Genetic mapping of the cleidocranial dysplasia (CCD) locus on chromosome band 6p21 to include a microdeletion

Cleidocranial dysplasia (CCD) is a generalized skeletal dysplasia with autosomal dominant inheritance. Recently, the CCD disease locus was localized to 23 [Mundlos et al., 1995] and 17 cM regions [Feldman et al., 1995], of chromosome band 6p21 by linkage studies of seven affected families. Of note, the 23 cM region contained a microdeletion detected in one family at D6S459, an interval that was excluded in the 17 cM overlapping region. Here, linkage of CCD to 6p21 was independently confirmed with a maximal two-point LOD score of Z = 5.12 with marker D6S452 at theta = 0.00. Recombinant events in two affected individuals defined a CCD region of 7 cM from D6S465 to D6S282, which overlapped with the CCD region containing the microdeletion but did not overlap with the 17 cM critical region from D6S282 to D6S291. These results suggest the refined localization of the CCD region to 6 cM spanning markers D6S438 to D6S282, thereby reviving the possibility that the CCD gene lies within the microdeletion at D6S459.

A rapid, direct test for zidovudine susceptibility in clinical isolates of human immunodeficiency virus type 1 (HIV-1) from infected children

BACKGROUND

Existing phenotypic tests of antiretroviral susceptibility in clinical isolates of human immunodeficiency virus (HIV) are expensive and slow, and require passage of virus in cell culture with the possible consequence of selecting variants.

OBJECTIVES

We sought to develop a rapid 14-day assay for zidovudine susceptibility of cell-associated HIV performed directly in patient blood samples.

STUDY DESIGN

Twenty-three tests were performed prospectively in 21 children, and the results were compared with those of the AIDS Clinical Trials Group/Department of Defense consensus drug susceptibility assay (DSA) as well as certain clinical parameters.

RESULTS

Five strains from ZDV-naive children were sensitive by the rapid test. Three were tested by DSA, and all were sensitive. Six strains from children who had received >/=24 months of ZDV were resistant by the rapid assay. Four of these strains were tested by the DSA, and all were shown resistant. The viral strains from children who received <24 months of therapy or who had switched from ZDV to other antiviral therapy exhibited variable sensitivity by both tests. Changes in CD4 cells in the subsequent 6 months, as well as weight gain during this time were both correlated to the results of the rapid test. The syncytium-inducing capacity of the virus strains was analyzed similarly.

CONCLUSIONS

The rapid intracellular virus susceptibility assay is a test of drug sensitivity performed on HIV growing in cells obtained directly from an infected patient. The test has a two-week turn-around time and, in this preliminary report, gives results which correlate with both time on zidovudine and also subsequent CD4 cell changes.

The developmental increase in ACh current densities on rat sympathetic neurons correlates with changes in nicotinic ACh receptor alpha-subunit gene expression and occurs independent of innervation

Determining factors that control the expression of neurotransmitter receptors and the mechanisms by which these factors operate is essential to understand how synapses form during development and how receptor numbers change in the adult. In this study, we have investigated one such factor, the influence of innervation, on the developmental expression of nicotinic ACh receptors (nAChRs) on neonatal rat sympathetic neurons, both in terms of ACh current densities, and in terms of mRNA levels for the transcripts that encode these receptors. To date, nine genes have been cloned that encode neuronal nAChRs subunits in mammals. We demonstrate that mRNA encoding five nAChR subunits, alpha 3, alpha 5, alpha 7, beta 2, and beta 4, are present in neonatal rat sympathetic neurons. We show that mRNA levels for alpha 3 and alpha 7 subunits increase by more than threefold over the first 2 postnatal weeks, a period when most synapses are forming on the neurons; however, we observed no significant change in mRNA levels for alpha 5, beta 2, or beta 4. Using whole-cell voltage-clamp techniques, we show that the increase in alpha-subunit mRNA correlates with increases in ACh current densities, which double over the same period. To investigate the role of innervation, we cut the preganglionic nerve at birth and measured subunit mRNA levels and ACh current densities in denervated neurons 1-2 weeks later. Our results indicate that the preganglionic nerve differentially affects the mRNA level for the five nAChR transcripts, yet it has little influence on the developmental increase in ACh current densities.

