Enhanced internal dynamics of a membrane transport protein during substrate translocation

Conformational changes are essential for the activity of many proteins. If, or how fast, internal fluctuations are related to slow conformational changes that mediate protein function is not understood. In this study, we measure internal fluctuations of the transport protein lactose permease in the presence and absence of substrate by tryptophan fluorescence spectroscopy. We demonstrate that nanosecond fluctuations of alpha-helices are enhanced when the enzyme transports substrate. This correlates with previously published kinetic data from transport measurements showing that millisecond conformational transitions of the substrate-loaded carrier are faster than those in the absence of substrate. These findings corroborate the hypothesis of the hierarchical model of protein dynamics that predicts that slow conformational transitions are based on fast, thermally activated internal motions.

Role of ureaplasma urealyticum in lung disease of prematurity

AIM

To examine the role of Ureaplasma urealyticum colonisation or infection in neonatal lung disease.

METHODS

Endotracheal aspirates from ventilated infants less than 28 weeks of gestation were cultured for U urealyticum and outcomes compared in infants with positive and negative cultures.

RESULTS

U urealyticum was isolated from aspirates of 39 of 143 (27%) infants. Respiratory distress syndrome (RDS) occurred significantly less often in colonised, than in non-colonised infants (p=0.002). Multivariate logistic regression analysis showed that in singleton infants, ureaplasma colonisation was the only independent (negative) predictor of RDS (OR 0.36; p=0. 02). Both gestational age (OR 0.46; p=0.006) and isolation of U urealyticum (OR 3.0; p=0.05) were independent predictors of chronic lung disease (CLD), as defined by requirement for supplemental oxygen at 36 weeks of gestational age. Multiple gestation was also a major independent predictor of RDS and CLD.

CONCLUSIONS

Colonisation or infection with ureaplasma apparently protects premature infants against the development of RDS (suggesting intrauterine infection). However, in singleton infants, it predisposes to development of CLD, independently of gestational age. Treatment of affected infants after birth is unlikely to significantly improve the outcome and methods are required to identify and treat the women with intrauterine ureaplasmal infection, before preterm delivery occurs.

Retinopathy of prematurity in infants < 32 weeks' gestation at birth in New South Wales in 1993 and 1994

OBJECTIVE

To study the incidence and severity of retinopathy of prematurity (ROP) in infants < 32 weeks' gestation.

DESIGN

Review of the records maintained in the New South Wales Neonatal Intensive Care Unit Study (NICUS) database on infants admitted to the neonatal intensive care units (NICU) in NSW from 1 January 1993 to 31 December 1994.

RESULTS

In the more premature infants, 23-26 weeks' gestation, 65% developed ROP (102 of 157 examined for ROP). Forty-four infants (28%) developed severe ROP (Stage >/= 3 ROP), 19 infants (12.1%) required cryo/laser therapy and one infant (0.6%) in this group had a retinal detachment. One hundred and fifty-seven of 159 surviving infants (98.7%) were examined for ROP. In the infants 27-28 weeks' gestation, 38.3% developed ROP (103 of 269 examined for ROP). Fifteen infants (5.6%) developed severe ROP, seven infants (2. 6%) required cryo/laser therapy for threshold ROP and three infants (1.1%) in this group had a retinal detachment. Two hundred and sixty-nine of 299 surviving infants (90%) were examined for ROP. In the infants 29-31 weeks' gestation, 10.8% developed ROP (48 of 443 examined for ROP). Six infants (1.4%) developed severe ROP, one infant (0.2%) required cryo/laser therapy for threshold ROP and no infant in this group had a retinal detachment. However, only 443 of 681 surviving infants (65.1%) in this group were examined for ROP. Of the four infants with detached retinas, one was a 25 week gestation infant weighing 840 g, two were 27 weeks' gestation weighing 960 and 980 g and one infant was a 28 week gestation infant weighing 620 g. No infant developed Stage 5 ROP.

