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Biomedical subjects

D Lang

Publications and source records attributed to D Lang.

At least 127 records · Page 7Linked to original sources
PubMed1994

Crystallization and preliminary X-ray analysis of a lipase from Chromobacterium viscosum.

Lipase from Chromobacterium viscosum has been purified to homogeneity and crystallized in a form suitable for X-ray diffraction analysis from 10-14% polyethylene glycol 4000 and 10-14% 2-methyl-2,4-pentane diol at pH 6.4 in the presence of 0.25%(w/v) n-octyl-beta-D-glucopyranoside. These crystals belong to space group P2(1)2(1)2 with refined lattice constants a = 41.1 A, b= 156.8, c = 43.6 A, indicating a cell content of one monomer per asymmetric unit of the crystal. The crystals diffract to a resolution of 2.2 A.

Journal Article↗
PubMed1994

Monocyte activation for enhanced tumour necrosis factor-alpha and interleukin 6 production during chronic renal allograft rejection.

To evaluate the contribution of immune mechanisms in the initiation and progression of chronic renal allograft rejection we investigated monocyte-derived cytokine synthesis in vitro in 16 patients with histologically proven chronic rejection; 22 transplant patients with stable function served as controls. Basal tumour necrosis factor-alpha (TNF-alpha) production, measured by L 929 bioassay, was low and not significantly different in both groups. By triggering TNF-alpha formation in vitro by lipopolysaccharide (LPS), high concentrations of TNF-alpha (155.1 +/- 243.0 ng/ml) were measured in monocyte cultures from chronic rejection patients which greatly exceeded the TNF-alpha levels of 11.5 +/- 14.5 ng/ml in the control group. Measurement of interleukin 6 (IL-6) levels by enzyme immunoassay gave similar results, with significantly higher IL-6 concentrations in LPS-triggered monocyte cultures from chronic rejection compared with stable function patients. Additional stimulation of LPS-treated monocytes with interferon-gamma (IFN-gamma) as a priming agent enhanced TNF-alpha formation in stable function patients and, in contrast, slightly reduced monokine formation in chronic rejection patients, which suggests that in this group a high activation level of monocytes has already been reached in vivo by T cell factors such as IFN-gamma. Treatment of monocyte cultures in vitro with prednisolone reduced TNF-alpha formation differently in most but not all cultures from chronic rejection and stable function patients; thus this in vitro test system might be helpful in predicting the benefit of an intensified immunosuppressive regimen for chronic rejection patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Identification of binding sites for the 86-kilodalton IE2 protein of human cytomegalovirus within an IE2-responsive viral early promoter.

The 86-kDa IE2 protein (IE86) of human cytomegalovirus (HCMV) can act as both an activator and a repressor of gene expression. The mechanisms for both of these functions are not well defined. It has recently been demonstrated that this protein has sequence-specific DNA binding properties: it interacts directly with a target sequence that is located between the TATA box and the cap site of its own promoter. This sequence, termed the CRS (cis repression signal) element, is required for negative autoregulation of the IE1/IE2 enhancer/promoter by IE2. We demonstrate now that binding of this protein to DNA is not confined to this site but occurs also within an early promoter of HCMV that has previously been shown to be strongly IE2 responsive. By DNase I protection analysis using a purified, procaryotically expressed IE2 protein, we could identify three binding sites within the region of -290 to -120 of the UL112 promoter of HCMV. Competition in DNase I protection experiments as well as gel retardation experiments showed that the identified binding sites are specific and have high affinity. Deletion of IE2 binding sites from this promoter reduced the level of transactivation; however, the remaining promoter could still be stimulated about 40-fold. Constructs in which IE2 binding sites were fused directly to the TATA box of the UL112 promoter did not reveal a significant contribution of these sequences to transactivation. However, if an IE2 binding site was reinserted upstream of nucleotide -117 of the UL112 promoter, an increase in transactivation by IE2 was obvious, whereas a mutated sequence could not mediate this effect. This finding suggests that DNA-bound IE2 can contribute to transactivation but seems to require the presence of additional transcription factors. Moreover, a comparison of the detected IE2 binding sites could not detect a strong homology, suggesting that this protein may be able to interact with a broad spectrum of different target sequences.

Base Sequence↗
PubMed1994

Post-traumatic amnesia: still a valuable yardstick.

