Changes in the nuclei of astrocytes following portacaval shunting and portacaval transposition in the rat.

Structural abnormalities are found in the astrocytes of the dentate nuclei of animals after portacaval shunting (PCS). These changes are also found in man in association with portal-systemic encephalopathy. To investigate the relationship between portal-systemic shunting and hepatocellular dysfunction in the pathogenesis of these changes, PCS and protacaval transposition (PCT) were performed in rats. PCT diverts portal blood into the systemic circulation, but retains normal total hepatic blood flow by perfusion with systemic venous blood. Liver function and mass are better preserved than after PCS. Abnormal glial cells were found in 4.03% of animals following sham operation, 13.45% following PCT, and 19.09% following PCS. Both experimental groups differed significantly from control animals, and the number of abnormal cells was significantly higher after PCS than after PCT. These findings are in keeping with the hypothesis that hepatocellular dysfunction plays an important role in addition to portal-systemic shunting in the aetiology of the structural changes in the brain associated with hepatic encephalopathy.     

Mycobacterium-induced potentiation of type 1 immune responses and protection against malaria are host specific

Malaria and tuberculosis are endemic in many regions of the world, and coinfection with the two pathogens is common. In this study, we examined the effects of long- and short-term infection with Mycobacterium tuberculosis on the course of a lethal form of murine malaria in resistant (C57BL/6) and susceptible (BALB/c) mice. C57BL/6 mice coinfected with M. tuberculosis CDC1551 and Plasmodium yoelii 17XL had a lower peak parasitemia and increased survival compared to mice infected with P. yoelii 17XL alone. Splenic microarray analysis demonstrated potentiation of type 1 immune responses in coinfected C57BL/6 mice, which was especially prominent 5 days after infection with P. yoelii 17XL. Splenocytes from coinfected C57BL/6 mice produced higher levels of gamma interferon (IFN-gamma) and tumor necrosis factor alpha than splenocytes from mice infected with either pathogen alone. Interestingly, mycobacterium-induced protection against lethal P. yoelii is mouse strain specific. BALB/c mice were significantly more susceptible than C57BL/6 mice to infection with P. yoelii 17XL and were not protected against lethal malaria by coinfection with M. tuberculosis. In addition, M. tuberculosis did not augment IFN-gamma responses in BALB/c mice subsequently infected with P. yoelii 17XL. These data indicate that M. tuberculosis-induced potentiation of type 1 immune responses is associated with protection against lethal murine malaria.     

Interaction of Inflammatory Cells and Oral Microorganisms VII. In Vitro Polymorphonuclear Responses to Viable Bacteria and to Subcellular Components of Avirulent and Virulent Strains of Actinomyces viscosus

Both virulent (V) and avirulent (AV) strains of Actinomyces viscosus T14 are capable of colonizing the oral cavity of gnotobiotic rats, but only T14-V causes destructive periodontal disease. The basis for this difference in in vivo pathogenicity has not been adequately defined. In the present study we compared the capacities of T14-AV and T14-V to provoke in vitro extracellular release of lysosomal constituents from human polymorphonuclear leukocytes (PMNs). In serum-free cultures, viable T14-V but not T14-AV stimulated discharge of PMN lysosomes. The release response was correlated with PMN phagocytic activity; thus, PMNs readily ingested T14-V but not T14-AV. To explain these differences in PMN-bacteria interactions, subcellular fractions of T14-AV or T14-V were incubated with PMNs. A crude, insoluble sonic extract derived from T14-V caused PMN lysosome release, but a similar fraction from T14-AV was inactive. However, following extensive washing and treatment with deoxyribonuclease or sodium dodecyl sulfate, cell wall fractions of T14-AV stimulated lysosome release. These procedures apparently removed an extracellular polysaccharide slime which is synthesized by T14-AV but not by T14-V. There was a significant reduction in the capacities of viable T14-V or cell wall fractions of T14-V or T14-AV to provoke PMN lysosome release when these agents were preincubated with a slime material isolated from T14-AV. This inhibitory influence of slime was overcome by the addition of fresh or heated (56°C, 30 min) serum to the PMN-bacteria cultures. The data suggest a relationship between the abilities of the avirulent and virulent strains of A. viscosus T14 to act as periodontal pathogens in vivo and to serve as stimuli for PMN lysosome release in vitro.     

Inpatient β-lactam test-dose protocol and antimicrobial stewardship in patients with a history of penicillin allergy

Background

Penicillin allergy is the most commonly reported drug allergy in hospitalized patients, resulting in increased second-line antibiotic use, nosocomial infections, and health care use. Given that most patients are not truly allergic, a safe strategy that empowers the admitting physician is needed.

Differential cytokine induction by doses of lipopolysaccharide and monophosphoryl lipid A that result in equivalent early endotoxin tolerance.

The phenomenon of early endotoxin tolerance, which is induced by sublethal injection of lipopolysaccharide (LPS), results in a protracted period of hyporesponsiveness that is most profound at 3 to 4 days after injection and is marked by reduced cytokine production after a challenge injection of LPS. Early endotoxin tolerance is also induced by the nontoxic LPS derivative monophosphoryl lipid A (MPL), although much more of the monophosphoryl derivative is required to produce a state of tolerance equivalent to that evoked by LPS. In this study, equivalent tolerance-inducing doses of LPS and MPL were tested, and the levels of cytokines induced by LPS and MPL were compared. Although induced levels of colony-stimulating factor were comparable following doses of LPS and MPL that elicited an equivalent state of early endotoxin tolerance, levels of tumor necrosis factor, interleukin-6, and interferon were significantly lower in MPL-injected animals. These results suggest that the lowered toxicity of MPL may be related to its elicitation of significantly lower levels of potentially toxic intermediaries such as tumor necrosis factor, interferon, and interleukin-6.     

