Kidney tubule health scores and their associations with incident CKD in women living with HIV

OBJECTIVES

Individual kidney tubule biomarkers are associated with chronic kidney disease (CKD) risk in people living with HIV (PLWH). Whether a combination of kidney biomarkers can be integrated into informative summary scores for PLWH is unknown.

METHODS

We measured eight urine biomarkers of kidney tubule health at two visits over a 3-year period in 647 women living with HIV in the Women's Interagency Health Study. We integrated biomarkers into factor scores using exploratory factor analysis. We evaluated associations between CKD risk factors and factor scores, and used generalized estimating equations to determine associations between factor scores and risk of incident CKD.

RESULTS

Factor analysis identified two unique factor scores: a tubule reabsorption score comprising alpha-1-microglobulin, beta-2-microglobulin and trefoil factor-3; and a tubule injury score comprising interleukin-18 and kidney injury molecule-1. We modelled the two factor scores in combination with urine epidermal growth factor (EGF) and urine albumin. Predominantly HIV-related CKD risk factors were independently associated with worsening tubule reabsorption scores and tubule injury scores. During a median follow-up of 7 years, 9.7% (63/647) developed CKD. In multivariable time-updated models that adjusted for other factor scores and biomarkers simultaneously, higher tubule reabsorption scores [risk ratio (RR) = 1.27, 95% confidence interval (CI): 1.01-1.59 per 1 SD higher time-updated score], higher tubule injury scores (RR = 1.36, 95% CI: 1.05-1.76), lower urine EGF (RR = 0.75, 95% CI: 0.64-0.87), and higher urine albumin (RR = 1.20, 95% CI: 1.02-1.40) were jointly associated with risk of incident CKD.

CONCLUSIONS

We identified two novel and distinct dimensions of kidney tubule health that appear to quantify informative metrics of CKD risk in PLWH.

Pseudomembranous necrotising pharyngitis in a child with Pseudomonas aeruginosa bacteraemia

Pseudomonas aeruginosa is a common infection in immunocompromised patients. However, it can also cause severe infections in otherwise healthy individuals. We describe pseudomonal bacteraemia in a 6-month-old boy with significant obstruction of the nasopharynx by pseudomonal debris, which we termed pseudomembranous nectrotising pharyngitis. To prevent aspiration and suffocation, early recognition and removal of the obstruction by endoscopy is recommended.

An eight-year-old girl with probable Lyme disease in Hong Kong

An eight-year-old girl presented with acute cerebellar syndrome and meningitis. Lumbar puncture showed elevated pressure. Examination of the cerebrospinal fluid showed lymphocytosis, raised protein and decreased glucose. She was initially treated with acyclovir and antituberculosis drugs with partial response. Subsequently, the antibody assay for Borrelia burgdorferi was positive and the antimicrobial regime was changed to ceftriaxone. She made a full recovery with no neurological deficit. A probable diagnosis of Lyme disease was made and the diagnostic approach to Lyme disease is discussed.

Application of artificial neural networks to establish a predictive mortality risk model in children admitted to a paediatric intensive care unit

INTRODUCTION

Paediatric risk of mortality and paediatric index of mortality (PIM) are the commonly-used mortality prediction models (MPM) in children admitted to paediatric intensive care unit (PICU). The current study was undertaken to develop a better MPM using artificial neural network, a domain of artificial intelligence.

METHODS

The purpose of this retrospective case series was to compare an artificial neural network (ANN) model and PIM with the observed mortality in a cohort of patients admitted to a five-bed PICU in a Hong Kong non-teaching general hospital. The patients were under the age of 17 years and admitted to our PICU from April 2001 to December 2004. Data were collected from each patient admitted to our PICU. All data were randomly allocated to either the training or validation set. The data from the training set were used to construct a series of ANN models. The data from the validation set were used to validate the ANN and PIM models. The accuracy of ANN models and PIM was assessed by area under the receiver operator characteristics (ROC) curve and calibration.