Records of coma and post-traumatic amnesia (PTA) were collected for a group of 38 patients with closed head injury. The results confirmed earlier studies indicating that patients may have short or negligible coma but report prolonged PTA. Comparison of eight patients with prolonged PTA (> 7 days) and short coma (< 6 hours) with the rest of the group on MRI in the acute stage showed that these patients had significantly more extensive hemispheric damage. In the group as a whole both coma and PTA were related to the number of areas in central brain structures in which lesions were detected, but only PTA was significantly related to the number of hemispheric areas in which lesions were found. It is concluded that although both coma and PTA are related to brain damage they reflect disparate patterns of lesions. Assessment of PTA can thus provide additional information concerning severity of injury.

Adolescent↗
PubMed1994

Differential effects of insulin-like growth factor I and platelet-derived growth factor on growth response, matrix formation, and cytosolic free calcium of glomerular mesangial cells of spontaneously hypertensive and normotensive rats.

In this study, we compared the cellular functions of cultured glomerular mesangial cells (MC) from spontaneously hypertensive rats (SHR) and from normotensive Wistar-Kyoto rats (WKY) in response to the growth factors insulin-like growth factor I (IGF-I) and platelet-derived growth factor (PDGF). IGF-I and PDGF at a concentration above 2 ng/ml and a combination of both tested growth factors exerted a highly elevated growth response of SHR MC versus WKY MC. The total RNA synthesis induced by IGF-I and PDGF was increased in SHR MC as compared with WKY MC, while the overall protein synthesis showed no differences between both strains. Analysis of cell-associated fibronectin accumulation and incorporation of proline into collagenous proteins revealed an enhanced basal and PDGF-stimulated matrix formation of SHR MC which was not dependent on the increased production of autocrine matrix-stimulatory mediators by SHR MC. Changes of cytosolic free calcium - [Ca2+]i - could not be correlated with the enhanced responsiveness of SHR MC to the tested growth factors. The described differences of cellular functions between SHR and WKY MC may contribute to pronounced glomerular alterations such as glomerulosclerosis seen in primary and secondary forms of hypertension.

Animals↗
PubMed1994

[Sinus node dysfunction in children without heart defect].

Sinus node dysfunction (SND) is a rare cause of bradycardia in children without structural heart disease. The clinical and diagnostic findings in 4 children with this condition are described. Two of them presented with symptoms, in one arrhythmias had been noted before birth, and a routine physical examination had revealed bradycardia in another. Age at onset of either clinical symptoms or bradycardia ranged from 0 to 11 1/2 years. Routine and 24-h-electrocardiograms showed atrioventricular junctional rhythms with minimal rates of 25/min and episodes of asystole with a maximal duration of 10.3 s. Other electrocardiographic abnormalities such as first degree atrioventricular block, ventricular extrasystoles or tachycardia were common findings. Electrophysiological studies were performed in 3 cases and confirmed the diagnosis of SND. A permanent pacemaker was inserted in 2 children; medical treatment did not have any long-term effect. During a follow-up period of 5 to 13 years there were no complications. In summary, SND in childhood can be assessed by Holter monitoring with high reliability. Electrophysiological studies are not necessary and of limited value. Therapeutic policies and prognostic statements are difficult to establish due to the small number of cases so far described. Permanent cardiac pacing, however, is unavoidable in symptomatic children.

Bradycardia↗
PubMed1994

Development of infant botulism in a 3-year-old female with neuroblastoma following autologous bone marrow transplantation: potential use of human botulism immune globulin.

Infant botulism is a rare disease caused by the release of toxin produced in the intestinal tract by Clostridium botulinum. The disease primarily affects infants under 1 year of age. We report a 3-year-old child with stage IV neuroblastoma who developed symptoms of progressive motor weakness, bulbar palsy and respiratory failure 42 days after autologous BMT. The diagnosis of infant botulism was established by identifying botulism toxin in the stool. Human botulism immune globulin (HBIG) was administered. Following the diagnosis, the patient made significant recovery over the next 7 weeks and was successfully extubated from mechanical ventilation. However, her neuroblastoma eventually recurred and she subsequently died of progressive disease. Although the etiology of the development of infant botulism in this case following autologous BMT still remains unclear, alteration of the intestinal microbial environment from gut sterilization and laminar airflow room isolation or, alternatively, immune suppression during pre- and post-autologous BMT and activation of endogenous spores may have contributed to the development of this disease. The use of HBIG in children with botulism over 1 year of age may be beneficial.