Cardiac surgery in the very elderly

OBJECTIVE

To determine the results of cardiac surgery in the very elderly.

DESIGN AND SUBJECTS

A retrospective study of 56 very elderly patients (mean age 82 years, range 79-89 years) undergoing open heart surgery between 1988 and 1991. Thirty-three patients had coronary artery bypass grafting, 12 had valve replacement alone and 11 had valve replacement with an associated procedure.

SETTING

St Francis Xavier Cabrini Hospital, Melbourne--a large private hospital.

RESULTS

There were four in-hospital deaths (7%). The one-year actuarial survival rate was 88%. Of the 49 survivors, 92% were in New York Heart Association (NYHA) Class III or IV before operation, whereas 96% were in NYHA Class I or II a mean of 15 months after operation.

CONCLUSION

In very elderly patients with medically refractory cardiac symptoms, cardiac surgery has a tolerable mortality and provides excellent relief of symptoms.

Clinicopathological correlates of cardiac myxomas: a 30-year experience

Between 1961 and 1991, 23 patients (eight men and 15 women, with a mean age of 50 (range 25-72) years) with cardiac myxomas were managed at the Alfred Hospital, Prahran, Victoria, Australia. Symptoms of mitral valve obstruction were present in 13 patients and of systemic embolism in nine. In the patients, 21 myxomas were confined to the left atrium. In the other two patients, one myxoma was confined to the right atrium and the other was a dumb-bell-shaped biatrial myxoma. Most tumours were diagnosed with echocardiography. Removal was achieved via a median sternotomy and by entering the involved chamber. Those myxomas presenting with systemic embolism were always soft and friable, whereas those with obstructive symptoms were large and of variable consistency. There was one operative death early in the series. The 22 surviving patients have been assessed as functional class I of the New York Heart Association at follow-up, ranging from 2 months to 23 years (mean 9 years). There were no episodes of tumour recurrence. Excellent short, intermediate and long-term results can be achieved by excision of cardiac myxomas.

Extrinsic factors influence the expression of voltage-gated K currents on neonatal rat sympathetic neurons

Voltage-gated potassium (K) currents are important in controlling a neuron's excitability. We have shown previously (McFarlane and Cooper, 1992) that neonatal superior cervical ganglia (SCG) neurons express three voltage-gated K currents: a noninactivating delayed-rectifier type current (IK), a rapidly inactivating A-current (IAf), and a slowly inactivating A-current (IAs). When grown in culture for 4 weeks without other cell types, SCG neurons lose their expression of IAf and IAs, suggesting that an extrinsic factor(s) is involved in controlling the expression of these currents. In vivo, SCG neurons are surrounded by non-neuronal cells. Therefore, in this study we investigated whether the ganglionic non-neuronal cells provide a factor required for A-current expression. We show that postnatal day 1 (P1) SCG neurons continue to express IAf and IAs when cocultured with their ganglionic non-neuronal cells. Medium conditioned by ganglionic non-neuronal cells mimics the non-neuronal cell influence on IAf and IAs expression, suggesting that the effects of non-neuronal cells are mediated by way of a secreted factor. Ciliary neurotrophic factor, a factor present in peripheral non-neuronal cells, had similar effects to those of ganglionic cell-conditioned medium. Moreover, we find that the dependence of IAf on a non-neuronal cell factor is developmentally regulated; P14 neurons grown in culture without other cell types continue to express IAf. However, IAs on P14 neurons maintains its dependence on a factor from non-neuronal cells. Finally, in addition to extrinsic control of voltage-gated K currents, we suggest that SCG neurons use intrinsic mechanisms to coordinate their expression of IAf, IAs, and IK such that changes in one K current are compensated for by reciprocal changes in one or more of the other K currents.