RESULTS

All data were randomly allocated to either the training (n=274) or validation set (n=273). Three ANN models were developed using the data from the training set, namely ANN8 (trained with variables required for PIM), ANN9 (trained with variables required for PIM and pre-ICU intubation) and ANN23 (trained with variables required for ANN9 and 14 principal ICU diagnoses). Three ANN models and PIM were used to predict mortality in the validation set. We found that PIM and ANN9 had a high ROC curve (PIM: 0.808, 95 percent confidence interval 0.552 to 1.000, ANN9: 0.957, 95 percent confidence interval 0.915 to 1.000), whereas ANN8 and ANN23 gave a suboptimal area under the ROC curve. ANN8 required only five variables for the calculation of risk, compared with eight for PIM.

CONCLUSION

The current study demonstrated the process of predictive mortality risk model development using ANN. Further multicentre studies are required to produce a representative ANN-based mortality prediction model for use in different PICUs.

Chorioamnionitis with or without funisitis increases the risk of hypotension in very low birthweight infants on the first postnatal day but not later

OBJECTIVE

To evaluate the relation between chorioamnionitis and hypotension in very low birthweight infants.

METHODS

Retrospective cohort study in infants with a birth weight of <1500 g born between January 2002 and September 2004. The placentas were examined for evidence of chorioamnionitis and funisitis. Hypotension was defined by the use of vasopressors.

RESULTS

Of 105 infants, 37 (35%) were chorioamnionitis positive. The onset of hypotension had a skewed distribution: day 1 for 30 episodes and scattered from day 2 to day 19 for the remaining 22. Of the 30 infants who developed hypotension on day 1, 17 (57%) were chorioamnionitis positive. The mean maturity of the chorioamnionitis positive group was 27.91 weeks, marginally less than the mean maturity of 29.05 weeks of the chorioamnionitis negative group (p = 0.05). After adjustment of the effects for confounding variables (birth weight, gestation, surfactant therapy, mechanical ventilation on day 1, high frequency oscillatory ventilation, patent ductus arteriosus), chorioamnionitis was the significant factor in line with hypotension developing on day 1 (adjusted odds ratio 5.14, 95% confidence interval 1.51 to 17.50). There was no evidence that hypotension developing after day 1 was associated with chorioamnionitis.

CONCLUSIONS

There is a strong association between chorioamnionitis and hypotension developing on day 1 in very low birthweight infants.

Obstructive sleep apnoea in children with Down syndrome

INTRODUCTION

Children with Down syndrome (DS) are prone to develop obstructive sleep apnoea (OSA) for a combination of reasons, including small upper airway, midfacial hypoplasia, micrognathia and muscular hypotonia. The objective of this study was to compare the prevalence of OSA in DS children, with or without snoring, with snoring children matched for gender, age and weight for height.

METHODS

DS children were prospectively recruited from the Hong Kong Down Syndrome Association. All recruited DS children underwent a sleep polysomnography (PSG) in our sleep laboratory. The same number of patients without DS who underwent sleep PSG in the same period were enrolled as controls after they were matched for gender, age and weight for height. OSA was defined as apnoea-hypopnoea index (AHI) greater than 1.5.

RESULTS

22 DS patients and 22 snoring controls completed the overnight PSG. The mean age of DS children and snoring controls was 10.82 +/- 5.93 and 10.27 +/- 5.68 years, respectively. The prevalence of OSA was 59 percent in DS children and 32 percent in snoring controls. Median and interquartile range (IQR) of AHI of DS children (median 1.80, IQR is 0.40 to 7.10) were significantly higher than those of controls (median 0.50, IQR is 0.00 to 2.03, p-value equals 0.041). Out of 13 DS children with OSA, eight of them (61.5 percent) had no habitual snoring.

CONCLUSION

59 percent of DS children in the current series were found to have OSA and they were more likely to develop OSA than controls. Nearly 40 percent of DS children with OSA did not have habitual snoring.

