IFNγ and Perforin Cooperate to Control Infection and Prevent Fatal Pathology During Persistent Gammaherpesvirus Infection in Mice

Infection with murine gammaherpesvirus 68 has become an accepted model for studying the virus/host interactions with regard to gammaherpesvirus infections. Previous studies using gene‐deficient mice have revealed that neither IFNγ nor perforin is essential in controlling the outcome of infection or the virus load during chronic infection in C57BL/6 mice. However, pronounced multiorgan fibrosis and splenic atrophy are observed in mice lacking IFNγ or the IFNγ receptor. To study the interplay between perforin and IFNγ in controlling the virus‐induced pathology and the viral load during chronic gammaherpesvirus infection, we infected IFNγ/perforin double‐deficient C57BL/6 mice and followed the course of infection. While absence of perforin prevented the splenic atrophy in IFNγ‐deficient mice, fibrosis did not disappear. Moreover, double‐deficient mice developed extreme splenomegaly, were unable to control the viral load and displayed chronic immune activation. Thus, IFNγ and perforin act in concert to minimize pathology and control the viral load in mice chronically infected with MHV68. Furthermore, while certain aspect of the virus‐induced pathology in IFNγ‐deficient mice may be alleviated in double‐deficient mice, other aspects are exaggerated, and the normal architecture of the spleen is completely destroyed. We believe that these findings add to the understanding of the virus/host interaction during chronic gammaherpes virus infection.     

Eradication of biofilms on tympanostomy tubes with acetic acid treatment: an in vitro study

The purpose was to evaluate the eradicative effect of acetic acid on bacterial biofilm grown on tympanostomy tubes by an in vitro experiment. Biofilms of Pseudomonas aeruginosa and Staphylococcus aureus were grown on sterile tympanostomy tubes for 24 h. The tubes were treated with acetic acid solutions at various concentrations for 24 h. Main outcome was viability of bacteria after treatment. The presence of consistently attached biofilm was examined on selected tympanostomy tubes with confocal laser scanning microscopy. Both pH-adjusted and non-pH-adjusted media solutions were applied as control groups. Results showed complete eradication of P. aeruginosa biofilm with 0.50% v/v acetic acid. Biofilm of S. aureus was eradicated with 1.25% v/v acetic acid. Low pH value alone led to decreased growth of already established biofilm, but not eradication. In conlusion, acetic acid showed an eradicating effect on biofilm established on sterile tympanostomy tubes in vitro.     

Increased levels of circulating free insulin-like growth factors in patients with non-islet cell tumour hypoglycaemia

Summary Non-islet cell tumour hypoglycaemia (NICTH) is characterised by severe and recurrent fasting hypoglycaemia, and is usually caused by secretion of insulin-like growth factor-II (IGF-II) by the tumour. This induces secondary changes in the circulating levels of insulin, growth hormone (GH), and the IGF-binding proteins (IGFBPs), resulting in an increased insulin-like hypoglycaemic activity of IGF-II. A participating role of IGF-I is not established. We measured serum levels of free IGF-I and free IGF-II, total IGF-I, total IGF-II, big IGF-II and IGFBP-1, IGFBP-2 and IGFBP-3 in patients with NICTH before (n = 14) and after surgical removal of the tumour (n = 3). A control group (n = 20) was included for comparison. In NICTH patients, free IGF-II was 20-fold increased (26.8 ± 8.1 [mean ± SEM] vs. 1.3 ± 0.1 μg/l), and free IGF-I was four fold increased (2.8 ± 0.4 vs. 0.7 ± 0.1 μg/l), as compared to control subjects (p < 0.0001). In accordance with earlier observations levels of total IGF-I, total IGF-II, and IGFBP-3 were decreased, whereas IGFBP-1 and IGFBP-2 were increased in NICTH (all p-values < 0.05). The highly elevated levels of free IGF-I and free IGF-II most likely imply a considerable hypoglycaemic insulin-like activity, and may, by negative feedback explain the marked suppression of the GH/IGF-I axis observed in NICTH. Finally, free IGF-II seems to be a powerful biochemical marker in the diagnosis of NICTH. [Diabetologia (1998) 41: 589–594] Received: 21 October 1997 and in final revised form: 15 December 1997     

Early implant‐associated osteomyelitis results in a peri‐implanted bacterial reservoir

