Involvement of an ATP-dependent carboxylase in a CO2-dependent pathway of acetone metabolism by Xanthobacter strain Py2

The metabolism of acetone by the aerobic bacterium Xanthobacter strain Py2 was investigated. Cell suspensions of Xanthobacter strain Py2 grown with propylene or glucose as carbon sources were unable to metabolize acetone. The addition of acetone to cultures grown with propylene or glucose resulted in a time-dependent increase in acetone-degrading activity. The degradation of acetone by these cultures was prevented by the addition of rifampin and chloramphenicol, demonstrating that new protein synthesis was required for the induction of acetone-degrading activity. In vivo and in vitro studies of acetone-grown Xanthobacter strain Py2 revealed a CO2-dependent pathway of acetone metabolism for this bacterium. The depletion of CO2 from cultures grown with acetone, but not glucose or n-propanol, prevented bacterial growth. The degradation of acetone by whole-cell suspensions of acetone-grown cells was stimulated by the addition of CO2 and was prevented by the depletion of CO2. The degradation of acetone by acetone-grown cell suspensions supported the fixation of 14CO2 into acid-stable products, while the degradation of glucose or beta-hydroxybutyrate did not. Cultures grown with acetone in a nitrogen-deficient medium supplemented with NaH13CO3 specifically incorporated 13C-label into the C-1 (major labeled position) and C-3 (minor labeled position) carbon atoms of the endogenous storage compound poly-beta-hydroxybutyrate. Cell extracts prepared from acetone-grown cells catalyzed the CO2- and ATP-dependent carboxylation of acetone to form acetoacetate as a stoichiometric product. ADP or AMP were incapable of supporting acetone carboxylation in cell extracts. The sustained carboxylation of acetone in cell extracts required the addition of an ATP-regenerating system consisting of phosphocreatine and creatine kinase, suggesting that the carboxylation of acetone is coupled to ATP hydrolysis. Together, these studies provide the first demonstration of a CO2-dependent pathway of acetone metabolism for a strictly aerobic bacterium and provide direct evidence for the involvement of an ATP-dependent carboxylase in bacterial acetone metabolism.

Common alternative gene alterations in adult malignant astrocytomas, but not in childhood primitive neuroectodermal tumors: P 16ink4 homozygous deletions and CDK4 gene amplifications

Alterations in P16ink4 or in the gene encoding one of its ligands, cyclin-dependent kinase 4 (CDK4), have been reported in human glioma cell lines and primary tumors but not in primitive neuroectodermal tumors (PNETs), the most common malignant brain tumor of childhood. In this study the authors have examined DNA from 20 primary PNETs in children and from 20 malignant astrocytomas to assess the frequency of P16ink4 and CDK4 gene alterations associated with each type of tumor. Southern hybridization analysis revealed homozygous P16ink4 deletions in one (5%) of 20 PNETs and in seven (35%) of 20 malignant astrocytomas. The CDK4 gene amplification was evident in two additional astrocytomas, but not in any of the PNETs. In total, nine astrocytomas (45%) exhibited homozygous P16ink4 deletion or CDK4 gene amplification, but only one PNET (5%) demonstrated either gene alteration. These results indicate that the incidence of P16ink4 and CDK4 gene alterations in these two groups of tumors is different and suggest distinct pathogenetic etiologies may be associated with each neoplasm.

Effect of surface-attached heparin on the response of potassium-selective electrodes

Heparin (or hydrolyzed heparin) was covalently attached on the surface of derivatized cellulose triacetate membranes, which were subsequently impregnated with the potassium-selective ionophore valinomycin. The resulting ion-selective electrodes presented near-Nernstian response to potassium and had selectivity coefficients of the same order of magnitude as those of conventional poly-(vinyl chloride)-based electrodes. It was found that the heparin layer does not alter significantly the response characteristics of the electrodes. The biological activity of the immobilized heparin (or hydrolyzed heparin) was measured in terms of its inactivation of blood coagulation factor Xa. It was found that the covalently anchored hydrolyzed heparin was not biologically active, but the immobilized heparin was able to inactivate factor Xa. Therefore, by covalently attaching heparin on the surface of ion-selective electrodes, electrodes with improved blood compatibility characteristics may be prepared.

