Simulium damnosum s.l.: identification of inducible serine proteases following an Onchocerca infection by differential display reverse transcription PCR

Vector-derived proteases are thought to be key to the regulation of filarial infections in Simulium damnosum s.I. To identify proteases of S. damnosum s.I. induced by infection with Onchocerca ochengi, a PCR-based differential display technique was used. By combining this method with homology-based serine protease primers transcripts can be detected from S. damnosum s.I. RNA.

Mixed chimerism following bone marrow transplantation for severe combined immunodeficiency: a study by DNA fingerprinting and simultaneous immunophenotyping and fluorescence in situ hybridisation

We report a girl with severe combined immunodeficiency (SCID) who had a paternal T-depleted bone marrow transplant (BMT) when 11 months old. Engraftment was documented but karyotyping of marrow cells 1 year after BMT showed recipient metaphases (XX) only. However, she remained clinically well and further analysis y karyotyping of PHA-cultured peripheral blood mononuclear cells (PBMC) showed donor metaphases (XY) only. DNA fingerprinting confirmed mixed chimerism in the peripheral blood. The granulocytes were of recipient origin and the PBMC of mixed origin, the donor proportion of which increased after culture with PHA. Using simultaneous immunophenotyping and fluorescence in situ hybridisation (FISH) with chromosomes X and Y-specific probes, circulating T cells were demonstrated to be of donor origin whereas B cells and myeloid cells were mostly of recipient origin.

Screening for urothelial malignancies by cytologic analysis and flow cytometry in a community urologic practice: a prospective study

A prospective study was initiated to compare the ability of flow cytometry and cytologic analysis to detect malignant cells in urine obtained at the time of cystoscopy. The population studied consisted of patients from general urologic practices who were undergoing cystoscopy in a single community hospital. Over a 1-yr period, 335 specimens from 317 patients were studied. Nineteen biopsy-proven urothelial malignancies were identified. Cytologic examination of urine obtained at the time of cystoscopy was positive in seven of these cases, and an aneuploid population of cells was identified by flow cytometry in three cases. All three cases of high-grade transitional cell carcinoma and carcinoma in situ were correctly identified by the combination of cytologic examination and flow cytometry; however, only four of 16 low-grade superficial papillary transitional cell carcinomas were recognized cytologically, with only one being aneuploid. The combination of cytologic analysis and flow cytometry did not increase the diagnostic sensitivity above that achieved with cytologic testing alone (overall sensitivity, 37%). We conclude that flow cytometry and cytologic analysis, either individually or in combination, are too insensitive for use in a routine screening program for urothelial malignancy in a community hospital setting because of the inability of either method to detect low-grade transitional cell carcinomas reliably.

Synchronous intermittent mandatory ventilation modes compared with patient triggered ventilation during weaning

The efficacy of combining rate and pressure reduction during weaning by synchronous intermittent mandatory ventilation (SIMV) were compared with weaning by patient triggered ventilation (PTV) (pressure reduction alone) in two randomised trials. Regardless of ventilation mode, pressure was reduced to the same level according to the size of the infant. In the first trial, the SIMV rate was also reduced progressively to a minimum of 20 breaths/minute, and in the second to five breaths/minute. Forty premature infants aged 15 days of age or less were randomly allocated into each trial. No significant differences were found in the first trial between ventilation modes in either the duration of weaning or the number of infants in whom weaning failed. In the second trial, the duration of weaning was shorter by PTV than by SIMV (median 24 hours, range 7-432 v 50 hours, range 12-500; p < 0.05); weaning failed in two infants in the PTV group and in five in the SIMV group. It is concluded that weaning by a combination of pressure and rate reduction, such as can be achieved during SIMV, offers no significant advantage over pressure reduction alone.

Volume delivery during positive pressure inflation--relationship to spontaneous tidal volume of neonates

Volume delivery by positive pressure inflation was determined in 20 premature infants and 10 infants born at term on days 1 and 2. The spontaneous tidal volume, respiratory rate and inspiratory to expiratory (I:E) ratio were measured daily in the first week of life in an additional group of 20 infants born prematurely. Measurements were made using a pneumotachograph only when the infants were stable and had acceptable blood gases for at least 2 h. There was variability between individuals but the median delivered volume by positive pressure ventilation ranged between 4.9 and 6.1 ml/kg on days 1 and 2 and within the groups of different maturity. There was no significant difference in the results of infants born prematurely or at term or when studied on days 1 or 2. The median spontaneous tidal volume during the first week of life varied between 5.4 and 6.7 ml/kg; respiratory rate between 72 and 80 breaths/min and I:E ratio from 0.67 to 0.77. Postnatal age had no significant effect on the results. These results suggest volume delivery by positive pressure inflation during a stable period of ventilation is similar to the spontaneous tidal volume.

Use of the polymerase chain reaction in the detection of AML1/ETO fusion transcript in t(8;21)

BACKGROUND

t(8;21)(q22;q22), found in acute myeloid leukemia (AML) and occasionally in myelodysplasia (MDS), results in the fusion of the AML1 gene on 22q22 to the ETO gene on 8q22, generating a chimeric AML1/ETO transcript, which is a molecular marker of the translocation.

METHODS

Reverse transcription-polymerase chain reaction (RT-PCR), with two pairs of nested AML1 and ETO primers, was used to amplify the AML1/ETO fusion transcript. The Kasumi-1 cell line was used as a positive control.

