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.

Conversion of bovine pancreatic DNase I to a repair endonuclease with a high selectivity for abasic sites

Bovine pancreatic deoxyribonuclease I (DNase I) is a nuclease of relatively low specificity which interacts with DNA in the minor groove. No contacts are made between the protein and the major groove of the nucleic acid. DNase I is structurally homologous to exonuclease III, a DNA-repair enzyme with multiple activities. One of the main differences between the two enzymes is the presence of an additional alpha-helix in exonuclease III, in a position suggestive of interaction with the major groove of DNA. Recombinant DNA techniques have been used to add 14 amino acids, comprising the 10 amino acids of the exonuclease III alpha-helix flanked by a glycine rich region, to DNase I. The polypeptide has been inserted after serine 174, an amino acid on the surface of DNase I corresponding to the location of the extra alpha-helix in exonuclease III. The recombinant protein, DNase-exohelix, has been purified and its catalytic activities towards DNA investigated. The recombinant protein demonstrated a high selectivity for endonucleolytic cleavage at abasic sites in DNA, a property of exonuclease III but not native DNase I. Thus the insertion of 14 amino acids at Ser174, converts DNase I to an exonuclease III-like enzyme with DNA-repair properties.

[Frontotemporal dementia in a young woman with apparent schizophrenia]

In a woman aged 35 who for the last 5 years had been suffering from conduct disorders, especially kleptomania, compulsive cleaning behaviour and affective neglect of her children, psychodiagnostic examination initially suggested a delusional disorder. In view of the gradual aggravation of bizarre behaviour, the diagnosis 'schizophrenic psychosis of the hebephrenic type' was made; supplementary examination revealed no abnormalities. Finally, in view of the ununderstood and progressive behavioural changes, the diagnosis was reconsidered; on the basis of clinical findings, SPECT examination and results of repeated CT of the brain, the diagnosis of 'frontotemporal dementia, type Pick' was made.

Human theta class glutathione transferase: the crystal structure reveals a sulfate-binding pocket within a buried active site

BACKGROUND

Glutathione S-transferases (GSTs) comprise a multifunctional group of enzymes that play a critical role in the cellular detoxification process. These enzymes reduce the reactivity of toxic compounds by catalyzing their conjugation with glutathione. As a result of their role in detoxification, GSTs have been implicated in the development of cellular resistance to antibiotics, herbicides and clinical drugs and their study is therefore of much interest. In mammals, the cytosolic GSTs can be divided into five distinct classes termed alpha, mu, pi, sigma and theta. The human theta class GST, hGST T2-2, possesses several distinctive features compared to GSTs of other classes, including a long C-terminal extension and a specific sulfatase activity. It was hoped that the determination of the structure of hGST T2-2 may help us to understand more about this unusual class of enzymes.

RESULTS

Here we present the crystal structures of hGST T2-2 in the apo form and in complex with the substrates glutathione and 1-menaphthyl sulfate. The enzyme adopts the canonical GST fold with a 40-residue C-terminal extension comprising two helices connected by a long loop. The extension completely buries the substrate-binding pocket and occludes most of the glutathione-binding site. The enzyme has a purpose-built novel sulfate-binding site. The crystals were shown to be catalytically active: soaks with 1-menaphthyl sulfate result in the production of the glutathione conjugate and cleavage of the sulfate group.

CONCLUSIONS

hGST T2-2 shares less than 15% sequence identity with other GST classes, yet adopts a similar three-dimensional fold. The C-terminal extension that blocks the active site is not disordered in either the apo or complexed forms of the enzyme, but nevertheless catalysis occurs in the crystalline state. A narrow tunnel leading from the active site to the surface may provide a pathway for the entry of substrates and the release of products. The results suggest a molecular basis for the unique sulfatase activity of this GST.

Covalent immobilization of glucose oxidase on the surface of polyaniline films graft copolymerized with acrylic acid

Glucose oxidase (GOD) was covalently immobilized on the electroactive polyaniline (PAN) film with surface-grafted acrylic acid (AAc) polymer through the amide linkage formation between amino groups of GOD and the carboxyl groups of the grafted AAc polymer chains in the presence of a water-soluble carbodiimide. The surface structure and composition of the graft-modified and enzyme-functionalized PAN films were characterized by angle-resolved X-ray photoelectron spectroscopy (XPS). The amounts of immobilized GOD and its activity were also investigated. It was shown that the amount of immobilized GOD increased linearly with the concentration of surface-grafted AAc polymer chains. The decrease in activity of the immobilized GOD was considered to be due to, among other factors, the reduced accessibility of glucose molecules to the active sites of the enzyme and the conformational change of the GOD molecules as a result of the covalent immobilization. However, the immobilized enzyme was less sensitive to thermal inactivation as compared to that of the free form. The optimum pH value of GOD was not affected by the immobilization reaction and the pH stability range was considerably widened. The immobilized GOD also exhibits a significantly improved stability during storage in buffer solution over that of the free enzyme.