Bone Marrow Transplantation↗
PubMed1993

Plasma L-arginine levels in a rabbit model of hypercholesterolaemia.

A novel method for the quantitation of L-arginine in plasma samples has been developed, based on the technique of enantiomer labelling coupled to the capillary gas chromatographic separation of amino acids. Using this technique plasma L-arginine levels have been measured in rabbits fed a 1% cholesterol-containing diet and compared with rabbits fed a standard diet. Blood cholesterol levels were significantly elevated in the rabbits fed cholesterol but no significant difference was found in plasma L-arginine levels between the cholesterol-fed and control animals. No D-arginine was found in any of the plasma samples. It is concluded that the impairment in endothelium-dependent relaxation previously described in this animal model of hypercholesterolaemia is not due to deficiency of plasma L-arginine.

Animals↗
PubMed1993

Platelet-activating factor antagonism attenuates platelet and neutrophil activation and reduces myocardial injury during coronary reperfusion.

Platelet-activating factor (PAF) is known to be synthesized during tissue reperfusion and to be involved in the activation of platelets and neutrophils in inflammatory processes. The hypothesis of the present study is that PAF is central in the pathophysiology of myocardial reperfusion and that specific PAF receptor antagonism may reduce myocardial reperfusion injury. Utilizing an intact sheep model that involved a 90-min occlusion of the mid-left anterior descending coronary artery followed by 6 hr of reperfusion, a study group that received a specific PAF receptor antagonist (L-659,989, 5 mg/kg) 10 min before reperfusion was compared to a control group that received a saline placebo (n = 8 in each group). Coronary sinus platelet aggregating activity and neutrophil oxidative burst were studied by standard platelet aggregometry and the 2',7'-dichlorofluorescein flow cytometric assay, respectively. Left coronary flow and left ventricular functions measured as peak +/- dp/dt and stroke work were analyzed. The extent of myocardial infarction at the end of 6 hr of reperfusion was measured by standard histochemical stainings. The results demonstrated that platelets were hyperaggregable and that neutrophil oxidative burst was increased in the myocardial compartment during the first 3 hr of coronary reperfusion after 90 min of ischemia. The administration of the PAF antagonist immediately before reflow effectively prevented the activation of platelets and neutrophils. This was associated with significantly improved coronary reflow and ventricular function during the observed reperfusion period and with reduced myocardial infarct measured at 6 hr of reperfusion. We conclude that the use of a specific PAF receptor antagonist, L-659,989, immediately before controlled coronary reflow attenuated the activation of platelets and neutrophils that occurred during reperfusion. These anti-platelet and anti-neutrophil effects together with the inhibition of the known direct deleterious effects of PAF on the myocardium translated into improved ventricular function and reduced myocardial infarct.

Adenosine Diphosphate↗
PubMed1993

A prospective study of blood loss with excisional therapy in pediatric burn patients.

Major blood loss occurs with excisional therapy of burns. To our knowledge no studies have quantitated blood loss in pediatric patients. This prospective study was performed to analyze blood loss in a pediatric burn population undergoing excision and grafting. Forty-four patients underwent 50 two-stage procedures. Blood loss was determined based on calculations of red cells administered in conjunction with estimates of total circulating red cell numbers. Results showed a mean value (+/- SEM) of 2.8% +/- 0.23% of circulating volume lost as a percentage of total body surface area (TBSA) excised, whereas 1.8% +/- 0.18% of circulating volume was lost as a percentage of TBSA grafted. Assessment of losses by age and depth of wound, patient age, and anatomic site showed no differences between these groups. Tourniquets lowered intraoperative losses but had no effect on overall losses. The value of knowing blood losses precisely is evaluated in terms of efficiency of ordering blood.

Adolescent↗
PubMed1993

The use of MRI in the diagnosis of benign and malignant bone and soft tissue tumours.

Two hundred and thirty four suspected primary bone and soft tissue tumours were investigated using plain films and MRI. The MR appearance of 200 of these tumours was assessed with respect to the intensity of the lesion, the homogeneity of the tumour, the presence or absence of a capsule or lobulation, whether the tumour was whorled or not and whether it contained either fluid or blood. Apart from benign lipomas and some malignant myxoid liposarcomas, however, it seemed virtually impossible to tell one tumour from another and in many cases to differentiate a benign lesion from a malignant tumour using MRI alone. We recommend that the workup of a suspected soft tissue tumour should be initially by MR scanning and that the workup of a suspected malignant bone tumour should be plain films followed by an MRI scan.