CONCLUSION

In the more mature infants 29-31 weeks' gestation, the rate of ROP is low, although severe ROP still occurs. However, only 65.1% of these infants were examined for ROP and we should be diligent in screening for ROP in the sicker infants in this group. The incidence of severe ROP as well as the rate of cryo/laser therapy in premature infants 23-26 weeks' in NSW has not changed since the increases seen in the early 1990s. Retinal detachment also occurs in the infants 27-28 weeks' gestation and it is important that all these infants are screened for ROP.

Retinopathy of prematurity in infants < 32 weeks' gestation at birth in New South Wales in 1993 and 1994

OBJECTIVE

To study the incidence and severity of retinopathy of prematurity (ROP) in infants < 32 weeks' gestation.

DESIGN

Review of the records maintained in the New South Wales Neonatal Intensive Care Unit Study (NICUS) database on infants admitted to the neonatal intensive care units (NICU) in NSW from 1 January 1993 to 31 December 1994.

RESULTS

In the more premature infants, 23-26 weeks' gestation, 65% developed ROP (102 of 157 examined for ROP). Forty-four infants (28%) developed severe ROP (Stage ≥ 3 ROP), 19 infants (12.1%) required cryo/laser therapy and one infant (0.6%) in this group had a retinal detachment. One hundred and fifty-seven of 159 surviving infants (98.7%) were examined for ROP. In the infants 27-28 weeks' gestation, 38.3% developed ROP (103 of 269 examined for ROP). Fifteen infants (5.6%) developed severe ROP, seven infants (2.6%) required cryo/laser therapy for threshold ROP and three infants (1.1%) in this group had a retinal detachment. Two hundred and sixty-nine of 299 surviving infants (90%) were examined for ROP. In the infants 29-31 weeks' gestation, 10.8% developed ROP (48 of 443 examined for ROP). Six infants (1.4%) developed severe ROP, one infant (0.2%) required cryo/laser therapy for threshold ROP and no infant in this group had a retinal detachment. However, only 443 of 681 surviving infants (65.1%) in this group were examined for ROP. Of the four infants with detached retinas, one was a 25 week gestation infant weighing 840 g, two were 27 weeks' gestation weighing 960 and 980 g and one infant was a 28 week gestation infant weighing 620 g. No infant developed Stage 5 ROP.

CONCLUSION

In the more mature infants 29-31 weeks' gestation, the rate of ROP is low, although severe ROP still occurs. However, only 65.1% of these infants were examined for ROP and we should be diligent in screening for ROP in the sicker infants in this group. The incidence of severe ROP as well as the rate of cryo/laser therapy in premature infants 23-26 weeks' in NSW has not changed since the increases seen in the early 1990s. Retinal detachment also occurs in the infants 27-28 weeks' gestation and it is important that all these infants are screened for ROP.

New animal model to evaluate testicular blood flow during testicular torsion

BACKGROUND/PURPOSE

Unilateral testicular torsion is known to cause infertility because of damage to the contralateral testis. Testicular damage has been attributed to many different mechanisms, one of which is altered contralateral blood flow. In our experiment, in an effort to identify the reason for contralateral testicular injury, the authors developed an accurate method of measuring blood flow in both testes before, during, and after unilateral torsion.

METHODS

Four- to 6-week-old piglets weighing 4 to 6 kg were studied. The animals were anesthetized, intubated, ventilated, and catheterized for vascular access. Piglets were assigned randomly to a sham group or a group undergoing 360 degrees or 720 degrees torsion of the left testis (n = 5 per group) for 8 hours, after which it was untwisted. Data were collected at baseline (T = 0), 8 hours of torsion (T = 8), and 1 hour after detorsion (T = 9). Mean arterial blood pressure and heart rate were monitored continuously. Testicular blood flow was determined using radiolabeled microspheres. Blood flow data were evaluated by analysis of variance.

RESULTS

In the 360 degrees torsion group, blood flow changes were insignificant during torsion and after detorsion. In the 720 degrees torsion group, blood flow to the twisted testis was reduced significantly, whereas the contralateral testis was unaffected. One hour after detorsion, blood flow to both testes was increased significantly.