Implant‐associated osteomyelitis (IAO) is a common complication in orthopedic surgery. The aim of this study was to elucidate how deep IAO can go into the peri‐implanted bone tissue within a week. The study was performed in a porcine model of IAO. A small steel implant and either 10⁴ CFU/kg body weight of Staphylococcus aureus or saline was inserted into the right tibial bone of 12 pigs. The animals were consecutively killed on day 2, 4 and 6 following implantation. Bone tissue around the implant was histologically evaluated. Identification of S. aureus was performed immunohistochemically on tissue section and with scanning electron microscopy and peptide nucleic acid in situ hybridization on implants. The distance of the peri‐implanted pathological bone area (PIBA), measured perpendicular to the implant, was significantly larger in infected animals compared to controls (p = 0.0014). The largest differences were seen after 4 and 6 days of inoculation, where PIBA measurements of up to 6 mm were observed. Positive S. aureus bacteria were identified on implants and from 25 μm to 6 mm into PIBA. This is important knowledge for optimizing outcomes of surgical debridement in osteomyelitis.     

Placental growth hormone during pregnancy in a growth hormone deficient woman with type 1 diabetes compared to a matching diabetic control group.

In pregnancy, pituitary growth hormone (GH) is gradually replaced by placental growth hormone (hPGH). GH deficient pregnant women may take advantage of GH substitution during pregnancy, but this issue still remains unresolved. Also, in pregnancy diabetes may cause macrosomia. The combination of GH deficiency, GH substitution therapy and type 1 diabetes mellitus may influence pregnancy in unforeseen ways. We present a case of pregnancy in a GH deficient woman with type 1 diabetes who continued on GH replacement until week 21. In gestational week 37 a thin and mildly small-for gestational-age (length 55 cm, +3 SD, 99th centile and weight 2445 g., -1.4 SD, 10th centile) but otherwise healthy boy was born. The patient had levels of serum hPGH at the lower end of the range of values found in a matching group of diabetic women. Serum IGF-I levels were at the upper end of the range of values in the control group. A positive correlation between serum hPGH and IGF-I values was seen in the control group when using the area-under-the-curve (r=0.84; p<0.001). The patient's child had lower birth weight and ponderal index, but was otherwise healthy. Serum IGF-I, but not hPGH, correlated to the absolute birth weight (r=0.63; p=0.015) and the birth weight z-score (r=0.55; p=0.039) in the control group. Serum hPGH and IGF-I declined rapidly after delivery. In conclusion, hPGH correlated to IGF-I in type 1 diabetes mellitus (DM), and IGF-I values correlated to the birth weight. Both type 1 diabetes mellitus and GH deficiency (with GH substitution therapy) may influence fetal growth, and in combination, the net influence may be difficult to predict.     

Aspects of glucose homeostasis in uremia as assessed by the hyperinsulinemic euglycemic clamp technique

A three-step hyperinsulinemic euglycemic clamp was performed in 14 nondialyzed uremic and ten age-matched healthy subjects. Nine of the uremics were restudied for a mean of 42 days (range, 21 to 88 days) after initiation of dialysis therapy. Insulin was infused at the following three rates: 0.5 mU·kg^?1·min^?1, 2.0 mU·kg^?1·min^?1, and 4.0 mU·kg^?1·min^?1. Each dose was given for 120 minutes. Glucose uptake during the last 30 minutes of each clamp were consistently lower in uremic patients pre-dialysis than in controls (2.3 ± 0.3 v 6.6 ± 0.8 mg·kg^?1·min, 7.8 ± 0.6 v 13.2 ± 1.1mg·kg^?1·min^?1 and 9.6 ± 0.7 v 15.5 ± 1.0 mg·kg^?1·min^?1, all P < 0.001). Serum insulin levels wre similar in the two groups, and blood glucose values during steady state were maintained at 79 ± 2, 77 ± 2, and $\text{77 ± 2 mg}\text{100 mL}$ in uremic subjects and at 72 ± 3, 73 ± 2, and $\text{75 ± 2 mg}\text{100 mL}$ in healthy subjects. The insulin levels required to elicit half-maximal biological response in uremics (82 ± 5 μU/mL) were markedly higher than in controls (54 ± 8 μU/mL, P < 0.01). Dialysis therapy enhanced maximal glucose disposal (8.7 ± 0.9 v 11.4 ± 0.8 mg·kg^?1·min^?1, P < 0.01), while insulin concentrations required to achieve half-maximal glucose metabolism were virtually identical in the two situations (86 ± 7 μU/mL and 85 ± 11 μU/mL). No difference in I¹²⁵ insulin binding to monocytes was observed in the uremic patients and a separate control group. In contrast to the impaired glucose uptake in uremia the insulin effect on lipolysis and ketogenesis was normal as estimated by measurement of serum NEFA, blood glycerol and 3-hydroxybutyrate. The response of the gluconeogenic precursors, lactate and alanine, was also similar in the uremic and control subjects. The impaired peripheral glucose uptake in nondialysed uremics could not be ascribed to different levels of cortisol, catecholamines, or NEFA, although a possible participation of growth hormone could not be ruled out. In conclusion, severely impaired peripheral glucose uptake is present in nondialysed uremic subjects. Short-term dialysis therapy (hemodialysis or continuous ambulatory peritoneal dialysis; CAPD) tends to abolish this defect. Since an apparently normal first step in insulin action, namely binding to receptors, was found, the uremic insulin resistance is a result of depressed insulin action at postbinding sites. However, it cannot be excluded that a superimposed intrinsic defect glucose transport system eg an impaired insulin-independent glucose uptake may contribute. In contrast to the abnormal glucose uptake, the responses of key intermediary metabolites were normal in uremia indicating normal insulin action on lipolysis, ketogenesis, and gluconeogenesis.     