Preliminary X-ray crystallographic studies of a newly defined human theta-class glutathione transferase

Human theta-class glutathione S-transferases (GST's) appear to play a critical role in the metabolism of a variety of environmental pollutants but in some cases the products of the reaction are carcinogenic. Crystals of a human theta-class GST, namely hGSTT2-2, have been grown from polyethylene glycol by the hanging-drop vapour-diffusion method. The crystals belong to the trigonal space group P3121 with cell dimensions of a = b = 94.0 and c = 120.5 A. They contain two monomers in the asymmetric unit and diffract to 3.0 A resolution.

Spontaneous corneal perforation in premature infants

Spontaneous corneal perforation in premature infants not due to birth trauma is a rare event, with only 8 cases reported in the literature. We recently encountered a case of spontaneous corneal perforation in an extremely premature infant born at 26 weeks of gestation. The mechanism leading to this event was corneal exposure resulting in corneal epithelial defect. Clinical evidence of secondary infection ensued and this led to cornea thinning, descemetocoele formation and subsequent perforation with extrusion of intraocular contents. Although other mechanisms were responsible in the previously reported cases, we feel that exposure keratopathy leading to this complication poses a potential hazard to all premature infants. An awareness among care givers of this potential complication together with avoidance of exposure keratopathy in this group of patients is paramount in preventing this visually catastrophic event.

Vocal cord dysfunction: two case reports

Vocal cord dysfunction is an uncommon condition characterised by adduction of vocal cords that can masquerade as or coexists with bronchial asthma. The glottic dysfunction is due to a functional (non-organic) cause. If unrecognised, incorrect diagnosis may result in patients being unnecessarily treated as refractory or severe asthma with high doses of corticosteroid. This may result in unwarranted steroid toxicity. Clues that should raise clinical suspicion to the diagnosis of vocal cord dysfunction include lack of response to bronchodilators, poor reproducibility of spirometric indices due to inconsistent effort and truncation of the inspiratory limb of the flow-volume loop. Definitive diagnosis is made by direct visualisation of the vocal cords during an attack. We report two patients with vocal cord dysfunction and review the literature on this disorder.

An epidemiological study of developmental dysplasia of the hip in infants in Singapore

The incidence of congenital dislocation of the hip (CDH) in Singapore and Malaysia has been reported as being lower than in the West. In our hospital, we have seen an increasing number of congenital hip dislocation as well as dysplastic hips. We undertook a prospective study from December 1989 to December 1994 of 20,000 live births. The neonates were all screened by a consultant neonatologist and the findings were confirmed by a consultant paediatric orthopaedic surgeon. All babies had plain X-rays at 3 months and an acetabular index (AI) of 30 degrees or more was considered dysplastic. All babies with positive signs were followed up for 1 year and again had radiographs taken at 1 year. Comparison of plain X-rays and ultrasound assessment in a subgroup of 130 neonates showed that 64% of patients with AI > 20 degrees had hip dysplasia by ultrasonographic (alpha angle < 60 degrees) The incidence of dysplastic hips was 16.8 per 1000 live births. The overall incidence of neonates with dislocated hips was 4.7 per 1000 live births. The Malays were most affected with an incidence of 5.4 per 1000 live births. The incidence of developmental dysplasia of the hip in Singapore is higher than previously reported, with the Malays having the highest incidence. A significant number of babies with clicking hips have radiological evidence of acetabular dysplasia (AI > 30 degrees). One-third of the babies' hips were still dysplastic at 1 year of age. A well-organised screening programme with experienced examiners has proved to be useful in making early and accurate clinical diagnosis.

Efficacy of bidirectional fiber-optic phototherapy for neonatal hyperbilirubinemia

OBJECTIVE

To evaluate the efficacy of fiber-optic phototherapy using the standard Ohmeda Biliblanket, a large version, double standard Biliblankets, and conventional phototherapy using daylight fluorescent lamps in full-term, healthy infants with nonhemolytic hyperbilirubinemia.

METHODS

Full-term, healthy infants with nonhemolytic hyperbilirubinemia (bilirubin concentration, >255 micromol/L or 222 micromol/L at <48 hours of age) were allocated randomly to one of four modes of phototherapy: standard fiber-optic mat (Ohmeda Biliblanket), a large version, double standard Biliblankets, and conventional phototherapy. Bilirubin levels were monitored every 12 hours. Exposure was stopped when bilirubin levels were less than 185 micromol/L, the minimum duration being 24 hours.