RESULTS

RT-PCR has a sensitivity of 0.0001% (10(-6)), corresponding to detection of 0.5 picograms of leukemic RNA in the presence of 0.5 micrograms of normal RNA. Using this approach, patients with t(8;21) (three patients with de novo AML, one with therapy-related AML, and one patient with myelodysplasia) yielded the same 222 base pair PCR product, suggesting that the breakpoints occurred at the same AML1 and ETO introns as previously reported. Three patients were still PCR-positive when in complete remission after chemotherapy and two experienced relapse. However, in another three patients with t(8;21) who were in remission for 2 months, 2 years, and 3 1/2 years, respectively, PCR was negative.

CONCLUSION

RT-PCR is a sensitive method of detection of t(8;21), and is useful in the monitoring of minimal residual leukemia. As the junction of AML1/ETO appears to be constant, RT-PCR may offer a quick and accurate diagnosis of t(8;21).

DNA analysis of Huntington's disease in southern Chinese

Allelic frequencies of RFLPs at loci closely linked to the HD gene, D4S95, D4S91, D4S141, and D4S90, were determined in 13 Huntington's disease (HD) patients from nine Chinese families and 129 normal subjects. These were similar for non-HD and HD chromosomes and the HD gene in Chinese is associated with multiple haplotypes. Hence the HD gene probably arose independently in the background haplotypes of the Chinese population. The heterozygosity rates for the two most useful RFLP sites are 0.659 for D4S95-AccI VNTR and 0.494 for D4S141-HindIII. (CAG)n repeat numbers ranged from 12 to 27 in 174 normal chromosomes. In 52 meiotic recombinations, the (CAG)n repeats were stably inherited in normal families. In HD families, 12 of 13 HD patients had expanded (CAG)n repeats of 40 to 58. Additionally, 10 asymptomatic family members had expanded (CAG)n repeats and the inheritance of the expanded repeat was unstable in these families.

High frequency oscillation, respiratory activity and changes in blood gases

Spontaneous respiratory activity during high frequency oscillation (HFO) and its relationship to changes in blood gases on transfer to HFO has been assessed. Eighteen infants were studied, median gestational age 27 weeks and postnatal age 1 day. Simultaneous measurements of changes in oesophageal and airway pressure, flow and volume were made during a period of conventional ventilation and then during HFO. From these recordings, the infants' spontaneous respiratory rate during the two ventilatory techniques were calculated. Arterial blood gases were measured immediately before and after a 30-min period of HFO. All the infants were breathing during conventional ventilation (median rate of 55 breaths/min). On transfer to HFO, the respiratory rate of the whole group decreased to a median of 23 breaths/min (P < 0.001), but only five infants became apnoeic. The changes in respiratory rate did not relate significantly to changes in PaCO2. Oxygenation deteriorated in four of the five apnoeic infants and in the two infants who became agitated during HFO. In the remaining 11 infants, whose median respiratory rate was 28 breaths/min (range 15-77) during HFO, oxygenation improved by a median of 12 mmHg (range 4-42). We conclude that, in the majority of infants, spontaneous respiratory activity during HFO is compatible with improvements in blood gases.

Intragenic dinucleotide repeats in factor VIII gene for the diagnosis of haemophilia A

Two multi-allelic microsatellite polymorphisms within the factor VIII gene were studied in 138 Chinese subjects. The allele sizes detected were higher than those found in Caucasian populations, whereas the heterozygosity rates were lower, being 0.5370 for intron 13 and 0.4444 for intron 22 repeats respectively. Their usefulness in diagnosis was compared to other intragenic and extragenic RFLPs, using previous data on the same 31 unrelated haemophilia A families. These intragenic microsatellite repeat polymorphisms were only informative for 18/31 families (58%); however, with the combined use of all existing RFLPs, the cumulative informativeness would be 100%.

Ultrasound measurement of placental thickness to detect pregnancies affected by homozygous alpha-thalassaemia-1

Homozygous alpha-thalassaemia-1, a common cause of hydrops fetalis, is usually diagnosed invasively. We measured placental thickness by ultrasound at 10-21 weeks' gestation in 231 at-risk pregnancies. 60 were affected (by DNA analysis). The sensitivity and specificity in detecting affected pregnancies at cut-off of mean placental thickness plus 2 SD before 12 weeks' gestation were 0.72 (95% CI 0.52-0.93) and 0.97 (0.9-1.0). After 12 weeks sensitivity increased to 0.95 (0.89-1.0) and by 18 weeks reached 1.0 (0.60-0.99) without change in specificity. Selection of pregnancies at risk by measurement of placental thickness will reduce the number of invasive diagnostic procedures.

Inspiratory and expiratory times for infants ventilator-dependent beyond the first week

The aim of this study was to determine optimum inspiratory and expiratory times to be used for ventilation of infants older than one week of age. Each infant was studied at a rate of 30 breaths/min (inspiratory times (TI) of 1.0, 0.67 and 0.5 s with expiratory times (TE) of 1.0, 1.33 and 1.5 s, respectively) and at a rate of 60 breaths/min (TI 0.5, 0.33 and 0.25 s and TE 0.5, 0.67 and 0.75 s, respectively). Arterial blood-gases were examined after 20 min on each setting. Fifteen infants with a median gestational age of 27 weeks were studied at a median postnatal age of 9 days and 10 infants with a median gestational age of 27 weeks at a median postnatal age of 24 days. All infants had type I chronic lung disease. Oxygenation did not consistently improve as TI was prolonged, elevating mean airway pressure but, particularly in older infants, was better at TI > or = 0.5 s compared with TI < 0.5 s. In both groups, carbon dioxide elimination was better at 60 than at 30 breaths/min. Thus we suggest that in infants fully ventilator-dependent beyond the first week of life, an inspiratory and expiratory time of 0.5 s should be used as the first choice.