Adult↗
PubMed1993

Induction of a calcium-independent NO synthase by hypercholesterolaemia in the rabbit.

Endothelium-dependent and -independent relaxation of aortic ring preparations was assessed and nitric oxide (NO) synthase activity measured in the lung, and cerebellum of cholesterol-fed and normal rabbits. Endothelium-dependent relaxation of acetylcholine and ATP was depressed while that to the calcium ionophore, A23187, was unaltered in the cholesterol-fed group. Relaxation to sodium nitroprusside was however greater in aortae from the cholesterol-fed animals. Neither Ca(2+)-dependent nor Ca(2+)-independent NO synthase activity could be detected in aortae or hearts taken from either group of animals. Activity of both enzymes was unaltered in cerebellae from both groups of animals. Activity of the Ca(2+)-independent enzyme was however significantly greater (ca. 2 fold) in lungs from the cholesterol-fed rabbits though the activity of the Ca(2+)-dependent NO synthase was not significantly altered. This finding may account for the increased production of nitrogen oxides previously observed in this model of hypercholesterolaemia.

Amino Acid Oxidoreductases↗
PubMed1993

The 86-kilodalton IE-2 protein of human cytomegalovirus is a sequence-specific DNA-binding protein that interacts directly with the negative autoregulatory response element located near the cap site of the IE-1/2 enhancer-promoter.

The 86-kDa IE-2 protein of human cytomegalovirus is able to autoregulate its own expression via a short nucleotide sequence, termed the cis repression signal (CRS), that is located between the TATA box and the cap site of the IE-1/2 enhancer-promoter. Here we report that the 86-kDa IE-2 protein can interact directly with the CRS, thus demonstrating that IE-2 is a DNA-binding protein. This could be shown by both DNase I protection and gel retardation experiments using a procaryotically expressed IE-2 protein that was purified to near homogeneity. The interaction was sequence specific since a mutated form of the CRS that had previously been reported to be defective in mediating negative regulation could no longer compete for binding in DNase I protection experiments. In addition, an IE-2-reactive monoclonal antibody was able to elicit a supershift in gel retardation experiments, thus proving the presence of IE-2 within the protein-DNA complex. These results suggest that formation of a specific complex between an IE protein and a target sequence located near the cap site of its own gene promoter may be a common mechanism used by both alphaherpesviruses and betaherpesviruses to autoregulate IE gene transcription, although the sequence requirements differ between the two herpesviral subgroups.

Amino Acid Sequence↗
PubMed1993

Heat stressing stimulates nuclear protein kinase C raising diacylglycerol levels. Nuclear protein kinase C activation precedes Hsp70 mRNA expression.

Protein kinase C (pKC) activity has been studied in rat liver after subjecting animals to heat shocking. Nuclear pKC activity was stimulated owing to heat shocking without any change in the cytosolic enzyme activity. The nuclear diacylglycerol levels were raised owing to heat stress along with the stimulation of polarhead phospholipid hydrolysis. Kinetically, the Vmax of nuclear pKC was enhanced as a result of heat shocking, with no change in apparent Km and with concomitant phosphorylation of nuclear lamin B2. Western blot analysis as well as phorbol dibutyrate binding indicate that pKC protein levels did not change because of heat shocking. The stimulation of nuclear pKC under heat stress conditions represents an in vivo phenomenon and the enzymes stimulation precedes Hsp70 mRNA expression.

Animals↗
PubMed1993

The effects of amrinone versus dobutamine on myocardial mechanics and energetics after hypothermic global ischemia.