Carboxylation of epoxides to beta-keto acids in cell extracts of Xanthobacter strain Py2

A novel enzymatic reaction involved in the metabolism of aliphatic epoxides by Xanthobacter strain Py2 is described. Cell extracts catalyzed the CO2-dependent carboxylation of propylene oxide (epoxypropane) to form acetoacetate and beta-hydroxybutyrate. The time courses of acetoacetate and beta-hydroxybutyrate formaton indicate that acetoacetate is the primary product of propylene oxide carboxylation and that beta-hydroxybutyrate is a secondary product formed by the reduction of acetoacetate. Analogous C5 carboxylation products were identified with 1,2-epoxybutane as the substrate. In the absence of CO2, propylene oxide and 1,2-epoxybutane were isomerized to form acetone and methyl ethyl ketone, respectively, as dead-end products. The carboxylation of short-chain epoxides to beta-keto acids is proposed to serve as the physiological reaction for the metabolism of aliphatic epoxides in Xanthobacter strain Py2.

Body protein in prepubertal children with phenylketonuria

OBJECTIVE

To assess body protein and protein deposition in prepubertal children with phenylketonuria (PKU).

DESIGN

Cross-sectional study with nested longitudinal cohort.

SETTING

A tertiary referral paediatric hospital.

SUBJECTS

37 PKU patients (3.9-11.0 years) and 27 unselected healthy controls (4.0-11.5 years) of whom 29 PKU patients and 17 controls were followed longitudinally.

INTERVENTIONS

All had measurements of height, weight, body fat and total body nitrogen (TBN) by neutron capture analysis; PKU patients and their unaffected siblings (n = 16) also had measurements of four day weighed food record and plasma amino acids by HPLC.

RESULTS

The children with PKU compared with the controls were significantly shorter (height SD score -0.42 +/- 0.89 vs 0.17 +/- 0.94, respectively, P < 0.02) and had a lower TBN (575 +/- 200 vs 710 +/- 215g, respectively, P < 0.02). TBN in the controls was significantly correlated with lean body mass (LBM), weight, height and age (r = 0.97, 0.95, 0.95, 0.88, respectively, P < 0.001). The children with PKU had significantly lower TBN when predicted from LBM, weight and age (93%, 92%, 92% of predicted, respectively), but normal TBN predicted from height (102% of expected). The annual accretion of nitrogen was similar for the PKU and controls (86 +/- 45 and 77 +/- 58 g/y, respectively). There was no difference between the two groups in protein intake or plasma amino acids except for phenylalanine.

CONCLUSION

The children with PKU had a deficit in height and body protein despite a normal to higher accretion of protein. If the deficit occurs early in life, amino acid supplementation and other nutritional practices used at this time need to be reviewed.

Oligonucleotide activation of the type IIe restriction enzyme NaeI for digestion of refractory sites

Certain restriction endonucleases previously shown to exhibit DNA site preferences have a two-site DNA cleavage mechanism. These type IIe restriction endonucleases include NaeI, NarI, EcoRII, HpaII and SacII. Because of this two-site mechanism, it is often difficult or impossible to achieve complete digestion of DNA substrate. Inasmuch as these enzymes are commonly used in molecular biology, a method for enzyme activation to provide complete DNA digestion is useful. We have commercialized such a method for NaeI using a double-stranded oligonucleotide containing a modified NaeI recognition sequence. Cleavage of resistant sites requires the presence of a DNA sequence that is more cleavable to bind the activator site. The regions flanking the recognition site on our NaeI oligonucleotide cause it to serve as this more cleavable sequence. This activates the enzyme to cleave the resistant sequence in the catalytic site, while the oligonucleotide modification does not allow the activator to be depleted during the reaction. Turbo NaeI provides for rapid digestion of sites previously found difficult or impossible to completely cleave and does not interfere with subsequent molecular biology techniques that might be performed downstream on the substrate DNA, such as ligation, end-labeling or nick translation.