Childhood sleep-disordered breathing and its implications for cardiac and vascular diseases

OBJECTIVE

To systematically evaluate the recent literature regarding the relationship between childhood sleep-disordered breathing (SDB)/obstructive sleep apnoea (OSA) and cardiovascular diseases in children.

METHODS

The literature about SDB/OSA and blood pressure, sympathetic activation, arterial distensibility, ventricular hypertrophy and insulin resistance were studied. Meta-analysis of risk of hypertension and high apnoea-hyponoea index were performed to calculate the combined odds ratio and it is equal to 2.93 (95% CI = 1.18-7.29).

RESULTS

The results suggest a significant association between SDB/OSA and hypertension. However, the data are not adequate to draw firm conclusion although evidences were emerging to suggest that SDB/OSA affects blood pressure in either directions in children. Limited evidences also suggest that SDB/OSA is associated with increased sympathetic activation, decreased arterial distensibility and ventricular hypertrophy.

CONCLUSIONS

There is now increasing but not adequate evidence that childhood SDB/OSA is associated with detectable cardiovascular abnormalities.

Bacteriological screening of expressed breast milk revealed a high rate of bacterial contamination in Chinese women

A screening programme for expressed breast milk (EBM) revealed the alarming fact that our study group had the highest rate of contamination ever reported. The programme started in July 2002 and involved a group of Chinese women whose premature babies were in the neonatal intensive care unit. EBM was considered to be contaminated if there was any growth of pathogens, including Gram-negative bacteria, enterococci or Staphylococcus aureus, or if the total bacterial count was >10(5) cfu/mL. Of 59 samples from 23 mothers, 63% were contaminated. This high contamination rate could be due to the Chinese tradition of avoiding bathing for one month after childbirth. Previous studies have shown that feeding EBM rather than premature infant formula milk has advantages in terms of decreased incidence of necrotizing enterocolitis and neonatal sepsis. However, in this population, with such a high incidence of contaminated EBM, this may not be the case. Further studies to compare EBM with premature infant formula in this population are required.

Synthesis, structure, spectroscopic properties, and electrochemistry of rare earth sandwich compounds with mixed 2,3-naphthalocyaninato and octaethylporphyrinato ligands

A series of 14 heteroleptic rare earth sandwich complexes [M(III)-(nc)(oep)] (M=Y, La-Lu except Ce and Pm; nc=2,3-naphthalocyaninate; oep = octaethylporphyrinate) have been prepared by a one-pot procedure from corresponding [M(acac)3] . nH2O (acac = acetylacetonate), metal-free porphyrin H2(oep), and naphthalonitrile the presence of 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) in n-octanol. The molecular structures of four of these complexes (M = Sm, Gd, Y, Lu) are isostructural, exhibiting a slightly distorted square antiprismatic geometry with two domed ligands. The interplanar distance decreases from 2.823 to 2.646 A along the series as a result of lanthanide contraction. The whole series of complexes have also been characterized spectroscopically. All the electronic absorptions, except the two B-bands due to nc and the oep rings, are metal-dependent, indicating that there are substantial pi-pi interactions. The hole or the unpaired electron in these double-deckers is delocalized over both macrocyclic ligands, as evidenced by the co-appearance of the IR marker bands for the nc*- (1315-1325 cm(-1)) and oep*- (1510-1531 cm(-1)) T radical ions. Three one-electron oxidation couples and up to three one-electron reduction couples have been revealed by electrochemical methods. All the potentials are linearly dependent on the size of the metal center. The changes in absorption spectra during the first electro-oxidation and reduction of the La(III), Eu(III), and Y(III) double-deckers have also been studied spectroelectrochemically. The spectral data recorded for [M(III)(nc)(oep)]-(M = Y, La-Lu except Ce and Pm) reduced chemically with hydrazine hydrate are in accord with those obtained by spectroelectrochemical methods. The first heteroleptic naphthalocyaninate-containing triple-deckers [M(III)2(nc)-(oep)2] (M = Nd, Eu) have also been prepared by a raise-by-one-story method by using [M(III)(nc)(oep)] (M = Nd, Eu), [M(acac)3] . nH2O (M = Nd, Eu), and H2(oep) as starting materials. The compounds adopt a symmetrical triple-decker structure with two outer oep rings and one inner nc ring, which has been confirmed by 'H NMR spectroscopy and X-ray structural determination of the Nd complex. Both compounds give a near-IR absorption at 1021 nm (for M=Nd) or 1101 nm (for M = Eu), which has rarely been observed for neutral (or hole-free) triple-decker complexes and can be ascribed to the lowest-energy Q'(0, 0) transition. Similarly to the double-decker analogues. these triple-decker complexes undergo a series of one-electron transfer processes with a relatively small potential gap (1.1 -1.2 V) between the first oxidation and the first reduction.