Psychosocial impact of Huntington's disease on Hong Kong Chinese families

Twenty-eight asymptomatic relatives from 7 Chinese families with Huntington's disease (HD) received psychosocial assessment. One third of these subjects (n = 9) had symptoms of anxiety and depression that warranted a Present State Examination (PSE) diagnosis. One quarter of these subjects (n = 8) would contemplate suicide if their predictive testing indicated a high risk of having the disease. This suicidal risk was associated with a PSE diagnosis of depression and a stress-coping repertoire with a high proportion of coping strategies of the avoidance type at the time of interview. Early and close liaison with these subjects for the detection of mental symptoms and provision of counselling on a balanced and positive coping style is essential.

Influence of lung function and reflex activity on the success of patient-triggered ventilation

The influence of lung function and reflex activity on the success of patient-triggered ventilation (PTV) has been determined. Lung function was assessed by measurement of compliance using a single breath technique. Reflex activity was assessed by measurement of the strength of Hering Breuer reflex indicated by the degree of prolongation of expiration following end inspiratory occlusion. PTV was considered to have failed if the infant became apnoeic or required an increased level of respiratory support. Twenty premature infants (median gestational age 29 weeks) in the recovery stage of respiratory distress, were studied at a median postnatal age of 2.5 days. PTV failed ultimately in six infants, although compliance of the respiratory system of that group did not differ significantly from the rest of the cohort, their Hering Breuer reflex was significantly weaker (P < 0.01). In addition, the infants in whom PTV failed were significantly more immature and of lower birthweight (P < 0.01) compared with those in whom it succeeded. We conclude that failure of PTV is more likely in immature infants who have a weak Hering Breuer reflex.

Comparison of weaning by patient triggered ventilation or synchronous intermittent mandatory ventilation in preterm infants

Forty preterm infants were entered into a randomized controlled trial to compare the efficacy and duration of weaning by patient triggered ventilation (PTV) to that of synchronous intermittent mandatory ventilation (SIMV). Infants were randomized during recovery from respiratory distress once ventilator rate had been reduced to 40 breaths per minute; weaning during PTV was by reduction in ventilator pressure only, whereas infants randomized to SIMV were weaned by reduction in rate only. Weaning failed in 12 infants, 6 from each group, the 12 infants were more immature than those in whom weaning succeeded (p < 0.01). Overall, the duration of weaning did not differ significantly between the PTV and SIMV groups.

Disease severity and optimum mean airway pressure level on transfer to high frequency oscillation

The aim of this study was to assess whether the severity of the infant's lung disease determined the most appropriate change in mean airway pressure (MAP) level to use on transfer from conventional ventilation to high frequency oscillation (HFO). In addition, we wished to assess whether the oscillatory frequency employed affected gas exchange. Ten premature infants with respiratory distress syndrome (RDS) were studied at a mean postnatal age of 1.5 days. During HFO, the infants were studied at a MAP equivalent of that used during conventional ventilation (baseline MAP), then at 2 and 5 cmH2O above baseline at 10 Hz. At the MAP identified as optimum, that is, the one associated with the best oxygenation, the infants were then studied at 10, 15 and 20 Hz. Each oscillatory setting was maintained for 20 minutes after which time arterial blood gases were measured. Prior to transfer to the oscillator, the peak inspiratory pressure was recorded, the P(A-a)O2 calculated and compliance of the respiratory system (Crs) measured. In nine infants, the optimum baseline MAP was +5 cmH2O. Oxygenation at that level was better than on conventional ventilation (P < 0.05), but there was no significant change in CO2 elimination. The optimum MAP was related to the peak pressure during conventional ventilation (P < 0.01) and inversely related to Crs (P < 0.01). There was no significant relationship with the P(A-a)O2. At the optimum MAP, the only significant effect of frequency was an impairment of oxygenation at 20 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)

A novel haemophilia B defect due to partial duplication of the factor IX gene

A patient with mild FIX deficiency was found to have partial duplication of the 3' region of the gene, giving, in addition to the a normal gene, another piece of DNA containing exons 5', 6', 7' and 8' and the intervening sequences. Cloning and sequencing of the junction region revealed that crossover occurred at nt 31927 in the 3' untranslated region of one chromosome/chromatid and nt 10640 in intron 4 of the other. No homology or topoisomerase specific sequences were observed in the crossover region. PCR and sequencing of illegitimate FIX transcripts from the patient's lymphocytes showed at least three different species of mRNAs. Translation of two of these 'novel' mRNAs should result in truncated proteins. Possibilities for the splicing of the mature mRNA are offered to explain the translation of a normal-size FIX protein, which was the only product demonstrated on Western blot analysis.

Huntington's disease in Hong Kong Chinese: epidemiology and clinical picture

In a territory-wide survey of Huntington's disease (HD) in the Chinese population of Hong Kong, 20 patients from 11 families were identified from 1984 to 1991, giving a low period prevalence of 3.7 per 10(6) population. Six patients had died by 1991, hence the point prevalence was even lower, being 2.5 per 10(6) population. The male to female ratio was 3:1. No paternal transmission effect on the age of onset was observed. Apart from these differences, the clinical and pathological features were similar to those seen in the West.

High frequency oscillation for preterm infants with severe respiratory failure

High frequency oscillation (HFO) as rescue treatment for preterm infants with severe respiratory failure has been assessed and prognostic factors identified. Thirty six infants with a median gestational age of 27 weeks were studied. Immediately before transfer to HFO, the infants were receiving an inspired oxygen concentration of > or = 85% and/or a mean airway pressure of > or = 12 cm H2O and had a median alveolar-arterial oxygen gradient (A-aDO2) of 73.28 kPa (range 49.34-89.91). Seventeen infants subsequently died. Comparison of those 17 with the remaining 19 infants demonstrated that respiratory distress syndrome and persistent fetal circulation were associated with a significantly better outcome than pulmonary airleak. The A-aDO2 after two and six hours on HFO was significantly higher in those infants who survived compared with those who died. We conclude that a diagnosis of pulmonary airleak and failure to show early improvement in respiratory status indicate a poor prognosis when HFO is used as rescue treatment.