CONCLUSIONS

The authors describe a new animal model to evaluate testicular blood flow during and after testicular torsion. Increased blood flow after detorsion may be the cause of testicular damage in patients with unilateral testicular torsion.

Effect of unilateral testicular torsion on blood flow and histology of contralateral testes

BACKGROUND/PURPOSE

Infertility occurs in 25% of patients after unilateral testicular torsion; hence, the authors examined hemodynamic and histological changes in both testes after acute testicular torsion in neonatal piglets.

METHODS

The animals were anesthetized, intubated, ventilated, catheterized, and assigned randomly to a sham group or one of three experimental groups undergoing 720 degrees torsion of the left testis for 8 hours after which it was untwisted in group I and removed in group II. In group III, both testes were removed. Data were collected at baseline (T = 0), 4 hours (T = 4), and 8 hours of torsion (T = 8) and at the ninth hour of the experiment (T = 9). Testicular blood flow was determined by using radiolabeled microspheres. The testes also were examined blindly with routine and electron microscopy.

RESULTS

In group I, testicular blood flow decreased in the affected testis during torsion and increased significantly after detorsion, whereas blood flow to the contralateral testis increased significantly after detorsion. Sham-operated animals showed no histological abnormality in either testis. In all torsion groups, the affected testis showed extensive changes caused by hemorrhagic necrosis. The contralateral testis only showed changes in group I.

CONCLUSION

Unilateral testicular torsion resulted in ipsilateral damage caused by a decrease and subsequent increase in blood flow while in the contralateral testis; damage was the result of a significant increase in blood flow after detorsion.

Correlation of flow probe determinations of common carotid artery blood flow and internal carotid artery blood flow with microsphere determinations of cerebral blood flow in piglets

We investigated whether blood flow determined by a flow probe situated on one common carotid artery provided an accurate estimation of unilateral cerebral blood flow (CBF) in piglets. In eight anesthetized, mechanically ventilated piglets, blood flow determined by an ultrasonic flow probe placed on the right common carotid artery was correlated with CBF determined by microspheres under two experimental conditions: 1) before ligation of the right external carotid artery with both the right external and internal carotid circulations intact [common carotid artery blood flow (CCABF) condition], and 2) after ligation of the right external carotid artery (ipsilateral to the flow probe) with all residual right-sided carotid artery blood flow directed through the right internal carotid artery [internal carotid artery blood flow (ICABF) condition]. The left carotid artery was not manipulated in any way in either protocol. Independent correlations of unilateral CCABF and ICABF with microsphere-determined unilateral CBF were highly significant over a 5-fold range of CBF induced by hypercarbia or hypoxia (r = 0.94 and 0.92, respectively; both p < 0.001). The slope of the correlation of unilateral CCABF versus unilateral CBF was 1.68 +/- 0.19 (SEM), suggesting that CCABF overestimated CBF by 68%. The slope of the correlation of unilateral ICABF versus unilateral CBF did not differ significantly from unity (1.06 +/- 0.15), and the y intercept did not differ significantly from zero [-1.3 +/- 5.2 (SEM) mL]. Consequently, unilateral ICABF determined by flow probe accurately reflected unilateral CBF determined by microspheres under these conditions. Flow probe assessments of CCABF and ICABF in piglets may provide information about dynamic aspects of vascular control in the cerebral circulation that has heretofore been unavailable.

Serial phospholipid analysis in preterm infants: comparison of Exosurf and Survanta

The initial clinical response to synthetic or natural surfactant is different and long-term complications from meta-analysis suggest that bronchopulmonary dysplasia and retinopathy of prematurity may be increased in infants given synthetic surfactant. It is possible that this is due to differences in the phospholipid composition of lung fluid following administration of these surfactants. Infants less than 32 weeks gestation with respiratory distress syndrome (RDS) were randomly assigned to receive either Exosurf, an artificial surfactant, or Survanta, a natural surfactant. Endotracheal or hypopharyngeal aspirates were obtained from these infants and from control infants who had normal lungs. The aspirates were taken prior to and up to 28 days following surfactant administration. The different phospholipids were separated by thin layer chromatography and expressed as a percent of total phospholipid measured. Infants with normal lungs had a higher proportion of phosphatidylcholine than those with RDS prior to treatment. The infants with normal lungs had a greater proportion of phosphatidylinositol in their lung aspirates than both treatment groups at 24 h. Infants in the Survanta group had a higher proportion of phosphatidylglycerol at 48 h than the group with normal lungs. No other differences were found in phospholipid composition up to 28 days. There were no major differences in the phospholipid profile in infants with RDS treated with either Exosurf or Survanta. In conclusion, neither the clinical differences initially seen between infants treated with either Exosurf or Survanta, nor the long-term outcome could be explained by the phospholipid composition of serial samples of lung aspirates.