Nocturnal enuresis and obstructive sleep apnoea in two children

Nocturnal enuresis was a symptom of childhood obstructive sleep apnoea, OSAS. We reported two children with secondary nocturnal enuresis which disappeared after tonsillectomy and adenoidectomy for proven OSAS. Pathogenesis of secondary nocturnal enuresis in OSAS was discussed.

A prospective study of a one-week nonbismuth quadruple therapy for childhood Helicobacter pylori infection

PURPOSE

In the eradication of Helicobacter pylori infection, a 1-week therapy improves patient compliance, but drug resistance may limit its efficacy. The effectiveness of the 1-week nonbismuth quadruple therapy was studied prospectively in children with proven H pylori infection in a population with a high rate of metronidazole resistance.

METHODS

All pediatric patients who presented to our institutions with acute and chronic upper gastrointestinal conditions requiring endoscopy from June 1997 to February 2000 were investigated prospectively for H pylori infection. Gastric biopsy specimens were analyzed with rapid urease test and histopathology, H pylori-positive children were treated with omeprazole, clarithromycin, amoxicillin, and metronidazole for 7 days. The result of treatment was assessed 1 month after treatment with endoscopy and biopsy. The same treatment was repeated for 2 weeks if H pylori was still present. In patients who needed a third endoscopy, their biopsy specimens were cultured to determine antibiotic sensitivity. Results were correlated with patients' symptoms and endoscopic findings.

RESULTS

Thirty-three children with acute (severe epigastric pain, n = 14; gastrointestinal bleeding, n = 9) and chronic (recurrent abdominal pain, n = 7; anemia, n = 3) conditions were treated for H pylori. Thirty-one (94%) were confirmed to have H pylori eradicated by a 1-week therapy, whereas 1 patient had eradication after a further 2-we'ek therapy (3.3%). The only unresponsive patient had H pylori resistant to both clarithromycin and metronidazole. All ulcers and erosions healed after the eradication of H pylori. Three patients had persistent recurrent abdominal pain despite H pylori eradication.

CONCLUSIONS

The 1-week therapy with omeprazole, clarithromycin, amoxicillin, and metronidazole is an effective treatment of H pylori in children in a population with a high incidence of metronidazole resistant strain of H pylori. Peptic ulcers and erosions healed with the eradication of the bacteria.

First fatal case of enterovirus 71 infection in Hong Kong

Enteroviruses are a common cause of childhood infections, from hand, foot and mouth disease, to lethal brainstem encephalitis. Enterovirus 71 was first isolated in 1969. Brainstem encephalomyelitis and pulmonary oedema are postulated to be causally related and have been found to be a common feature of fatal enterovirus 71 cases. A fatal case of enterovirus 71 infection in a 2-year-old, previously healthy boy is reported. He presented to the Department of Paediatrics with clinical features of sepsis within 3 days of onset of fever. A few minutes after injection of midazolam, fentanyl and vecuronium for intubation, cardiac arrest developed and was not amenable to various treatment modalities. Pulmonary haemorrhage and oedema were noted during intubation, and postmortem examination confirmed the presence of brainstem encephalomyelitis.