Natural History of Mouse Syngeneic Lymphoma: Morphologic and Immunologic Aspects

The morphologic changes in lymphoreticular tissues and development of antitumor immune reactions of specific pathogen-free mice injected with syngeneic lymphoma cells were sequentially analyzed. The regional (right inguinal) lymph node demonstrated mild changes indicative of immunologic response. Systemic lymph nodes revealed a moderate degree of immune response on morphologic basis. The spleen was the site of marked activity, characterized by the presence of large pyroninophilic cells and germinal centers. Foci of necrosis in the local tumor accompanied by mature lymphocytes suggested cell-mediated immune rejection. Mice developed circulating antibodies 2 days after implantation. No antibodies were demonstrated attached to fresh tumor cells. Lymphocyte cytotoxic activity was demonstrated beginning on day 4. Both cytotoxic activity and circulating antibodies were no longer detectable after the third week following tumor implantation. Tumor-bearing mice also had an impaired capacity to mount a primary immune reaction to sheep red blood cells. The spleen demonstrated a marked loss of lymphocytes and the subsequent appearance of masses of amyloid material. It is suggested that amyloidosis in lymphoreticular organs is the result of a derangement in the immune response of the host following a prolonged and sustained antigenic stimulation. It appears that in syngeneic pathogen-free mice the spleen plays the major role in immune rejection mechanisms while the draining node only plays a modest role.     

Association of defensin beta-1 gene polymorphisms with asthma

BACKGROUND: Defensins are antimicrobial peptides that may take part in airway inflammation and hyperresponsiveness. OBJECTIVE: We characterized the genetic diversity in the defensin beta-1 (DEFB1) locus and tested for an association between common genetic variants and asthma diagnosis. METHODS: To identify single nucleotide polymorphisms (SNPs), we resequenced this gene in 23 self-defined European Americans and 24 African Americans. To test whether DEFB1 genetic variants are associated with asthma, we genotyped 4 haplotype-tag SNPs in 517 asthmatic and 519 control samples from the Nurses' Health Study (NHS) and performed a case-control association analysis. To replicate these findings, we evaluated the DEFB1 polymorphisms in a second cohort from the Childhood Asthma Management Program. RESULTS: Within the NHS, single SNP testing suggested an association between asthma diagnosis and a 5' genomic SNP (g.-1816 T>C; P = .025) and intronic SNP (IVS+692 G>A; P = .054). A significant association between haplotype (Adenine, Cytosine, Thymine, Adenine [ACTA]) and asthma ( P = .024) was also identified. Associations between asthma diagnosis and both DEFB1 polymorphisms were observed in Childhood Asthma Management Program, a second cohort: g.-1816 T>C and IVS+692 G>A demonstrated significant transmission distortion ( P = .05 and .007, respectively). Transmission distortion was not observed in male subjects. The rare alleles (-1816C and +692A) were undertransmitted to offspring with asthma, suggesting a protective effect, contrary to the findings in the NHS cohort. Similar effects were evident at the haplotype level: ACTA was undertransmitted ( P = .04) and was more prominent in female subjects ( P = .007). CONCLUSION: Variation in DEFB1 contributes to asthma diagnosis, with apparent gender-specific effects.     

Characterization of the molecular chaperone calnexin in the channel catfish, Ictalurus punctatus, and its association with MHC class II molecules

Folding and assembly of MHC molecules in mammals occurs in the endoplasmic reticulum (ER), but has not been studied in teleosts. Calnexin (CNX) is an ER chaperone that associates with glycoproteins bearing a monoglucosylated N-linked oligosaccharide side chain. Here we report the first identification and characterization of a full-length CNX cDNA clone in a teleost, and the association of the CNX chaperone with MHC class II in a channel catfish T cell line. The 1.8 kb CNX clone encodes a protein of 607 amino acids that is 72% identical to the consensus sequence of mammalian CNXs. The association of CNX with class II is of particular interest because the native MHC class II alpha chain of Ictalurus punctatus does not bear any N-linked oligosaccharide consensus glycosylation sequences. Thus the assembly of class II molecules in the catfish probably proceeds via different steps than occurs in mammals.     

Mutations in the human melanocortin-4 receptor gene associated with severe familial obesity disrupts receptor function through multiple molecular mechanisms

Mutations in the melanocortin-4 receptor gene (MC4R) represent the commonest monogenic cause of human obesity. However, information regarding the precise effects of such mutations on receptor function is very limited. We examined the functional properties of 12 different mutations in human MC4R that result in severe, familial, early-onset obesity. Of the nine missense mutants studied, four were completely unable to generate cAMP in response to ligand and five were partially impaired. Four showed evidence of impaired cell surface expression and six of reduced binding affinity for ligand. One mutation in the C-terminal tail, I316S, showed reduced affinity for alpha-MSH but retained normal affinity for the antagonist AgRP. None of the mutations inhibited signaling through co-transfected wild-type receptors. Thus, in the most comprehensive study to date of the functional properties of naturally occurring MC4R mutations we have (1) established that defective expression on the cell surface is a common mechanism impairing receptor function, (2) identified mutations which specifically affect ligand binding affinity thus aiding the definition of receptor structure-function relationships, (3) provided evidence against the notion that these receptor mutants act as dominant-negatives, and (4) identified a potentially novel molecular mechanism of receptor dysfunction whereby a mutation alters the relative affinities of a receptor for its natural agonist versus antagonist.