Pituitary stone: two cases of densely calcified thyrotrophin-secreting pituitary adenomas

Calcification is a well recognized but relatively uncommon feature of prolactin-secreting, growth hormone-secreting and non-functional pituitary tumours. It varies in extent, but rarely exceeds a tiny amount histologically or radiologically. Thyrotroph adenomas are the rarest of the secretory pituitary tumours, accounting for less than 1% of cases, and partial calcification of such lesions has been reported in only three cases. We describe two patients in whom the clinical and biochemical features indicated the presence of a TSH-secreting adenoma and radiology demonstrated a large 'pituitary stone'. One patient, a 59-year-old female, initially presented with hyperthyroidism, aged 18, and was rendered euthyroid by two subtotal thyroidectomies before a pituitary lesion was suspected, over 20 years later. Autonomous secretion of thyrotrophin was demonstrated by dynamic tests, and the failure of exogenous T3 to reduce the serum TSH. In the absence of tumour expansion and compressive symptoms, pituitary surgery was not undertaken. At the age of 56, she developed symptoms of intermittent ataxia and diplopia, culminating in a focal seizure, and was found on CT scan to have, in addition to the pituitary lesion, a parasagittal meningioma. This was successfully removed at craniotomy. In the second patient, a 42-year-old male, the finding of hyperthyroidism in association with an elevated TSH concentration led to the discovery of a pituitary stone which was removed transethmoidally, together with surrounding adenomatous tissue which stained positively for TSH on immunocytochemistry.(ABSTRACT TRUNCATED AT 250 WORDS)

The performance of a new valveless ventilator at rates of up to 250 bpm

The efficacy of a new ventilator, incorporating a valveless pneumatic exhalation circuit, at rates of up to 250 bpm was first assessed in the laboratory. Using this ventilator the effect of fast rate ventilation on blood gases of infants with acute respiratory distress was then examined. Infants were studied at three rates: 60, 125 and 250 bpm. Peak inflating and positive end expiratory pressure, inspiratory: expiratory ratio and inspired oxygen were kept constant. The laboratory study demonstrated that as ventilator rate was increased the delivered volume fell, but even at 250 bpm the delivered volume was 7 ml. In the clinical study, oxygenation at 250 bpm was not significantly different from that at 60 bpm, but significantly lower than at 125 pbm. Carbon dioxide levels were significantly lower at 250 bpm that at 60 bpm, but did not differ significantly from that at 125 bpm. We conclude increasing ventilator rate from 125 to 250 bpm is not advantageous for infants ventilated for acute respiratory distress.

The effect of frequency on carbon dioxide levels during high frequency oscillation

The aim of this study was to assess if, during high frequency oscillation (HFO), a frequency of 10 or 15 Hz was associated with lower carbon dioxide levels. Twelve infants were recruited, median gestational age 27 weeks. All infants were studied at both frequencies, applied in random order and the carbon dioxide level checked after 30 minutes on each frequency. Carbon dioxide levels were lower in 10 of the 12 infants at 10 compared to 15 Hz (p < 0.004) and, in the study population, overall were significantly lower at 10 Hz (p < 0.05). The difference in paCO2 levels at the two frequencies, however, was small, thus these results suggest the clinician should rely primarily on changes in oscillatory amplitude, rather than frequency, to effect changes in carbon dioxide levels.

False non-paternity in a family for prenatal diagnosis of beta-thalassaemia

Initial screening for the common beta-thalassaemia mutations with allele-specific oligonucleotide probes in an at-risk family suggested non-paternity. Subsequent DNA fingerprinting of the members proved otherwise. The mother had a codon 41/42 frameshift mutation and the father's defect, determined by direct sequencing of PCR-amplified beta gene, was a codon 43 nonsense mutation. In the affected children, the close proximity of these two defects resulted in the absence of a hybridization signal to the normal probe in that region and a wrong assumption of homozygosity for the codon 41/42 mutation. The non-reactivity of the father's amplified DNA to the codon 41/42 thalassaemic probe accounted for the initial wrong conclusion of non-paternity. Since prior screening for beta-thalassaemia mutations is done in all prenatal diagnosis programmes and concomitant inheritance of these two defects is relatively common in the Chinese, this 'artefact' of false non-paternity is worth noting.

Comparison of helium dilution and nitrogen washout measurements of functional residual capacity in premature infants

Comparison has been made of measurements of functional residue capacity (FRC) by a helium gas dilution (He) and a nitrogen washout (N2) technique. Twenty infants (median gestational age, 29.5 weeks) were studied at a median postnatal age of 25 days. No infant was oxygen dependent. The coefficient of repeatability of FRC (He) was 6.4 mL/kg and of FRC (N2), 6.3 mL/kg. The coefficient of repeatability of the two methods combined was 13.8 mL/kg. In 10 infants the results of two techniques differed by more than 20% of the mean FRC; those infants were born at a significantly earlier gestation than the rest of the cohort (P < 0.01). We conclude that, except in very immature infants, techniques for measuring FRC (He) and FRC (N2) yield reproducible and comparable results in convalescent premature infants.