Tetrapyrrole derivatives substituted with ferrocenylethynyl moieties. synthesis and electrochemical studies

Up to eight redox-active ferrocenyl units have been incorporated, through the unsaturated ethynyl linkers, on the periphery of a series of cyclic tetrapyrrole derivatives including zinc(II) phthalocyanine and 2,3-naphthalocyanine, and nickel(II) meso-diphenylporphyrin. The synthesis of the former two macrocycles 4 and 7 involves the Sonogashira coupling reaction of ferrocenylethyne with 4,5-dichlorophthalonitrile (1) or 6,7-dibromonaphthalonitrile (5), respectively, followed by a base-promoted cyclization. The meso-bis(ferrocenylethynyl)porphyrin 11 has been prepared from the dibromo analogue 10 also by a palladium-catalyzed coupling reaction. These novel macrocyclic compounds have been spectroscopically and electrochemically characterized. As revealed by cyclic voltammetry, the ferrocenyl moieties appear to be electrochemically independent in these complexes and there is no significant electronic coupling among the iron(II) centers.

Pulmonary sequelae in long-term survivors of bronchopulmonary dysplasia

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a common problem in premature babies. Long-term sequelae are the main concerns.

METHODS

A retrospective review of all BPD children born in Queen Mary Hospital, a teaching hospital of the University of Hong Kong, from January 1987 to December 1995 was conducted. Children with cerebral palsy, immunodeficiency, congenital heart disorders, renal or liver failure were excluded from analysis. Chest radiography (CXR), electrocardiogram (ECG) and pulse oximetry were routinely performed.

RESULTS

Fifty-five children completed the study. The female to male ratio was 1:1.1. The mean gestational age was 28 weeks. Twenty-five children were born with a birthweight of less than 1001 g. Mean age at assessment was 5.4 years. Twenty-four children (44%) demonstrated signs or symptoms of current asthma. Only seven children managed to perform the spirometry satisfactorily. One child had low forced vital capacity and one had hyperresponsive airway. The only risk factor found to be associated with current asthma was the birth month, with those children born early in the year at higher risk of developing current asthma. Seventeen of 48 children (35%) had a bodyweight below the third percentile at the corrected age of 1 year. Eleven of these seventeen children (65%) demonstrated catch-up growth at assessment. Abnormal CXR was found in 25 of 40 children (63%). All had normal pulse oximetry and ECG.

CONCLUSIONS

Bronchopulmonary dysplasia children had a significantly higher risk than the general population of developing current asthma (odds ratio 4.7; 95% confidence interval 3.4-6.5; P<0.0001). The importance of birth month suggests that early life experience is important in the pathogenesis of asthma, even in BPD children. The long-term growth of BPD children was much better than previously reported.

Use of montelukast in the treatment of early childhood wheezing from clinical experience with three cases

Leukotrienes were found to be raised in respiratory syncytial virus bronchiolitis. Montelukast is a cysteinyl leukotrienes antagonist. We report our experience with the use of montelukast in three young children from 5-months to 20-months old. The first case was a 5-month-old boy with previous good health. He had prolonged respiratory distress secondary to adenovirus type 3 infection. The second case was a 20-month-old boy with bronchopulmonary dysplasia. He had respiratory syncytial virus and an adenovirus type 3 infection leading to prolonged wheeze. The third case was a 20-month-old girl with chronic lung disorder after an episode of severe E. coli pneumonia at 1 month old. She developed acute virus-negative severe wheeze after a few days of running nose and low-grade fever. All three cases responded poorly to inhaled steroids and bronchodilators. Addition of montelukast was associated with marked clinical improvement within 1 week. The three cases were very heterogeneous and differed from usual simple virus-induced acute bronchiolitis. The use of multiple drugs including montelukast did not enable any definite conclusions; however, the addition of montelukast was closely related to clinical improvement. Further studies in the use of montelukast in severe virus-induced bronchiolitis are warranted.

Unilateral right-sided internal jugular phlebectasia in asthmatic children

The most common cause of a neck mass that increases in size on straining is laryngocele. Internal jugular phlebectasia, which is of unknown cause, may present similarly. We present three cases of internal jugular phlebectasia, all of whom were asthmatic children. This association of asthma and internal jugular phlebectasia has not been reported previously.