Cytological changes in endotracheal aspirates associated with chronic lung disease

Endotracheal aspirates taken serially from mechanically ventilated premature infants born at < 28 weeks gestation between March 1992 and August 1993 were studied to determine whether early cytological changes would be a good predictor of lung damage in infants who develop chronic lung disease (CLD). CLD was diagnosed if the infant required supplemental oxygen at 36 weeks corrected gestational age. Fifty-five infants were enrolled in the study, five died and of the 50 infants remaining, 17 (34%) developed CLD. The infants with CLD had a significantly lower gestation (25.5 +/- 1.8 (mean +/- 1 SD) versus 26.2 +/- 0.9 weeks, p < 0.05), significantly more required surfactant (14/17 vs. 16/33, p < 0.05) and were ventilated for a significantly longer period (43.3 +/- 26.6 vs. 19.3 +/- 12.8 days, p < 0.0001). Endotracheal aspirate cytology showed that infants with CLD had significantly more degenerated columnar epithelial cells on day 3 (p = 0.001), and more neutrophils on day 10 (p = 0.007). Though not predictive of CLD, cytological changes consistent with bronchial epithelial and pulmonary damage followed by an inflammatory response were found in the tracheal aspirates of a group of infants clinically diagnosed with CLD.

Retinopathy of prematurity in infants <29 weeks' gestation at birth in New South Wales from 1986-92

OBJECTIVE

To study the effect of increased survival of infants <29 weeks' gestation on the incidence and severity of retinopathy of prematurity (ROP).

METHODOLOGY

Review of prospective records from 1986 to 1992 kept in the New South Wales (NSW) NICUS database on infants admitted to the neonatal intensive care units (NICU) in NSW. The survival rate and the incidence and severity of ROP on all infants <29 weeks' gestation admitted to the NICUs in NSW from 1 July 1986 to 31 December 1987 were compared to a similar group of infants admitted from 1 January 1992 to 31 December 1992.

RESULTS

There was a significant difference in the survival rate of infants admitted between the two periods (235 of 376, 62.5% survival vs 255 of 336, 75.9% survival, respectively, P<0.0001). The odds ratio for survival adjusted for gestational age in the second period was 1.76 [1.24, 2.48 (95% confidence interval), P<0.002]. There was a slight increase in ROP in the second period (79 of 172 examined, 45.9% ROP vs 133 of 238 examined, 55.8% ROP, respectively). There was a rise in the number of infants with Stage 3 ROP in the second time period (14 of 172 examined, 8.1% ROP vs 41 of 238 examined, 17.2% ROP, respectively). However, fewer infants had detached retinas or > or = Stage 4 ROP in the second group [7 of 172, (4.1 %) vs 3 of 238, (1.3%), respectively]. This may be a reflection of the increase in the use of cryo- or laser therapy for Stage 3 ROP with 'plus' disease [2 of 172 examined, (1.2%) vs 18 of 238 examined, (7.6%), respectively].

CONCLUSIONS

With the increase in survival of the very preterm infant in recent years, there has been an increase in severe ROP (> or = Stage 3) in NSW. Despite the increased survival of the highest at-risk group (24- to 26-week gestation infants), there have been fewer cases of retinal detachment. There was also a rise in the number of infants receiving cryo- or laser therapy intervention.