Randomised trial of methods of extubation in acute and chronic respiratory distress

Sixty infants (median gestational age 29 weeks) with acute and 60 infants (median gestational age 25 weeks) with chronic respiratory distress were randomised to be extubated either directly into a headbox or onto 3 cm H2O nasal continuous positive airway pressure (CPAP). Our aim was to test the hypothesis that extubation onto nasal CPAP rather than directly into a headbox was more likely to be associated with successful extubation in infants with acute rather than chronic respiratory distress. Overall the failure rate of extubation was approximately 33%, with no significant difference between the infants with acute and chronic respiratory distress. There was no significant difference in the failure rate of extubation among infants randomised to receive nasal CPAP or headbox oxygen in either the acute or chronic respiratory distress groups.

Detection of immunoglobulin gene rearrangement in lymphoid malignancies of B-cell lineage by seminested polymerase chain reaction gene amplification

Seminested polymerase chain reaction (PCR) was used to amplify the DNA fragments of the complementarity-determining region 3 of the immunoglobulin (Ig) gene heavy chain from the malignant cell specimens of patients with leukemias and lymphomas of B-cell lineage. Two different pairs of primers were used sequentially. Twenty of the 27 (74%) acute lymphoblastic leukemia (ALL) patients, 14 of 19 (74%) chronic lymphocytic leukemia (CLL) patients and eight of 20 (40%) non-Hodgkin's lymphoma (NHL) patients, who had rearrangement of the Ig gene heavy chain by Southern analysis, were positive by the seminested PCR. False-negative results appeared to occur more commonly in cases of lymphoma. The PCR analysis was also less likely to be positive if one-stage PCR studies with either pair of primers were both negative. The seminested PCR technique was found to have a high sensitivity of detecting malignant cells at the level of 0.02%. The clinical application of this assay needs to be investigated further.

Determinants of oxygenation during high frequency oscillation

Two studies are reported in which the aim was to assess whether oxygenation on transfer to or during high frequency oscillation (HFO) was influenced by the mean airway pressure (MAP) level. Sixteen infants, median gestational age 28 weeks, were recruited into the first study and 14 with a median gestational age of 29 weeks into the second. In the initial study, blood gases were measured immediately before and 30 min after transfer to HFO and comparison made of those infants in whom oxygenation did or did not improve. In the second study the infants were studied at two MAP levels, 2 and 5 cmH2O, above that used during conventional ventilation (baseline MAP) and at two frequencies (10 and 15 Hz), arterial blood gases were measured after 20 min on each setting. In the initial study, on transfer to HFO, oxygenation improved by a median of 21 mmHg in eight infants, but was either unchanged or deteriorated (n = 7) in the other eight infants, the median impairment in oxygenation was by 17 mmHg. The infants in whom oxygenation improved had required a significantly higher MAP during conventional ventilation than the rest of the study group. In the second study, increasing the MAP from 2 to 5 cmH2O above baseline resulted in a significant increase in oxygenation, which was significantly greater at 10 rather than 15Hz. Infants whose MAP remained below 13 cmH2O had impaired oxygenation during HFO compared to that experienced during conventional ventilation. The results of these two studies demonstrate that the MAP level during HFO is an important determinant of oxygenation.

Respiratory status and diuresis following treatment with dexamethasone

The effect of dexamethasone therapy on fluid balance, lung function and requirement for respiratory support has been assessed. Ten premature infants were studied, they had a median gestational age of 28 weeks. None of the infants had any improvement in the respiratory status for 48 h prior to commencing dexamethasone. Fluid balance, pulmonary function and requirement for respiratory support were measured 12 h prior to and for 36 h after receiving dexamethasone. There were no significant changes in fluid input over the study period, but urine output increased significantly after 12 h of dexamethasone therapy (P < 0.02). Compliance of the respiratory system only significantly improved after 36 h of dexamethasone therapy (P < 0.03), this was associated with a significant change in the inspired oxygen concentration (P < 0.05). We conclude that the improvement in respiratory status resulting from dexamethasone therapy is preceded by a diuresis.

The effect of frequency and mean airway pressure on volume delivery during high-frequency oscillation

The performance of a commercially available oscillator (SensorMedics 3100) at different frequencies was assessed. A frequency response curve of a pneumotachograph system was constructed and this was used to measure the volume delivered by the oscillator to a lung model. The volume delivered by a constant diaphragm displacement was demonstrated to be inversely proportional to the frequency, but unaffected by increasing mean airway pressure from 15 to 25 cm H2O. The volume delivered during high frequency oscillation (HFO) was then assessed in 8 infants, median gestational age 29 weeks. The infants were studied at two frequencies, 10 and 15 Hz, both of which were used at two levels of mean airway pressure (MAP): 2 and 5 cm H2O above the MAP level previously used during conventional ventilation. The delivered volume was not significantly different at the two MAP levels, but was significantly greater at 10 than 15 Hz at both MAP levels (P < 0.03); at MAP +2 cm H2O above baseline the reduction in delivered volume was from a median of 1.54 mL/kg (range, 0.88-3.12) at 10 Hz to 1.18 mL/kg (range, 0.65-4.5) at 15 Hz. These results suggest that higher frequencies would require an increase in the oscillator displacement if effective gas exchange is to be maintained.

Prenatal quantitation of number of X-chromosomes by slot blot hybridization and autoradiography

OBJECTIVE

To study the use of slot blot hybridization as a method of prenatal quantification of the number of X-chromosomes in chorionic villi samples.

METHOD

DNA of chorionic villi from fetuses with karyotypes of 46,XY; 45,XO; 47,XXX; 69,XXX and 48,XXXX were extracted, slot blotted and hybridized to the following radioactive probes: beta 0.9, FVIII, pY3.4 and pBLUR. DNA of chorionic villi from five other fetuses with unknown karyotypes were similarly blotted and hybridized. Autoradiography with pre-exposed films was carried out and the density of each of the hybridized bands was scanned by a laser densitometer.