A randomized controlled trial of azithromycin and amoxycillin/clavulanate in the management of subacute childhood rhinosinusitis

OBJECTIVE

Subacute childhood rhinosinusitis is a disorder commonly seen in children with allergic rhinitis. Antibiotics have been recommended as a major component of the treatment regime. The objective of the present study was to compare the effectiveness of a 3-day course of azithromycin and a 2-week course of amoxycillin/clavulanate in the treatment of subacute childhood rhinosinusitis.

METHODOLOGY

A randomized single-blinded control study of subacute rhinosinusitis was conducted, comparing a 3-day course of azithromycin and a 2-week course of amoxycillin/clavulanate. Inclusion criteria were children aged between 5 and 16 years, duration of nasal blockage or discharge between 30 and 120 days, and abnormal sinus radiographs. All enrolled children were prescribed budesonide nasal spray (Rhinocort Aqua Nasal Spray, Astra Pharmaceuticals, Sodertalje, Sweden) as adjuvant treatment.

RESULTS

Forty-two children were recruited into the study and one defaulted on follow-up. Failure occurred in 6 of 20 for the azithromycin group and 5 of 21 for the amoxycillin/clavulanate group. The odds ratio was 1.46 (95%CI 0.37-5. 80, P = 0.73). No relapse occurred in azithromycin group and 5 of 21 in amoxycillin/clavulanate group. The odds ratio was 0.16 (95%CI 0. 017-1.51, P = 0.18). Both antibiotics were well tolerated, however, two children, one from each group, complained of mild transient epigastric discomfort.

CONCLUSIONS

This small study did not provide evidence of a difference between 14 days of amoxycillin/clavulanate and 3 days of azithromycin. Larger studies will be needed to determine which, if any, antibiotic regimen should be used in treating subacute childhood rhinosinusitis.

Use of infrared emission detection thermometer in Chinese neonates

OBJECTIVE

To evaluate the reproducibility of Thermoscan, an infrared emission detection ear thermometer, and to establish the normal reference range of ear temperature in Chinese neonates.

METHODS

Neonates were recruited from the inpatients population with exclusion of those suffering from infections.

RESULTS

Forty-nine neonates were recruited with 1,115 temperature taking sessions. Mean left ear temperature was 36.64 degrees C +/- 0.35 degree C. Mean right ear temperature was 36.64 degrees C +/- 0.37 degree C. Clinical repeatability for left and right ear was 0.17 degree C and 0.17 degree C, respectively.

CONCLUSION

Thermoscan produced reproducible results in Chinese neonates. The normal range of ear temperature for Chinese neonates is 35 degrees C to 37 degrees C. Ear temperature > 37.8 degrees C should be regarded as fever.

Neonatal Marfan syndrome: a case report

A case of neonatal Marfan syndrome is presented. The patient was noted to have cardiomegaly and tricuspid regurgitation on antenatal ultrasound scan. She was born with long, slender fingers and toes, an aged appearance and non-paralytic hypotonia. Echocardiogram revealed a dilated right atrium, right ventricle, dysplastic tricuspid valve and severe tricuspid regurgitation. She subsequently died of severe heart failure. Post-mortem examination showed the pathological features of lobar emphysema and cystic medial necrosis of the aorta. These features supported the diagnosis of neonatal Marfan syndrome. Nucleotide sequencing showed substitution of G by A at codon 1032 in exon 25 located in the long arm of chromosome 15. This resulted in the substitution of a cysteine by a tyrosine. A de novo mutation is suggested by the absence of affected family members.