Resting energy expenditure in children with phenylketonuria

Reports have suggested that children with phenylketonuria (PKU) weigh more compared with reference data. We found lower body protein and bone mineral density in children with PKU. These children may have a predisposition becoming overweight because of an alteration in body composition, which may lower resting energy expenditure (REE). REE was measured in 30 (15 males, 15 females) children with PKU (aged 9.6 +/- 2.9 y) and in 65 (23 males, 42 females) control children (aged 11.2 +/- 3.1 y). There was a comparable range in body fat within each group (control group: 11-34%; PKU group: 10-34%). The mean REE was similar between the male and female children with PKU (5300 +/- 757 and 4703 +/- 1024 kJ/24 h, respectively) and the control subjects (5306 +/- 969 and 5164 +/- 701 kJ/24 h, respectively). The children with PKU had an REE similar to that predicted from control data (males 102.1 +/- 7.8% of predicted and females 100.2 +/- 8.5% of predicted). This study found no evidence of a reduced REE or of increased weight in children with PKU.

Septic arthritis in a collegiate football player

A 23-year-old collegiate football player reported to the training room the day after a game, complaining of severe pain in his right shoulder. He recalled no significant injury during the game. Physical examination revealed pain, tenderness, and apprehension with all attempts to palpate or move the joint. There was no obvious effusion, redness, or warmth about the shoulder joint. The neurovascular examination was negative, and x-rays revealed no fracture. The patient's temperature was 102 degrees F. The team orthopedist aspirated 10cc of purulent fluid from the joint. Subsequent analysis revealed a white cell count greater than 50,000 mm(3), but no organisms were seen. The diagnosis of septic arthritis was made on the basis of the elevated cell count of the joint aspirate, in conjunction with fever (102 degrees F) and the clinical findings of an excessively painful joint. The patient was admitted for arthroscopic irrigation and debridement of the joint. Cultures subsequently showed a light growth of a Gram-negative organism. The patient was treated initially with intravenous broad-spectrum antibiotics and was ultimately discharged and put on oral antibiotics at the time of discharge. Rehabilitation followed the usual protocol for diagnostic arthroscopy, and the patient made an excellent recovery. He has had no residual sequelae or recurrence of infection.

Volumetric bone mineral density--a potential role in paediatrics

The use of areal bone mineral density (aBMD) in paediatric populations has aroused some concern, as it fails to take the age-related increase in bone thickness into account. We have developed a measure of true bone density, volumetric bone mineral density (vBMD), which is independent of age and height. In order to examine the relationship between growth parameters, aBMD and vBMD, we studied patients with phenylketonuria (PKU, n = 40), chronic renal failure (CRF, n = 27) and chronic asthma (n = 19). aBMD of the femoral neck and the mid-femoral shaft was measured using dual energy X-ray absorptiometry (DXA), vBMD was calculated on the basis of values of bone mineral content and bone dimension provided by DXA, with the assumption that both sites are cylinders. aBMD and vBMD were then compared with the normal reference, expressed as a standard deviation score (SDS). aBMD and vBMD were normal in the femoral neck region of the PKU group, but aBMD, either standardized for age or for height, was low in the femoral shaft region (p < 0.01). In the CRF group, profound growth retardation was seen (mean height SDS, -3.2) and aBMD and vBMD were both low in the femoral shaft region but not in the femoral neck. In the asthma group, aBMD for age was low at both sites, but vBMD did not differ from that seen in normal individuals. We conclude that the true vBMD provides a different interpretation of bone density compared with aBMD and requires further evaluation in paediatrics because of its age and height independence.