RESULTS

It was found that with increasing amounts of DNA in the samples, the intensity of the bands hybridized with FVIII and beta 0.9 probes increased proportionately. However, the intensity of the bands obtained with the probes pY3.4 and pBLUR (probes containing multiple repeat sequences) varied little with increasing DNA concentrations. The ratios of radioactivity obtained for the two probes FVIII/beta 0.9, were well correlated with the number of X-chromosomes in the samples. Calculations of the FVIII/beta 0.9 ratio for the five samples with the unknown karyotypes gave a correct prediction of the number of X-chromosomes in each case.

CONCLUSION

Slot blot hybridization can be used as a method of prenatal quantitation of the number of X-chromosomes in chorionic villi samples. The method could be useful for rapid prenatal diagnosis of other numerical chromosomal abnormalities.

Vitamin A levels at birth of high risk preterm infants

Vitamin A levels were measured shortly after birth in preterm infants at high risk of developing chronic lung disease (CLD). Eleven infants, median gestational age 24 weeks, developed CLD. Their results were compared to 11 infants who, although they required mechanical ventilation for at least 48 hours, did not develop CLD. The median gestational age of this latter group was 30 weeks (range 27-35). The median vitamin A level of the infants who developed CLD was 0.62 umol/l (range 0.41-0.95), which was significantly higher than the median level of the infants who did not develop CLD, which was 0.36 umol/l (range 0.13-0.89). We conclude preterm infants who develop CLD are not predisposed to develop that complication by low vitamin A levels at birth.

Haemophilia: strategies for carrier detection and prenatal diagnosis

In 1977 WHO published in the Bulletin a Memorandum on Methods for the Detection of Haemophilia Carriers. This was produced following a WHO/WFH (World Federation of Haemophilia) Meeting of Investigators in Geneva in November 1976, and has served as a valuable reference article on the genetics of haemophilia. The analyses discussed were based on phenotypic assessment, which, at that time, was the only procedure available. The molecular biology revolution in genetics during the 1980s made enormous contributions to our understanding of the molecular basis of the haemophilias and now permits precise carrier detection and prenatal diagnosis. WHO and WFH held a joint meeting on this subject in February 1992 in Geneva. This article is the result of these discussions.

Randomised controlled trial of weaning by patient triggered ventilation or conventional ventilation

A group of preterm infants (n = 40) were entered into a randomised controlled trial to compare the duration and efficacy of weaning by patient triggered ventilation (PTV) or conventional ventilation. Once recovery from respiratory distress had begun, enabling the ventilator rate to be reduced to 40 breaths/min, infants were randomised to either regime. Infants randomised to PTV were weaned by reduction in ventilator pressure only, whereas infants randomised to conventional ventilation were weaned by reduction in ventilator rate only. Only one infant required re-ventilation within 24 h of extubation; this infant had been weaned by conventional ventilation. Three infants, all of less than 28 weeks gestation, did not tolerate weaning by PTV and were subsequently weaned conventionally. The duration of weaning was analysed according to the original randomisation allocation and was significantly shorter in the PTV group, being a median of 30 h (mean 39, range 3-186) compared to a median of 61 h (mean 65, range 15-262) in the conventional group, P < 0.02. We conclude PTV is the more advantageous form of weaning in preterm infants of greater than 27 weeks gestational age.

Vitamin A status in preterm and term infants at birth

Vitamin A status was determined in infants born at term or prematurely to assess if vitamin A levels at birth were related to gestational age. Vitamin A levels were measured in cord blood samples from 13 infants born at term and in blood samples obtained within two hours of birth in 26 preterm infants (median gestational age 31 weeks, range 27-35). None of the preterm infants developed chronic lung disease. The vitamin A levels of the term infants (median 0.71 mumol/l, range 0.34 to 1.27) were significantly higher than those of infants born preterm (median 0.35 mumol/l, range 0.12 to 1.22), p < 0.01. Vitamin A levels correlated significantly with gestational age (vitamin A level = 0.024 gestational age (weeks) -0.23, r = 0.39, p < 0.02. We thus conclude that gestational age must be taken into account when interpreting vitamin A levels.

Vitamin A levels and feeding practice in neonates with and without chronic lung disease

Infants with chronic lung disease (CLD) have been demonstrated to have low vitamin A levels. The aim of this study was to assess factors which influenced this association. Vitamin A levels of infants born at less than 32 weeks gestational age with and without CLD were determined and related to feeding practice. The infants with CLD had statistically significantly lower vitamin A levels on days 21 to 30 and days 31 to 40. From day 11 onwards, the median Vitamin A levels were less than 60% of the minimum acceptable level for a healthy child or adult. Infants with CLD required significantly longer mechanical ventilation and parenteral nutrition than controls and there was a significant positive correlation between duration of mechanical ventilation and parenteral nutrition (r = 0.83). Infants with CLD received significantly less vitamin A supplementation than the infants without CLD. Our results thus suggest that feeding practice explains the association of CLD and vitamin A deficiency in preterm infants.

Evaluation of triggering systems for patient triggered ventilation for neonates ventilator-dependent beyond 10 days of age

The performance of two triggering systems was compared during patient triggered ventilation (PTV) of infants ventilator-dependent beyond 10 days of age. Ten infants were studied who had a median gestational age of 26.5 weeks and a postnatal age of 15.5 days. PTV was administered via the SLE ventilator and the two triggering systems, an airway pressure monitor and the MR10 respiration monitor, were used in random order each for 30 min. The airway pressure trigger had a superior performance in that, although it did not differ significantly in delivered inflation volume or sensitivity to the MR10 respiration monitor, it had a shorter trigger delay (P < 0.01). Oxygenation improved in eight of the ten infants on the airway pressure trigger, but only in three on the MR10 respiration monitor. The reduction in PaCO2 was greater during PTV with the airway pressure trigger compared with the MR10 respiration monitor (P < 0.01). We conclude that the airway pressure trigger has a superior performance compared to the MR10 respiration monitor trigger in infants who are ventilator-dependent beyond 10 days of age.