The effects on the postischemic myocardium of amrinone and dobutamine were studied in canine hearts that underwent 90 minutes of hypothermic (10 degrees C) arrested ischemia. In an isolated heart preparation cross-circulated by a support dog, left ventricular pressure-volume loops were collected under a constant afterload based on a mock circulatory system and a range of preload conditions controlled by a computerized servo volume pump. Dobutamine (0, 5, 10, 15 micrograms/kg per minute) and amrinone (0, 0.75, 1.5, 3.0 mg/kg) were tested in this order based on the weights of the support dogs in eight experiments. Changes in intrinsic myocardial contractility were analyzed as percent increases in the preload recruitable stroke work area from baselines. Dobutamine exhibited significant dose-related increases in the preload recruitable stroke work area. Amrinone did not produce significant increases in preload recruitable stroke work area at 0.75 mg/kg; amrinone's inotropic effect was equivalent to dobutamine, 5 micrograms/kg per minute at 1.5 mg/kg, and at the maximum dose (3.0 mg/kg) it was equivalent to dobutamine, 10 micrograms/kg per minute. The myocardial energetic efficiency was determined from the analysis of the myocardial oxygen consumption-pressure volume area relationship. The y intercept represents the basal metabolic oxygen requirement of the unloaded beating heart, and the slope is inversely proportional to the rate of energy conversion for increasing loading conditions. Dobutamine significantly increased the y intercepts, but it had no effects on the slopes. These changes demonstrate reduced myocardial efficiencies that are consistent with previous reports. Amrinone (0.75 and 1.50 mg/kg) did not result in change of the y intercepts and the slopes of myocardial oxygen consumption-pressure-volume area relationship from baseline conditions. The y intercept was increased with amrinone (3.0 mg/kg), although still not significantly higher than baseline and not to the extents of the dobutamine group. Dobutamine did not have any primary effect on coronary resistance, while amrinone significantly reduced coronary resistance in all loading conditions at 1.5 and 3.0 mg/kg. This study demonstrates that the inotropic effects of amrinone tested under this constant afterload preparation were lower than those of dobutamine. Amrinone has a superior profile of myocardial efficiency on the postischemic myocardium since it does not produce the oxygen-wasting effects of the traditional inotropic agents such as the beta agonists. This benefit, together with amrinone's coronary dilating effects, critically improves the supply/demand ratio that may be of importance in certain clinical situations.

Amrinone↗
PubMed1992

Analysis of proteins binding to the proximal promoter region of the human cytomegalovirus IE-1/2 enhancer/promoter reveals both consensus and aberrant recognition sequences for transcription factors Sp1 and CREB.

Expression of the immediate early 1 and 2 gene (IE-1/2) of human cytomegalovirus, an important pathogen in immunosuppressed patients, is controlled by a strong enhancer/promoter. To define the promoter domain within this large cis-active region of about 550 nucleotides, DNA-protein interactions were studied. DNase I footprinting experiments using procaryotically expressed transcription factor Sp1 revealed an extensive interaction of this transcription factor with both consensus and aberrant recognition elements within the IE-1/2 promoter region. Protection of these Sp1 binding sites could also be observed when nuclear extracts prepared from HeLa cells and permissive human fibroblast cells were used. After in vitro mutagenesis of Sp1 targets and transient expression of mutagenized CAT-expression plasmids, however, no significant reduction in CAT activities was found. By analyzing a series of 5' deletion mutants of the IE-1/2 promoter region, a strong cis-acting element was localized between nucleotides -94 and -78, upstream of sites that interact with Sp1. Gel retardation experiments demonstrated binding of recombinant transcription factor CREB to this motif which reveals it as an aberrant CREB recognition sequence. Thus, this study identifies several previously unknown binding sites for transcription factors Sp1 and CREB within the proximal promoter region of the IE-1/2 gene, which differ markedly in their relevance for constitutive promoter function.

Antigens, Viral↗
PubMed1992

The effects of flosequinan on endothelin-1-induced changes in inositol 1,4,5-trisphosphate levels and protein kinase C activity in rat aorta.

In rat aorta endothelin-1 (10(-8) M) induces significant increases in inositol 1,4,5-trisphosphate (IP3) levels after a 30 s exposure. An increase in particulate protein kinase C activity is also observed at 30 s with a second peak of activity occurring after 10 min. Flosequinan, at concentrations of 10(-6) M or greater, inhibits these endothelin-1-induced changes in both IP3 and particulate protein kinase C activity in the absence of changes in either cyclic GMP or cyclic AMP. It is likely therefore that flosequinan inhibits the transduction mechanisms between the endothelin-1 receptor and hydrolysis of phosphatidylinositol 4,5-bisphosphate, possibly at the level of a G-protein. These results provide a mechanism to explain the vasodilator effects of flosequinan observed in vitro.

Animals↗