Body-composition assessment by dual-energy x-ray absorptiometry in subjects aged 4-26 y

This cross-sectional study describes the body composition of 265 normal subjects (137 males and 128 females) aged 4-26 y determined by dual-energy x-ray absorptiometry (DXA). Lean tissue mass (LTM) and bone mineral content (BMC) increased with age in females until 13.4 and 15.7 y, respectively, and in males until 16.6 and 17.4 y, respectively. A strong relation between LTM and BMC was found for each sex (r = 0.98, P = 0.0001 for males; r = 0.98, P = 0.0001 for females). DXA percent body fat (%BFDXA) increased with age in females (r = 0.52, P < 0.001) but not in males and was higher in females than in males at all ages. Trunk to leg fat ratio (TLFR) was calculated as DXA trunk fat/leg fat. In post-pubertal age the TLFR was higher in males than in females (1.01 +/- 0.23 and 0.75 +/- 0.16, P = 0.001), but there was no sex difference in younger children. DXA weight underestimated scale weight by a mean of 0.83 kg. %BFDXA correlated with %BF by skinfold thickness measurement with good agreement for males but overestimated %BF by skinfold thickness for females. These normative data for body composition demonstrate significant sex differences in all body compartments after the pubertal years.

Oscillopsia and vertical eye movements in Tullio's phenomenon

BACKGROUND

Pure tones stimulated oscillopsia in a 30-year-old man with bilateral hearing loss and Tullio's phenomenon.

DESIGN

The subject's eye movements were recorded with electro-oculography while he was seated with his head stabilized facing a visual array. Pure tones were given in each ear, individually, from 500 to 2000 Hz, 90 to 110 dB. The subject reported the intensity of oscillopsia, if any, during each trial. He was also tested while standing on a force platform and receiving pure tones.

RESULTS

No increased postural sway was found, but oscillopsia and vertical eye movements followed stimulation to the more impaired ear.

CONCLUSIONS

These results support the hypothesis that Tullio's phenomenon is caused by inner ear pathology and suggest that oscillopsia is caused by the occurrence of unplanned vertical eye movements, the perceptual consequences of which were unexpected.

Host resistance to ectoparasites

Examples of immunological reactions to arthropod parasites include responses by hosts to the following stimuli: excretory and secretory antigens produced by myiasis-producing larvae or skin-dwelling (mange) mites salivary antigens of blood-sucking arthropods. In many cases, these are hypersensitivity reactions, which often appear not to produce very deleterious effects on the parasites. However, some reactions--such as those induced by natural infestations with ixodid ticks and certain mange mites--damage the parasites and protect the hosts. Recently, successful vaccines have been devised to protect cattle from Boophilus microplus ticks. The antigens used, which are believed not to be introduced into the host during natural infestations, came from the midgut of the ticks. Such antigens, which are normally 'concealed' from the host, appear to induce 'novel' immunological responses which are difficult for the parasite to combat. Similar 'concealed' antigens have also been investigated in potential vaccines for use against other ectoparasitic arthropods.

CDK4 amplification is an alternative mechanism to p16 gene homozygous deletion in glioma cell lines

Recently, it has been shown that a gene encoding the cyclin-dependent kinase 4 inhibitory protein, p16, is frequently targeted for homozygous deletions in several types of tumor cell lines, including those established from malignant gliomas. Here we have examined 32 glioma cell lines for amplification-associated overexpression of the CDK4 gene as an alternative mechanism for abrogating the growth-regulatory effects of p16. Two of the cell lines revealed high-level expression of CDK4 in association with gene amplification, and this alteration was observed among the 10 cases having intact p16 genes. Consequently, 24 of 32 glioma cell lines revealed one of two alternative genetic alterations, each of which indicates that increased cdk4 kinase activity is important to glial tumor development.