NGF induces neonatal rat sensory neurons to extend dendrites in culture after removal of satellite cells

Vertebrate sensory neurons have a pseudo-unipolar morphology; their somata are covered by satellite cells and lack dendrites or synaptic contacts. However, when neonatal rat sensory neurons from the nodose ganglia develop in culture in absence of satellite cells and with NGF, they form synapses among themselves. In this study, we investigated whether neonatal rat nodose neurons express dendrites under the same culture conditions. We show by Lucifer yellow injection that nodose neurons remain typically unipolar when cocultured with their ganglionic satellite cells. However, when these neurons are cultured without satellite cells, virtually all neurons acquire a multipolar morphology. Moreover, when NGF is added to satellite cell-free cultures, several neurons extend dendrites; these processes stain positively for microtubule-associated protein-2. NGF induces a 17-fold increase in dendritic outgrowth after 3 weeks but has little effect on axon number. In addition, we find that the ability of nodose neurons to extend dendrites is developmentally regulated. Furthermore, in a combined morphological and electrophysiological study, using whole-cell voltage-clamp technique with Lucifer yellow in the recording solution, we demonstrate a positive correlation between the extent of dendritic outgrowth and the density of ACh currents, suggesting that these dendrites have ACh receptors. Our results indicate that neonatal rat nodose neurons are capable of extending dendrites and that extrinsic factors can induce or suppress their extension. In addition, the results suggest that these dendrites may act as principal post-synaptic structures for synapse formation that occurs in these cultures.

The expression of nicotinic acetylcholine receptors by PC12 cells treated with NGF

The expression of neuronal nicotinic ACh receptors (nAChRs) and the subunits that compose these receptors by PC12 cells exposed to NGF has been studied. The analysis of total RNA reveals that the neuronal nAChR subunits alpha 3, alpha S, beta 2, beta 3, and beta 4, but not alpha 2 and alpha 4, are expressed in our PC12 cells. Within 48 hr of adding NGF to cultures, the RNA corresponding to alpha 3, alpha 5, beta 3, and beta 4 is decreased, but the beta 2 RNA increases for up to 6 d after NGF treatment. To determine the influence of NGF treatment on subunit protein expression, subunit-specific antisera were prepared. Immunocytochemistry detected antigen for alpha 3, alpha 5, beta 2, beta 3, and beta 4 (but not alpha 2 and alpha 4) in both NGF-treated and nontreated PC12 cells. The expression of nAChR subunit proteins, as measured by direct binding of antibodies to PC12 cells, does not change subsequent to 6 d of treatment with NGF. Whole-cell recording of PC12 cells shows that both the individual cell current density and response to the agonist cytisine were not altered after 5-7 d in NGF. However, the number of cells exhibiting detectable ACh-induced currents doubled. These results indicate that NGF increases the number of PC12 cells expressing ACh-sensitive nAChR currents but the activation is not the result of altering the amounts of individual nAChR subunit proteins. These data, taken together with the decrease in most nAChR subunit RNAs (except beta 2), suggest that NGF regulation of nAChRs may be through a posttranscriptional mechanism.

Effects of ganglionic satellite cells and NGF on the expression of nicotinic acetylcholine currents by rat sensory neurons

1. We have investigated two factors that affect the expression of nicotinic acetylcholine (ACh) currents on neonatal rat sensory neurons: an influence derived from ganglionic satellite cells, and nerve growth factor (NGF). 2. With the use of whole-cell patch-clamp techniques on rat nodose neurons, we have measured the proportion of neurons sensitive to ACh and have quantified their ACh current densities. The majority (60%) of nodose neurons from neonatal animals do not express nicotinic acetylcholine receptors (nAChRs); the remaining 40% had ACh current densities that ranged from 0.4 to 93 pA/pF. Furthermore, neither the proportion nor the ACh current densities change over the first two postnatal weeks in vivo. 3. The expression of ACh currents by these neurons in vivo is controlled, in part, by an influence from the ganglionic satellite cells: culturing neurons in the absence of other cell types results in an increase in the proportion of ACh-sensitive neurons, whereas coculturing neurons with their satellite cells maintains functional nAChR expression in its in vivo state. Furthermore, satellite cells are not required continually, as a brief exposure to this influence, either in vivo or in culture, is sufficient to exert its effect on functional nAChR expression. 4. On removal of this satellite cell influence, the neurons respond to NGF treatment by increasing their ACh current densities: the median ACh current density for neurons grown for 2-3 wk with NGF was 32.5 pA/pF, whereas, the median ACh current density for neurons cultured without NGF for the same time was 4.5 pA/pF.(ABSTRACT TRUNCATED AT 250 WORDS)

