-6 cytokine family of receptors, are found in multiple tissues, including the brain. Many of leptin's effects on food intake and energy expenditure are thought to be mediated centrally via neurotransmitters such as neuropeptide Y. Multiple peripheral effects of leptin have also been recently described, including the regulation of insulin secretion by pancreatic beta cells and regulation of insulin action and energy metabolism in adipocytes and skeletal muscle. Leptin is thought to be a metabolic signal that regulates nutritional status effects on reproductive function. Leptin also plays a major role in hematopoeisis and in the anorexia accompanying an acute cytokine challenge. The profound effects of leptin on regulating body energy balance make it a prime candidate for drug therapies for humans and animals.     

Group B streptococcal bacteremia in adults. Five years' experience and a review of the literature

The importance of group B streptococcus (GBS) as a cause of serious infectious disease among adults is not widely appreciated. In adults, the modes of acquisition and transmission are unknown. Since most hospital-based studies of GBS bacteremia in adults consist of small numbers of patients, the clinical spectrum of disease is not well described. Our retrospective study reviews the clinical features, antimicrobial therapy, and risk factors for mortality of 32 adult patients (18 women and 14 men) with GBS bacteremia and compares the proportion of isolates from the different beta-hemolytic streptococci sero-groups. We found that 39% of isolates from adult blood cultures were group B, a frequency nearly identical to that of group A streptococcal bacteremia. Most (66%) adult patients were more than 50 years old. Primary bacteremia was the most frequent clinical diagnosis, occurring in 7 (22%) of 32 patients. Nonhematologic cancer was the most frequently associated condition (25%). Nineteen percent of the patients had diabetes mellitus. The overall mortality rate was 31% and was significantly associated with increasing age. Our results are compared to those obtained by a review of all 5 previous comparable studies and demonstrate that GBS bacteremia is a serious infection in adults with increased mortality related to advancing age.     

Mammalian and Drosophila dachshund genes are related to the Ski proto-oncogene and are expressed in eye and limb

The human myeloid leukemias are a diverse group of disorders characterized by massive clonal expansion of myeloid cells showing variable degrees of differentiation block. Leukemic dendritic cells were generated in culture from chronic myelogenous leukemia (CML). These were used to stimulate autologous T cells to develop leukemia-specific cytotoxicity. Available data suggest that the cells responsible for the cytolytic activity are at least in part CD8+ and HLA restricted in their function. Additional data suggest that some anti-CML cellular activity may be Fas mediated. T-cell receptor studies provide evidence for an oligoclonal response implying a recognition of a limited number of antigens. We have used culture techniques similar to those used for CML to study the ability of AML cells to differentiate toward dendritic cells. Four of five patients have shown acute leukemia-derived dendritic cells. This work offers an avenue for the development of novel strategies for the control of human myeloid leukemias.     

Secondary membranoproliferative glomerulonephritis due to hemolytic uremic syndrome: an unusual presentation

In vitro selection can be used to generate nucleic acid ligands (aptamers) to target molecules ranging in size and structure from cations to cells. However, the selection process is repetitive and time-consuming. We have automated a protocol for in vitro selection using an augmented Beckman Biomek 2000 pipetting robot. The automated selection procedure requires the integration of four devices and the optimization of four molecular biology methods, and is one of the most complex automated protocols attempted to date. Initial attempts at selection yielded robust replication parasites, but optimization of the automated selection procedure suppressed the emergence of these parasites and led to the selection of true nucleic acid ligands. Automated selection can now be used to generate nucleic acid aptamers in days rather than weeks or months.