Chronic oxygen dependency in infants born at 24-32 weeks' gestation: the role of antenatal and neonatal factors

OBJECTIVES

To study the incidence of chronic oxygen dependency (COD) among ventilated survivors born at 24-32 weeks gestation from 1986 to 1994 and to identify antenatal and neonatal factors that may have changed with time; and to identify antenatal and neonatal factors that could contribute to the development of COD in infants born at 24-32 weeks gestation using a case control model.

METHODOLOGY

Infants born at 24-32 weeks gestation in one tertiary referral centre between 1986 and 1994 and admitted to the neonatal intensive care unit for respiratory support were studied. Data accumulated prospectively since 1986 in survivors of ventilation were analyzed to identify antenatal and neonatal factors that could have changed with time. The cohort of infants who developed COD were matched for gestation and time of birth with a control group of infants who did not have COD. Significant factors that could have contributed to the development of COD were identified using forward logistic regression analysis.

RESULTS

The number of mothers admitted for threatened premature labour (TPL), and pregnancy induced hypertension decreased with time while the use of antenatal steroids and maternal antibiotics increased. More infants were delivered by Caesarean section during the later years. There was an increase in neonatal septicaemia with time while there were decreases in hyaline membrane disease, pneumothorax, pulmonary interstitial emphysema, use of high peak inspiratory pressure (PIP) and high inspired oxygen. The incidence of COD decreased. The case controlled study revealed a significant positive association between COD and male gender, birthweight less than the 10th percentile for gestation, PIP over 30 cm H2O, septicaemia and significant patent ductus arteriosus (PDA) requiring indomethacin. There was a negative association with TPL.

CONCLUSIONS

Further decrease in COD can be achieved only if septicaemia, PDA and the use of high PIP can be avoided. The most effective way of reducing the incidence of COD is by reducing the incidence of prematurity.

Mutations in the chloride channel gene, CLCNKB, cause Bartter's syndrome type III

Analysis of patients with inherited hypokalaemic alkalosis resulting from salt-wasting has proved fertile ground for identification of essential elements of renal salt homeostasis and blood-pressure regulation. We now demonstrate linkage of this phenotype to a segment of chromosome 1 containing the gene encoding a renal chloride channel, CLCNKB. Examination of this gene reveals loss-of-function mutations that impair renal chloride reabsorption in the thick ascending limb of Henle's loop. Mutations in seventeen kindreds have been identified, and they include large deletions and nonsense and missense mutations. Some of the deletions are shown to have arisen by unequal crossing over between CLCNKB and the nearby related gene, CLCNKA. Patients who harbour CLCNKB mutations are characterized by hypokalaemic alkalosis with salt-wasting, low blood pressure, normal magnesium and hyper- or normocalciuria; they define a distinct subset of patients with Bartter's syndrome in whom nephrocalcinosis is absent. These findings demonstrate the critical role of CLCNKB in renal salt reabsorption and blood-pressure homeostasis, and demonstrate the potential role of specific CLCNKB antagonists as diuretic antihypertensive agents.

Retinopathy of prematurity in infants less than 29 weeks' gestation: 3 1/2 years pre- and postsurfactant

OBJECTIVE

To determine the effects of surfactant on retinopathy of prematurity (ROP).

DESIGN

We compared infants for 3 1/2 years both before and after the introduction of surfactant in our neonatal intensive care unit (NICU) using prospectively collected data. Exogenous surfactant (Exosurf) was introduced into our NICU on July 1, 1991.

METHODS

We compared the incidence and severity of ROP in two groups of infants born at less than 29 weeks' gestation who required cryo- or laser therapy. Premature infants born during the first 3 1/2 years following the introduction of surfactant were compared with those born during the 3 1/2-year period prior to its introduction. The infants were examined by one ophthalmologist (J.K.) and classified according to the International Classification of ROP.

RESULTS

A total of 124 infants born presurfactant and 152 infants born postsurfactant were examined for the presence of ROP. No significant difference between the two groups regarding any stage of ROP or the necessity for treatment was found. In infants of less than 27 weeks' gestation, a significant reduction in the number requiring cryo- or laser therapy was noted (12 of 48 examined [25.0%] vs 6 of 62 examined [9.7%], respectively; P < 0.05). This decreased need for treatment, however, was found in infants without hyaline membrane disease who did not receive surfactant.