Postnatal development of voltage-gated K currents on rat sympathetic neurons

1. We have investigated the developmental expression of three voltage-gated K currents on neonatal rat superior cervical ganglion (SCG) neurons in vivo and in culture: a rapidly inactivating current (IAf), a slowly inactivating current (IAs), and a noninactivating current (IK). 2. On postnatal day 1 neurons (P1), mean peak IAs is 67 +/- 4 (SE) pA/pF, peak IAf is 27 +/- 3 pA/pF, and IK is 14 +/- 3 pA/pF. Over the next wk, there is a switch in the expression of these currents: IAs drops by 40%, whereas IAf increases by greater than 100%; there is no change in IK. On P14 neurons, IAs is 38 +/- 2 pA/pF, IAf is 64 +/- 5 pA/pF, and IK is 12 +/- 1 pA/pF. 3. The change in expression of K currents on SCG neurons over the first 2 postnatal wk is unaffected by preganglionic innervation or by innervation of the targets. 4. To learn more about the factors that affect K current expression on these neurons, we grew SCG neurons in culture without other cell types for various times, and we measured the expression of IAf, IAs, and IK. In culture, the currents remained at their P1 levels for the first 4-7 days. Thereafter, both IAs and IAf decreased to low levels over a period of 2-3 wk. These results suggest that an epigenetic factor(s) is necessary for the expression of IAf and IAf in vivo and that this factor is missing in culture. 5. When IAs and IAf decreased on neurons in culture, we observed a compensatory increase in IK. After 4 wk in culture, IK is fourfold greater than on neurons in vivo. This result suggests that these neurons have intrinsic mechanisms that coordinate the expression of different voltage-gated K currents.

Atrial natriuretic peptide does not alter cerebrospinal fluid formation in sheep

Because the choroid plexus has been shown to have a high density of atrial natriuretic peptide (ANP) binding sites, we investigated the effect of intracerebroventricular and intravenous administrations of ANP on cerebrospinal fluid (CSF) formation. CSF formation rate was measured in conscious sheep with a dye-dilution method using blue dextran 2000 as an indicator substance. During the experiment animals were partially restrained in a sling, and their ventricular systems were perfused with artificial CSF containing the indicator substance. ANP (alpha-human ANP) administered centrally at rates of 0.015-15 ng/min, resulting in CSF ANP concentrations ranging from physiological to pharmacological CSF hormone levels, was found not to influence CSF formation. Similarly, intravenous administration of ANP at a rate of 10 ng.kg-1.min-1 did not affect CSF formation, i.e., decreases in CSF formation rate in all experiments involving ANP administration were not significantly different from those observed in time control experiments. Our results suggest that ANP does not significantly affect CSF production in sheep. It is possible that the lack of effect of ANP on CSF formation is associated with the predominance in the choroid plexus of clearance receptors over biologically active receptors.

The effect of haemorrhage on erythropoietin concentration in the mature ovine fetus

This study examines the response in plasma erythropoietin values to haemorrhage of 20% of the estimated blood volume in chronically cannulated ovine fetuses, of gestational ages 128-144 days. Blood samples were collected at 0, 2, 4, 6 and 24h with respect to the haemorrhage. In 5 control experiments there was no significant change in plasma erythropoietin concentration, across this time period, values being 6.1 +/- 2.3 and 6.4 +/- 2.4 mU/ml at 0 and 24h respectively. Values are mean +/- SEM. Haemorrhage reduced the haematocrit and haemoglobin values, significantly, to 83 +/- 6% and 85 +/- 4% (n = 5) of the initial value, respectively, but did not cause a statistically significant increase in plasma erythropoietin concentrations (7.2 +/- 2.4 and 20.7 +/- 8.2 mU/ml; P = 0.131). A larger degree of haemorrhage, in four fetuses reduced the haematocrit to 64 +/- 2.8% of initial, over 24-54h and increased erythropoietin values very significantly (from 11.9 +/- 3.6 to 91 +/- 8.3 mU/ml; P = 0.001).