Decreased bone mineral density in children with phenylketonuria

Previous studies have suggested that children with phenylketonuria (PKU) have a reduction in bone mineralization compared with control subjects. To investigate this, bone mineral density (BMD) of the total body (TBMD) was measured in 32 prepubertal children with PKU and in 95 age-matched control subjects. Spine bone mineral density (SBMD) was also recorded in a subset, 24 with PKU and 55 control subjects. The effect of dietary intake on bone mass was assessed in 30 of the children with PKU and in 12 control subjects. In the children with PKU, TBMD and SBMD were significantly lower than in the control subjects after adjustment for height and weight (P = 0.03 and P = 0.003, respectively). The children with PKU had a higher intake of calcium (P < 0.0001), phosphorus (P = -0.0002), and magnesium (P < 0.0001), suggesting that their lower BMD occurred despite an adequate diet based on current recommendations. Further study is needed to establish the cause of this deficit in bone mass and the benefit of additional nutritional support to reverse this problem.

In vitro synthesis of the iron-molybdenum cofactor of nitrogenase. Purification and characterization of NifB cofactor, the product of NIFB protein

The requirement of NIFB activity for the biosynthesis of iron-molybdenum cofactor (FeMo-co) can be satisfied by the addition of the low molecular weight product of NIFB, termed NifB cofactor (NifB-co). NifB-co has been purified to homogeneity by a unique one-step method. Addition of NifB-co into the FeMo-co synthesis system generated nitrogenase activity of 27-32 nmol of ethylene formed/min/nmol of iron. Iron is the only metal detected in the NifB-co. NifB-co-dependent in vitro FeMo-co synthesis is absolutely dependent on the presence of molybdate, homocitrate and active NIFNE protein in the reaction mixture. The cofactor appears to be a small Fe-S cluster synthesized by NIFB, as a precursor of FeMo-co. NifB-co did not display any EPR signal at 4 K in 0-4000 gauss range. A solution of NifB-co is greenish-brown in color, similar to FeMo-co. NifB-co exhibits a broad absorbance between 400 and 700 nm with no distinctive peaks or shoulders. NifB-co is stable to repeated freeze-thaw cycles and is also stable in N-methylformamide, the solvent used for the isolation of FeMo-co. The NifB-co is stable to a 5-min heat treatment at 60 degrees C. The cofactor is extremely O2-labile, with half-life of less then 15 s in air.

Comparison of 10 influenza A (H1N1 and H3N2) haemagglutinin sequences obtained directly from clinical specimens to those of MDCK cell- and egg-grown viruses

PCR was used to amplify and sequence the complete HA1 region of the haemagglutinin (HA)-encoding genes of 10 clinical isolates of influenza virus of the H1N1 or H3N2 subtypes. These sequences were compared to those obtained from viruses isolated from the same specimens after passage in eggs and MDCK cells. Amino acid substitutions in the egg-derived HA sequences were found in nine out of the 10 specimens analysed, whereas seven out of eight of the MDCK-derived HA sequences were identical to those in the corresponding original specimens. Changes in the H1 HA occurred at residues 77a, 196 (also found in the corresponding HA from the MDCK isolate), 225, 226 and 227; changes in the H3 HA occurred at residues 137, 156, 186, 248 and 276. In addition, we have shown that an amino acid change at residue 145 in the HA of the H3 subtype that was previously demonstrated to be egg-selected is now present in circulating strains.

Development of a paediatric indirect calorimeter

An indirect calorimeter was developed to measure resting energy expenditure (REE) and respiratory quotient (RQ) in a clinical paediatric population. The design is suitable for any child spontaneously breathing room air. Measurements are possible from small babies to large hypermetabolic adolescents due to the ability to set and control flow from the patient headbox across the range 2-40 l/min. The calorimeter is mobile, it is electrically safe and the patient interface may be disinfected. An alcohol burning technique, that can emulate a clinical test for children of various sizes, is used to check the system, which has a high level of accuracy across a range of conditions. The indirect calorimeter has been successfully used to measure a large number of children of different sizes.