Neonatal complications of extreme prematurity in mechanically ventilated infants

Previous data have suggested that neonatal complications amongst preterm ventilated infants increase with decreasing gestational age and thus are likely to be greatest among ventilated infants of less than 28 weeks gestational age. The aim of this study was to test that hypothesis, thus we report the neonatal complications of 175 extremely preterm mechanically ventilated infants (gestational age less than or equal to 28 weeks). Of the infants 152 were ventilated because of respiratory distress syndrome (RDS) or respiratory distress of severe prematurity, 41% of these infants died. Amongst infants with RDS or respiratory distress of extreme prematurity, mortality was significantly increased in infants of gestational age less than or equal to 24 weeks and birth weight less than or equal to 1000 g. In this group 20% developed a pneumothorax, and mortality was inversely related to gestational age. In infants with RDS, 43% developed a periventricular haemorrhage and 37% were still oxygen-dependent at 28 days of age; neither of these complications was significantly related to birth weight or gestational age. Of infants with RDS 38% developed a patent ductus arteriosus and 16% developed retinopathy of prematurity. These data suggest that even amongst very immature infants there has been an impressive reduction in the neonatal complications of mechanical ventilation.

Closed-circuit TV: an effective patient education tool

Patient education is well accepted to be an integral component of professional nursing practice. Although most nurses value patient teaching, the reality of the nursing shortage demands that innovative strategies be utilized to plan, implement and evaluate in-hospital patient education programs. Advances in computer technology have made closed-circuit television (CCTV) an attractive option for hospitals to fulfil their patient education mandate. As a delivery system, CCTV can be of considerable value. But as is true of other instructional media used to supplement educational efforts, CCTV also provides many traps that can limit its effectiveness. The biggest danger is the misuse of the tool by attempting to replace rather than supplement human interaction during the education process. This paper provides practical suggestions for the creative use of CCTV as a teaching tool to enhance patient education efforts. Pitfalls inherent in planning and implementing a CCTV system will be discussed.

Detection of immunoglobulin gene rearrangement in B-cell lymphomas by polymerase chain reaction gene amplification

This is a report on our attempt to use polymerase chain reaction (PCR) to detect rearrangement of the immunoglobulin gene in the tissue specimens obtained from 30 patients with non-Hodgkin's lymphomas. There were 20 B-cell lymphomas and 10 T-cell. All 20 B-cell lymphomas but none of the 10 T-cell lymphomas had JH rearrangement by Southern analysis. Two pairs of primers (V670/OL-4 and VH26/OL-4) were designed to amplify the CDR3 region of the immunoglobulin gene heavy chain. The PCR analysis was positive using either one or both pairs of primers in 11 of the the 20 cases (55 per cent) of B-cell lymphomas which all had positive rearrangement by Southern analysis. The two pairs of primers seemed to produce complementary results as the specimens may be positive to one pair but negative to the other. The false negative rate of 45 per cent is however much higher than the respective figures of 18 per cent and 0 per cent observed in our patients with acute lymphoblastic leukemia and chronic lymphocytic leukemia in a previous study. Peripheral blood and bone marrow biopsy specimens obtained at the time of initial diagnosis were available from 10 patients with B-cell lymphomas whose lymph node biopsy specimens at the time of diagnosis were positive by both Southern analysis and PCR. All these peripheral blood and marrow specimens had no microscopic evidence of involvement by lymphoma cells and JH rearrangement was not detected by Southern analysis. However, rearranged bands identical to that of the lymph node biopsy specimen were detected by PCR in the peripheral and marrow blood of one of them. This PCR technique has been shown to have a sensitivity of 0.1 per cent in our previous report and may be more useful than morphology alone or Southern analysis in detecting minimal lymphomatous involvement in the peripheral blood and bone marrow at the time of initial diagnosis. Further clinical correlation is required to confirm the finding.

Positive end expiratory pressure in acute and chronic respiratory distress

The optimum level of positive end expiratory pressure (PEEP) was determined in 16 infants with respiratory distress syndrome (median gestational age 29 weeks, median postnatal age 1 day) and in 16 infants with chronic respiratory distress (median gestational age 25 weeks, median postnatal age 15 days). All infants were studied at a PEEP sequence of 3, 0, 3, 6, and 3 cm H2O, all other ventilator parameters being kept constant. Each PEEP level was maintained for 20 minutes and at the end of each period arterial blood gas was checked. During acute respiratory distress syndrome there were no significant changes in oxygenation but arterial carbon dioxide tension (PaCO2) significantly decreased from a mean of 4.93 kPa at 3 cm H2O to 4.40 kPa at 0 cm H2O and increased to a mean of 5.87 kPa at 6 cm H2O. In the infants with chronic respiratory distress, oxygenation fell from a mean of 8.66 kPa at 3 cm H2O to 6.40 kPa at 0 cm H2O and improved at 6 cm H2O to a mean of 10.50 kPa. There were no significant changes in PaCO2. We conclude that addition of PEEP, up to 6 cm H2O, may be useful even after the first week of life. High levels of PEEP, however, have previously been reported, in certain infants, to result in circulatory disturbance. It is therefore important to assess the use of 6 cm H2O PEEP in a controlled study of longer term clinical outcome.