Angiographic assessment of graft patency after coronary endarterectomy

Fifty-one consecutive patients underwent 68 manual core endarterectomies between April 1985 and May 1987. There were 42 men and nine women, mean age 60 years (range 39 to 81). All patients underwent coronary bypass grafting alone. There were no reoperations. There was one operative death (2%). Forty patients consented to early (mean 19 days) and 27 to late (mean 19 months) repeat angiography. At the early restudy 47 of 52 (90%) grafts to endarterectomized vessels were patent. This rate fell to 27 of 42 (64%) at late restudy. There was considerable variation in the angiographic appearance of the endarterectomized vessels, ranging from a large caliber, smooth walled vessel to an attenuated vessel with irregular walls. In general, there was a tendency toward "shrinkage" of these vessels by the late restudy, suggesting fibrosis in the walls. We conclude that, although endarterectomy can be done on most atheromatous vessels with excellent early graft patency, these vessels tend to show an accelerated deterioration with time, resulting in a low late patency rate. We suggest that the procedure be reserved for vessels that are truly inoperable by other means and only for vessels that supply a coronary bed of at least moderate size.

Frankincense and Myrrh as Remedies in Children

Two cases of therapy with frankincense and myrrh in children are presented. The long history of this unusual treatment is outlined, demonstrating that for several millenia such agents have been employed in a number of medical contexts, as well as in the perfume and incense industries. Myrrh has found recent pharmacological application in the reduction of cholesterol and triglycerides, as predicted by several traditional therapies.

Kinetics and voltage dependence of A-type currents on neonatal rat sensory neurons

1. We have characterized three voltage-gated potassium currents on neonatal rat nodose neurons: a rapidly inactivating current (IAf), a slowly inactivating current (IAs), and a noninactivating current (IK). 2. Most neurons expressed all three currents. However, we found that a significant number of neurons had only one of the two A-currents. 3. IAf activates rapidly (tau = 1.0-1.5 ms at -10 mV) and inactivates in 10-30 ms. The activation and steady-state inactivation curves were fit with Boltzmann distributions of V' = -21, k = 12 mV and V' = -73, k = -8 mV, respectively. 4. IAs activates more slowly than IAf (tau = 5.4-9.2 ms at -10 mV) and inactivates with two components (150-300 ms; 1-3 s). The activation and inactivation curves are shifted approximately 20 mV more positive than those of IAf, with Boltzmann coefficients of V' = -2, k = 14 mV and V' = -51, k = -14 mV, respectively. 5. Of the three, IK activates most slowly (tau = 29.4-38.3 ms at -10 mV) and at more positive potentials than IAf or IAs (V' = 16, k = 12 mV). IK does not inactivate over tens of seconds. 6. In addition, we have identified the single channels that underlie IAf and IAs. These two channels, Af and As, have the same single-channel conductance, 22 pS, but different inactivation kinetics. 7. Furthermore, we show that there is an inverse relationship between the appearance of A-currents (IAf and IAs) and the appearance of IK, suggesting that these neurons coordinate the expression of these currents in their membranes.

Anaesthesia and the child with HIV infection

The frequency of AIDS in the paediatric population is growing rapidly and is expected to get worse. The anaesthetist will participate in the care of these children in the operating room and the intensive care unit with increasing frequency and must therefore have an understanding of the many manifestations of this syndrome. Children become infected with HIV by transplacental transmission from mother to fetus in over 80% of cases. Early diagnosis in infants can be very difficult. Clinical manifestations of HIV infection in children result from damage to almost every organ system. Considerations for the anaesthetist include: the effects of medications, cardiovascular dysfunction, pulmonary disease, altered metabolism, equipment preparation, choice of anaesthetic, modes of viral transmission and psycho-social issues.

Pentameric structure and subunit stoichiometry of a neuronal nicotinic acetylcholine receptor

Neuronal nicotinic acetylcholine receptors are members of a gene family of ligand-gated transmitter receptors that includes muscle nicotinic receptors, GABAA receptors and glycine receptors. Several lines of evidence indicate that neuronal nicotinic receptors can be made up of only two subunits, an alpha (alpha) subunit which binds ligand, and a non-alpha (n alpha) or beta (beta) subunit. The stoichiometry of each subunit in the functional receptor has been difficult to assess, however. Estimates of the molecular weight of neuronal nicotonic receptor macromolecules suggest that these receptors contain at least four subunits but probably not more than five. We have examined the subunit stoichiometry of the chick neuronal alpha 4/n alpha 1 receptor by first using site-directed mutagenesis to create subunits that confer different single channel properties on the receptor. Co-injection with wild-type and mutant subunits led to the appearance of receptors with wild-type, mutant and hybrid conductances. From the number of hybrid conductances, we could deduce the number of each subunit in the functional receptor.