CONCLUSION

Exosurf has had no significant impact on the incidence or severity of ROP. Due to its effect on improved survival rates, the surfactant produces a larger proportion of infants at risk of developing ROP. Other changes in NICU protocol may be causing a reduction in the incidence of severe ROP.

Bacterial colonization of indwelling vascular catheters in newborn infants

OBJECTIVE

To determine the incidence of bacterial colonization of intravascular catheters, to compare the incidence of colonization of intra-arterial (IA), intravenous (IV) and central venous catheters (CVC), and to determine the association, if any, between catheter withdrawal and bacterial sepsis.

METHODOLOGY

A prospective observational study was carried out at the neonatal intensive care unit of a university-affiliated regional referral centre. A total of 155 catheters (45 IA, 54 IV and 56 CVC) were obtained from 96 infants admitted to the unit and the distal 0.75 cm studied under the scanning electron microscope. The adjoining 0.75 cm was cultured for bacteria.

RESULTS

Scanning electron microscopy revealed that 46% of catheters had bacteria on the internal surface and 13% had bacteria on the outer surface. Greater numbers of CVC were colonized with bacteria compared to IA and IV catheters (P < 0.01). Bacterial colonization of intravascular catheters was not significantly associated with the duration the catheter remained in situ or local reaction at the site of entry of the catheter. Colonization of the external surface of the catheter was significantly associated with bacterial septicaemia (P = 0.0466). Eighty-three per cent of 155 catheters studied had coagulum on the inner or outer surface. Only 53% of these were colonized with bacteria. Bacterial colonization occurred in the absence of a coagulum in only three instances. Catheter withdrawal was not associated with bacterial sepsis. Lack of coagulum on the internal surface of the catheter was strongly associated with septicaemia during the 7 days after catheter withdrawal.

CONCLUSIONS

Although significant numbers of intravascular catheters were colonized with bacteria, only colonization with the external surface was associated with catheter-related sepsis.

Dysosteosclerosis

A 5 1/2 year old boy presented with delayed development and loss of vision. A skeletal survey showed osteosclerosis consistent with dysosteosclerosis. Some unusual features of dysosteosclerosis are discussed.

Effect of nimodipine on systemic, renal, and cerebral haemodynamics after a mild hypoxic-ischaemic insult in newborn piglets

Because many Ca2+ channel blocking agents are known to cause adverse systemic effects, in this study we tested the haemodynamic side effects of nimodipine with and without a mild hypoxic-ischaemic (HI) insult in a newborn piglet model. Fifteen min after completing a brief period of asphyxia we gave i.v. nimodipine as 5 micrograms kg-1 bolus followed by 0.1 microgram kg-1 min-1 continuous infusion for 105 min in six piglets, while the same treatment was repeated in five animals without preceding HI insult. At third group of six served as sham operated controls. In the HI insult group by 105 min of nimodipine infusion the mean BP dropped by 30% and the cardiac output dropped by 23% of respective baseline. In this group, the renal blood flow dropped between 65% and 77% of baseline and regional cerebral blood flow dropped between 28% and 55% of respective baseline by 45 min and 105 min of nimodipine fashion. In the group with no prior HI insult, 105 min of nimodipine infusion caused no significant changes in these variables. Despite nimodipine infusion, HI insult caused a significant increase in the mean brain water content compared to the two control groups: 89 +/- 3.2% compared to 82.7 +/- 0.5% in the nimodipine control group, and 83.7 +/- 1.7% in the sham group (P < 0.0001). We conclude that while nimodipine therapy without prior asphyxial insult does not cause significant adverse haemodynamic effects, its infusion after even a mild HI insult could cause reduction in renal blood flow and moderate reduction in regional cerebral blood flow, BP, and cardiac output, suggesting a differential effect. A 15 min lag between HI insult and nimodipine therapy may be too long to prevent cerebral oedema.