Lung function and the Hering Breuer reflex in the neonatal period

Lung function and the occurrence of the Hering Breuer reflex during the neonatal period has been investigated. To assess the effect of extrauterine and intrauterine maturation on the strength of the reflex both preterm and term infants were recruited. Ten preterm infants, born at a median gestational age of 29.5 weeks (range 27-34) were studied serially over the first four weeks of life and 10 term infants were studied at a median postnatal age of 1.5 days (1-4). All of the infants were recruited from the neonatal unit and initially had had some form of respiratory distress. Respiratory rate, tidal volume and compliance were measured and end inspiratory occlusion performed in an attempt to provoke the Hering Breuer reflex. The Hering Breuer reflex was provoked in all infants on all occasions. There was no difference in the strength of the reflex between the preterm and term infants or preterm infants studied at different postnatal ages. All infants studied regardless of maturity or postnatal age had non-compliant lungs and a rapid respiratory rate. These data suggest a lack of intrauterine and extrauterine maturation of the Hering Breuer reflex in the neonatal period amongst infants with non-compliant lungs.

Long-term survival of a baby with homozygous alpha-thalassemia-1

Triplets born to a Chinese woman consisted of 2 healthy boys and a girl with hemoglobin Bart's hydrops syndrome. The girl with hemoglobin Bart's hydrops syndrome, confirmed by gene analysis to be homozygous for alpha-thalassemia-1, survives for 27 months at the time of reporting. The dilemma in sustaining her life and the availability of other therapeutic options are briefly discussed. This is the third case report of homozygous alpha-thalassemia-1 with long-term survival.

Severe localised pulmonary interstitial emphysema--decompression by selective bronchial intubation

We report three infants (26-28 weeks gestational age) in whom selective bronchial intubation was associated with successful decompression of severe localised pulmonary interstitial emphysema, uniquely in two cases this involved intubation of the left main bronchus. Pulmonary interstitial emphysema did not recur despite maintenance of selective intubation for only 48 hours or less in all three cases.

Comparison of different rates of artificial ventilation for preterm infants ventilated beyond the first week of life

The effect on blood gases of different ventilator rates in preterm infants ventilated beyond the first week of life was assessed. Seventeen infants, median gestational age 25 weeks, were studied at median postnatal age of 11 days. The infants were ventilated through a set sequence of rates: 30, 60, 30, 100 and 30 breaths per min (bpm), each rate being maintained for 20 min. Peak and positive end expiratory pressure and I:E ratio (1:1) were unchanged at each rate and mean airway pressure was kept constant by altering flow as necessary. No significant change in oxygenation was demonstrated at either rates of 60 or 100 bpm compared to 30 bpm. PaCO2 levels were, however, significantly reduced at 60 bpm (P less than 0.001) compared to 30 bpm; but this improvement in PaCO2 was not seen at 100 bpm. These results suggest that increasing ventilator rate higher than 60 bpm in the majority of infants ventilated after the first week of life is not advantageous.

Airway pressure triggered ventilation for preterm neonates

The usefulness of airway pressure triggered ventilation for the preterm newborn has been assessed using a new patient triggered valveless ventilator, the SLE 2000 infant ventilator (SLE 2000). This ventilator performs well at fast rates with no inadvertent positive end expiratory pressure (PEEP) even at rates of 150 breaths per minute (bpm). The ventilator is triggered by a change in airway pressure equal to or exceeding 0.5 cmH2O. If the infant fails to achieve the change in airway pressure which will trigger the ventilator the infant is ventilated at the back-up rate which is predetermined in conventional mode prior to commencing PTV. Infants were ventilated for one hour on a conventional neonatal ventilator, then for one hour on the SLE 2000 in conventional mode without changing the ventilator settings and finally for one hour on the SLE 2000 in patient triggered mode. Arterial blood gases were checked at the end of each hour. During patient triggered ventilation (PTV) the peak pressure, inspiratory time and inspired oxygen concentration were the same as those used during conventional mode. Simultaneous recordings were made of flow, volume, ventilator and oesophageal pressure change, from this recording the trigger delay during PTV was calculated. The trigger delay, being the time lag from the start of spontaneous inspiration, indicated by the negative deflection in the oesophageal pressure trace, and the onset of the ventilator breath. Thirteen infants were included in the study, median gestational age 32 weeks (range 25-35) and birthweight 1640 g (range 838-3038). All were being ventilated for respiratory distress syndrome (RDS) and were 4 days of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Rearrangement of immunoglobulin, T-cell receptor, and bcl-2 genes in malignant lymphomas in Hong Kong

The pattern of malignant lymphomas in the Hong Kong Chinese population is characterized by a low incidence of Hodgkin's disease and follicular lymphomas. The authors studied the immunoglobulin (Ig), T-cell receptor (TCR), and bcl-2 gene rearrangement in 62 cases of malignant lymphoma in this population by Southern blot hybridization. Two cases of Hodgkin's disease showed no rearrangement of the Ig and TCR genes. All 42 cases of B-cell lymphoma had Ig heavy chain (JH) rearrangement with or without additional rearrangement of the light chains (C kappa and C lambda). One case of diffuse B-cell lymphoma had additional T-cell receptor beta-chain (C beta) rearrangement. Sixteen of 18 cases of T-cell lymphoma had C beta rearrangement, and one case of T-lymphoblastic lymphoma had additional JH rearrangement. Two of eight (25%) cases of follicular lymphoma but only one of the 34 (2.9%) cases of diffuse B-cell lymphoma had bcl-2 rearrangement that was detected by pFL-1 probe. None of the 62 cases showed bcl-2 rearrangement using the pFL-2 probe. In conclusion, the Ig and TCR gene rearrangement pattern of the lymphomas found in Hong Kong correlates well with the T-cell and B-cell lineage, which is similar to reports in the white population. However, the incidence of bcl-2 gene rearrangement in follicular B-cell lymphoma is lower than that reported in the US but comparable with that in Japan.