Outbreaks of summer rotavirus linked to laboratory practices. The National Rotavirus Surveillance System

In temperate regions rotavirus diarrhea is a disease of the cooler months of the year, but little is known about its patterns in the summer. We report on the first year of national surveillance of rotavirus, during which we actively investigated patterns of summer activity. We obtained data on rotavirus testing from 85 laboratories in 48 states, conducted a survey of their testing practices and retested for confirmation positive specimens from laboratories reporting high rates of positivity during the summer. During 1989 participating laboratories reported 4011 specimens tested for rotavirus during July and August, of which 436 (11%) were said to be positive. Most laboratories reported low rates of positivity during these months (median percent positive, 3), but five had very high rates of summer positivity (> 30%). These five laboratories were geographically separated, and neighboring laboratories showed little rotavirus activity. Positive specimens submitted by four of these centers with high rates of summer rotavirus could not be confirmed. A survey of laboratory methods found one commercial assay (TestPack) and two laboratory practices (failure to use controls and involvement of more than six technicians in the testing process) to be associated with high rates of summer positivity. Moderate rates of positivity (11 to 30%) were fond frequently in the southwest during July and August; reference testing of specimens from these laboratories confirmed positivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Coding assignments of the genome of adult diarrhea rotavirus

Adult diarrhea rotavirus (ADRV) has caused epidemics of diarrhea in China since 1982 and remains the only group B rotavirus associated with widespread disease in humans. We recently characterized the proteins of ADRV and have now proceeded to identify the gene segments encoding each protein. Viral RNA transcripts were synthesized in vitro with the endogenous viral RNA polymerase and separated by electrophoresis in agarose. The individual transcripts were translated in a cell-free system using nuclease-treated rabbit reticulocyte lysates. The translation products were compared with polypeptides found in purified virus and were characterized by SDS-PAGE, immunoprecipitation, and Western blot analysis using antisera to double- and single-shelled virions, virus cores, and monoclonal antibodies. Furthermore, individual RNA transcripts were hybridized to total dsRNA to determine their genomic origin. Based on this analysis, the core polypeptides VP1, VP2 and VP3 are encoded by segments 1, 2, and 3, respectively. The main polypeptides in the inner capsid, VP6, and the outer capsid, VP4 and VP7, are encoded by segments 6, 4, and 8 respectively. Segments 5, 7, and 9 code for 60, 45, and 30 kDa nonstructural polypeptides. Two other nonstructural polypeptides (24 and 25 kDa) are derived from gene segment 11. Gene segment 10 codes for a 26 kDa polypeptide that is precipitated with serum to ADRV and may be a structural protein VP9. With this exception, gene coding assignments of ADRV are comparable to those of the group A rotaviruses. Our results have clear implications for further work in cloning, sequencing, and expression genes of ADRV and can provide direction towards understanding the origin and the evolution of this virus.

Identification of cognate genes among heterologous strains of group B rotavirus

The genetic relatedness of group B rotavirus (GBR) strains has previously been documented by hybridization with probes derived from whole genomic sequences, but the relationship of individual genes of heterologous GBR strains has not been evaluated. Definition of cognate GBR genes would facilitate investigation of the determinants of group specificity, serotype identity, and neutralization epitopes. Therefore, we investigated the genetic relatedness of three GBR strains by means of Northern (RNA) blot hybridization with isotopically labeled probes prepared from each of the 11 genes of the IDIR strain of GBR. Under low-stringency conditions, hybridization between each of the IDIR gene probes and genomic RNA from the ADRV strain of GBR was observed. Genomic RNA obtained from a bovine strain of GBR hybridized with 9 of the 11 IDIR gene probes. In most cases, cognate genes of each of the GBR strains appeared to migrate to similar positions following polyacrylamide gel electrophoresis. However, the electropherotype positions of GBR genes 5, 6, and 7 were different for each of the three GBR strains. Identification of these genomic segments among GBR strains should prove helpful in future evaluations of GBR structure and function.