Renal actions of endothelin-1 in newborn piglets: dose-effect relation and the effects of receptor antagonist (BQ-123) and cyclooxygenase inhibitor (indomethacin)

Although the effects of endothelin-1 (ET-1) on intact or perfused adult kidney are well understood, its effects in the fetus and the newborn have not been well studied. We examined the effects of infusions of 25, 50, and 100 ng/kg of ET-1 per minute on mean blood pressure (MBP), cardiac index (CI), renal blood flow (RBF), glomerular filtration rate (GFR), and urine volume (UV) in 7- to 10-day-old piglets (n = 24). In addition, the effects of pretreatment with a receptor antagonist (BQ-123) and with a cyclooxygenase inhibitor (indomethacin) were studied in 12 separate piglets. ET-1 produced a dose- and level-dependent decrease in CI (60%), RBF (50% to 75%), GFR (66% to 80%) and MBP 15% to 17%. These changes returned to 75% to 80% of baseline 60 minutes after discontinuation of ET-1. Low-dose infusion (25 ng/kg) did not result in any changes in systemic or renal hemodynamics. Plasma half-life of ET-1 in piglets was 2.1 +/- 0.4 minutes. Pretreatment with the specific ETA receptor antagonist BQ-123 completely blocked the ET-1-induced systemic and renal hemodynamic changes. Indomethacin blocked the ET-1-induced rise in MBP but failed to block any renal changes. In fact, indomethacin accentuated the changes induced by ET-1, especially the changes in RBF, RVR, and GFR. Studies of receptor binding in the renal cortex and medulla showed that, in the cortex, the Ki value for ET-1 was 6.32 +/- 1.57, and for ET-3 it was 20.05 +/- 4.38 (p < 0.05); in the medulla, the Ki values were similar for both ET-1 and ET-3. These results indicate that in piglets the renal vascular bed is highly sensitive to ET-1, and its effects are predominantly mediated through ETA receptors.

Case report: neonatal platyspondylic dwarfism--a new form

A new type of neonatal bone dysplasia is reported. Unusual radiographic abnormalities (platyspondyly with unique shape of the vertebral bodies, shortening of the long tubular bones without signs of rickets or metaphyseal dysplasia, marked shortening of well-ossified short tubular bones, schneckenbecken-like pelvis with tri-radiate acetabulum, pseudoepiphysis of the right ulna, unusual shape of calcaneus and periarticular calcifications) allow designation of this disorder as a new form of neonatal dwarfism.

Technetium-99m-labeled monoclonal antibodies: influence of technetium-99m binding sites

A number of 99mTc-labeled monoclonal antibodies (Mabs) are being evaluated for diagnostic applications. Preparations are carried out using both direct and indirect (bifunctional chelating agent, BFCA) labeling procedures in which nonspecific 99mTc binding has been postulated.

METHODS

By using the ascorbic acid (AA) reduction mediated direct labeling procedure and diaminotetrathiol (N2S4) as a BFCA method, we examined the role of specific binding sites and aliphatic E amino groups of lysine as nonspecific binding sites for 99mTc.

RESULTS

Labeling yields for the direct and N2S4 "regular" preparations averaged 73% +/- 2.8% and 91% +/- 2%, for the "specific" preparations, 60% +/- 3.5% and 75% +/- 2% and for the "nonspecific" preparations 13% +/- 1.0% and 16% +/- 1% respectively. All preparations were evaluated in tumor-bearing mice. The control and specific preparations permitted excellent scintigraphic visualization of tumors; the percentages of specific preparations in the tumors being 2.1% +/- 0.5% and 3.1% +/- 0.4%, respectively. With nonspecific preparations, tumors were not visualized and the percentages of administered radioactivity per gram of tumor were only 0.9% +/- 0.2% and 0.9% +/- 0.3%, respectively.

CONCLUSIONS

In these 99mTc labeling procedures, the amino group-mediated nonspecific binding of 99mTc to Mabs can be as high as 16% and contributes to increased liver uptake and decreased tumor uptake of radioactivity.