RESULTS

A total of 171 infants were studied; 42 were exposed to standard fiber-optic phototherapy, 43 to large fiber-optic phototherapy, 42 to double-fiber-optic phototherapy, and 44 to conventional phototherapy. Durations of exposure were 87.05 +/- 6.09 (SEM), 82.57 +/- 5.84, 64.85 +/- 5.43, and 62.61 +/- 3.74 hours, respectively; the 24-hour decline rates were 10.26% +/- 1.84%, 14. 50% +/- 1.53%, 21.82% +/- 1.71%, and 19.00% +/- 1.65%, respectively; the overall decline rates over the whole exposure period were 0.47% +/- 0.03%, 0.52% +/- 0.04%, 0.71% +/- 0.05%, and 0.75% +/- 0.04% per hour, respectively. The efficacy of double-fiber-optic phototherapy and conventional phototherapy was similar and significantly better than that of the large fiber-optic mat and the standard fiber-optic mat in duration, 24-hour decline rate, and overall decline rate. The large mat was slightly better than the standard-size mat with regard to 24-hour decline rate and overall decline rate, but this difference was not significant. Failure of phototherapy occurred only in the large fiber-optic mat group (3 of 43) and the standard fiber-optic mat group (4 of 42); none occurred in the other two groups, but differences not statistically significant. The nursing personnel were more comfortable with single fiber-optic phototherapy, which caused no initial disturbance to the swaddled infants as did conventional phototherapy, but found double-fiber-optic phototherapy difficult to use.

CONCLUSION

For efficacy of fiber-optic phototherapy in full-term infants to be comparable to that of our conventional phototherapy, the light dose of the standard mats needs to be doubled.

Copper Sites in Copper-Exchanged ZSM-5 for CO Activation and Methanol Synthesis: XPS and FTIR Studies

Cu-ZSM-5 samples with various Cu(+)/Cu(2+) ratios have been successfully prepared in three different methods and studied by XPS and FTIR. Cu(+) ions are found, by XPS, to mainly exist in the samples prepared by solution ion exchange and microwave solid-state reaction exchange. On the basis of the chemical shift of the Al 2p core level to a higher binding energy [Al(species II)], with the atomic ratio of Cu(+)/Al(species II) being approximately one, and the vanishing of the IR band at 3640 cm(-)(1) due to copper exchange, it is suggested that Cu(+) ions locate in the open channels of the ZSM-5 framework and bind to mixed (Si- and Al-) bridged oxide ion. From the ZSM-5 pore structure consideration, as well as from the observed decrease in the IR intensity ratio of bands 550/450 cm(-)(1) with enhanced Cu(2+) loading, it is also suggested that Cu(2+) ions are a predominant Cu species in solid-state reaction exchanged Cu-ZSM-5 samples and exist as a CuO cluster in small cages as well as in open channels. The IR bands at 907 and 964 cm(-)(1) are identified as zeolite asymmetric internal vibration perturbed by exchanged Cu(2+) and Cu(+) ions, respectively. Cu ions in Cu-ZSM-5 samples can be reduced to Cu(0) by CO adsorption at room temperature. The IR bands at 2128, 2158, and 2176 cm(-)(1) are observable and ascribed to the CO adsorbed on Cu(0), Cu(+), and Cu(2+) sites, respectively. Methanol formation from syngas over Cu-ZSM-5 is observed at 250 degrees C and 2 MPa.

Chylothorax: case report and review of literature

Chylothorax is a relatively uncommon condition. We report a case of a 53-year-old Chinese man with chylothorax who presented with cough, breathlessness, loss of weight and generalised lymphadenopathy. He was initially diagnosed as having tuberculosis based on histology and cultures of the cervical lymph node. However, immunophenotyping of the pleural fluid by flow cytometry showed the presence of a monoclonal B cell population with Kappa light chain expression suggesting an underlying lymphoproliferative disorder. A repeat lymph node biopsy showed malignant lymphoma (follicular small cleaved type). In spite of aggressive measures which included bilateral tube thoracostomy drainage, a low fat diet, medium chain triglyceride diet, total parenteral nutrition, chemotherapy and mediastinal irradiation, his chylothorax persisted. Hence, we report a patient with persistent chylothorax and generalised lymphadenopathy who was subsequently diagnosed to have concurrent tuberculosis and malignant lymphoma. The literature on chylothorax is reviewed.

Homology model for the human GSTT2 Theta class glutathione transferase

A tertiary model of the human GSTT2 Theta class glutathione transferase is presented based on the recently solved crystal structure of a related thetalike isoenzyme from Lucilia cuprina. Although the N-terminal domains are quite homologous, the C-terminal domains share less than about 20% identity. The model is used to consolidate the role of Ser 11 in the active site of the enzyme as well as to identify other residues and mechanisms of likely catalytic importance. The T2 subfamily of theta class enzymes have been shown to inactivate reactive sulfate esters arising from arylmethanols. A possible reaction pathway involving the conjugation of glutathione with one such sulfate ester, 1-menaphthyl-sulfate, is described. It is also proposed that the C-terminal region of the enzyme plays an important role in allowing substrate access to the active site.