Characterization of Urtica dioica agglutinin isolectins and the encoding gene family

Urtica dioica agglutinin (UDA) has previously been found in roots and rhizomes of stinging nettles as a mixture of UDA-isolectins. Protein and cDNA sequencing have shown that mature UDA is composed of two hevein domains and is processed from a precursor protein. The precursor contains a signal peptide, two in-tandem hevein domains, a hinge region and a carboxyl-terminal chitinase domain. Genomic fragments encoding precursors for UDA-isolectins have been amplified by five independent polymerase chain reactions on genomic DNA from stinging nettle ecotype Weerselo. One amplified gene was completely sequenced. As compared to the published cDNA sequence, the genomic sequence contains, besides two basepair substitutions, two introns located at the same positions as in other plant chitinases. By partial sequence analysis of 40 amplified genes, 16 different genes were identified which encode seven putative UDA-isolectins. The deduced amino acid sequences share 78.9-98.9% identity. In extracts of roots and rhizomes of stinging nettle ecotype Weerselo six out of these seven isolectins were detected by mass spectrometry. One of them is an acidic form, which has not been identified before. Our results demonstrate that UDA is encoded by a large gene family.

Paediatric upper gastrointestinal endoscopy: a 2-year review

OBJECTIVE

To review the paediatric upper gastrointestinal endoscopy service in a paediatric department in Hong Kong.

METHODS

Records of all endoscopies undertaken in this department from May 1995 to January 1996 were retrieved and analysed.

RESULTS

The commonest indication for upper endoscopy was dyspepsia with 88% positive histological findings. Helicobacter pylori (H. pylori) was found in 25% of this group of children.

CONCLUSION

Paediatric upper gastrointestinal endoscopy service is invaluable in a paediatric department by providing useful diagnostic information which would otherwise be missed.

Positive selection induces CD4 promoter and enhancer function

Developmental expression of the CD4 gene in mature T cells is controlled by at least four transcriptional control elements: a promoter, two enhancers and a silencer. In this report we use a transgenic approach to study the mechanisms in which these elements interact to convey appropriate tissue- and cell-specific expression at all stages of T cell development. Our data indicate that the control of CD4 gene expression requires the interaction of multiple elements functioning in different combinations at different stages of T cell development. Expression of the CD4 gene in immature CD4+CD8+ thymocytes requires a third enhancer element located in the 3' flanking region of the CD4 gene. Interestingly, the CD4 promoter and proximal/distal enhancers first begin to function at the HSAlo CD69lo H-2Khi CD4 single-positive stage; cells of this phenotype are believed to have survived positive selection. These data indicate that the CD4 promoter and late enhancer elements are induced by positive selection; thus, the final maturation process is an active event that requires the initiation of a novel program of gene expression.

Formation of NADP(H) analogs of tobacco-specific nitrosamines in rat liver and pancreatic microsomes

The metabolism of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and its metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), was examined in rat pancreatic microsomes. No pyridine N-oxidation or alpha-hydroxylation were observed in these preparations. However, one unidentified metabolite of NNAL (unknown A) and two unknown metabolites of NNK (unknowns B and C) were formed. These metabolites were also detected in rat liver microsomal incubations of NNK and NNAL. Studies using [5-3H]-NNK and [Me-3H]NNK demonstrated that the metabolites contained both the pyridyl and methyl portions of the parent compound. Similar results were obtained with NNAL. Formation of unknown C required active microsomes, NADP+, and an NADPH regenerating system. The regenerating system was not required for the formation of NNAL unknown metabolite A or NNK unknown metabolite B. Chemical characterization of unknowns A and B by NMR, UV, and electrospray ionization MS demonstrated that they are NADP+ analogs in which the nicotinamide portion has been replaced by NNAL or NNK, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol adenosine dinucleotide phosphate [(NNAL)ADP+] and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone adenosine dinucleotide phosphate [(NNK)ADP+]. Unknown C was identified as (NNK)ADPH. Both (NNK)ADP+ and (NNK)ADPH were formed from NNK while only (NNAL)ADP+ was produced from NNAL. These NADP+ derivatives were also formed when porcine brain NAD+ glycohydrolase was incubated with NADP+ and NNK or NNAL. These results indicate that NNK and NNAL are substrates for rat liver and pancreatic microsomal NAD+ glycohydrolase-catalyzed transglycosylation reactions.