Body electrolytes in bronchopulmonary dysplasia and the effects of diuretic therapy

Body electrolytes and their regulatory hormones were studied in preterm infants who suffered from bronchopulmonary dysplasia under two groups: those who were not treated with diuretics (Group II), and those who were treated with diuretics (Group III). The values were compared with a group of matched healthy controls (Group I). Lower serum Na levels, a need of higher Na intake, and higher urinary Na concentrations and urinary specific gravity were found in Group II infants. FeNa was normal and the urinary flow rate was lower than the controls. These data suggest an inability of these infants to dilute urine. Group III infants who were treated with diuretics showed higher serum Na levels and lower urinary specific gravity than Group II infants. These values, as well as water and Na intake/output ratios, were all similar to the control values. Serum aldosterone level was highest in Group II but did not reach significance. Intracellular K concentration was not different between the groups indicating an optimum total body K balance. A significant negative correlation between serum Na and aldosterone levels was found in Group II infants, which was not noted in the controls. Significant correlations were also found between FeNa and plasma aldosterone level in the BPD groups, unlike the controls. The control group of infants showed significant positive correlation between Na balance and serum Na levels. Our results suggest that inability to dilute urine appropriately might be the reason for the BPD patients to retain body water. Water restriction and diuretic therapy therefore are reasonable therapeutic approaches in such cases.

Retinopathy of prematurity in infants less than 29 weeks' gestation at birth

From January 1986 to December 1991 we examined the eyes of 206 infants born at Westmead Hospital, Neonatal Intensive Care Unit who were less than 29 weeks' gestation at birth to determine the incidence of retinopathy of prematurity. Eighty-five infants (41.3%) had no retinopathy of prematurity (ROP) in either eye, 82 infants had stages 1 or 2 ROP (39.8%), 29 had stage 3 ROP (14.1%) and 11 had stage 4 ROP (5.3%). Of these, cryotherapy was performed in 18; six now have bilateral retinal detachment and are blind. The more severe stages of ROP were significantly associated with an increase in the number of days of oxygen supplementation, an increase in the number of days of mechanical ventilation and the presence of patent ductus arteriosus. Infants receiving steroids for mechanical ventilator dependence had a significantly greater chance of requiring cryotherapy (11 or 22 receiving steroids versus seven of 43 without steroids; P < 0.01).

Structural perturbations of monoclonal antibodies following radiolabelling: in vitro evaluation of different techniques

Antibodies are labelled routinely with direct labelling techniques in which some of the native disulphide groups are reduced to sulphydryls. Using polyacrylamide gel electrophoresis (PAGE) as an analytical tool and human polyclonal IgG (HIgG) labelled with 99Tcm by the ascorbic acid (AA), stannous chloride (SnCl2) and 2-mercaptoethanol (2-ME) techniques, we have quantitatively determined any fragmentation of the protein and the radioactivity associated with fragments. HIgG labelled with 99Tcm by two bifunctional chelating agents provided the vital comparison. The results indicated that in the bifunctional chelating agent (BFCA) methods 65 and 61% of the activity was associated with protein with an apparent molecular weight of 150,000 D. The corresponding numbers for the AA, SnCl2 and 2-ME methods were 46.4, 21 and 3.9%. With 2-ME, 96% of the activity was associated with low molecular weight fragments. Although monoclonal antibody fragmentation may not affect immunoreactivity of the protein, it may influence biodistribution.

Surfactant replacement therapy in neonates less than 32 weeks gestation: effect on neonatal intensive care resource utilization

The effect of synthetic surfactant (Exosurf) replacement on complications from hyaline membrane disease (HMD) in infants < 32 weeks gestation and their resource utilization within a neonatal intensive care unit was studied in 1991-92. A control group was selected from infants admitted to the same unit during the preceding 3 years when Exosurf was not available. The infants were controlled for gestation, weight and severity of HMD. Infants given Exosurf had a significant reduction in the incidence of pulmonary interstitial emphysema (PIE), and a marginal decrease in the incidence of pneumothorax. They required fewer days on the ventilator and consumed less of the scarce financial resources. There was no difference in the mortality rate among the two groups. The changes seen were more evident among those infants between 30 and 31 weeks gestation, compared to those < 28 weeks.