Preserved incretin effect in type 1 diabetic patients with end-stage nephropathy treated by combined heterotopic pancreas and kidney transplantation

Insulin secretion is stimulated better by oral than by intravenous glucose (incretin effect). The contribution of the autonomic nervous system to the incretin effect after oral glucose in humans is unclear. We therefore examined nine type 1 diabetic (insulin-dependent) patients with end-stage nephropathy, studied after combined heterotopic pancreas and kidney transplantation, and 7 non-diabetic kidney recipients (matched for creatinine clearance and immunosuppressive medication). The release of gastric inhibitory polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) immunoreactivity and B cell secretory responses (IR insulin and C-peptide) to oral (50 g) and isoglycaemic intravenous glucose (identical glycaemic profile) were measured by radioimmunoassay. The difference in B cell responses between the two tests represents the contribution of the enteroinsular axis to the responses after oral glucose (incretin effect). Insulin responses after the oral glucose challenge were similar in the two patient groups despite systemic venous drainage of the pancreas graft in the pancreas-kidney-transplanted group. In both groups GIP and GLP-1 increased after oral but not after intravenous glucose, and B cell secretory responses were significantly smaller (by 55.2 ± 7.7% and 46.5 ± 12.5%, respectively) with isoglycaemic intravenous glucose infusions. The lack of reduction in the incretin effect in pancreas-kidney-transplanted patients, whose functioning pancreas is denervated, indicates a lesser role for the nervous system and a more important contribution of circulating incretin hormones in mediating the enteroinsular axis in man.     

Testosterone and estradiol regulate free insulin-like growth factor I (IGF-I), IGF binding protein 1 (IGFBP-1), and dimeric IGF-I/IGFBP-1 concentrations

The present study tests the clinical postulate that elevated testosterone (Te) and estradiol (E2) concentrations modulate the effects of constant iv infusion of saline vs. recombinant human IGF-I on free IGF-I, IGF binding protein (IGFBP)-1, and dimeric IGF-I/IGFBP-1 concentrations in healthy aging adults. To this end, comparisons were made after administration of placebo (Pl) vs. Te in eight older men (aged 61 +/- 4 yr) and after Pl vs. E2 in eight postmenopausal women (62 +/- 3 yr). In the saline session, E2 lowered and Te increased total IGF-I; E2 specifically elevated IGFBP-1 by 1.5-fold and suppressed free IGF-I by 34%; and E2 increased binary IGF-I/IGFBP-1 by 5-fold more than Te. During IGF-I infusion, the following were found: 1) total and free IGF-I rose 1.4- to 2.0-fold (Pl) and 2.1-2.5-fold (Te) more rapidly in men than women; 2) binary IGF-I/IGFBP-1 increased 3.4-fold more rapidly in men (Te) than women (E2); and 3) end-infusion free IGF-I was 1.6-fold higher in men than women. In summary, E2, compared with Te supplementation, lowers concentrations of total and ultrafiltratably free IGF-I and elevates those of IGFBP-1 and binary IGF-I/IGFBP-1, thus putatively limiting IGF-I bioavailability. If free IGF-I mediates certain biological actions, then exogenous Te and E2 may modulate the tissue effects of total IGF-I concentrations unequally.