Developmental expression of the high affinity choline transporter in cholinergic sympathetic neurons.

Choline uptake by the high affinity choline transporter (CHT) is the rate-limiting step in acetylcholine synthesis. Induction of CHT is therefore a critical step in cholinergic differentiation, and we examined the developmental expression of CHT in cholinergic sympathetic neurons that innervate rodent sweat glands. During postnatal development the earliest sympathetic axons in the rear footpads are noradrenergic, containing intense tyrosine hydroxylase immunoreactivity and lacking CHT-immunoreactivity (CHT-IR). By postnatal day 7 (P7) in mouse, and P10 in rat, weak CHT-IR appeared in axons associated with the sweat gland anlagen. CHT staining intensity increased during the following weeks in conjunction with plexus arborization and gland maturation. The pattern of CHT-immunoreactivity (CHT-IR) in the sweat gland innervation was similar to staining for the vesicular acetylcholine transporter and vasoactive intestinal peptide. Immunoblots of tissue from sympathectomized rats confirmed that most of the CHT in footpad was contained in sympathetic neurons. Although CHT expression has been reported in noradrenergic sympathetic neurons of the superior cervical ganglion, these data indicate that in the sympathetic neurons projecting to sweat glands CHT is present at detectable levels only after association with the glands.

Absence of cholinergic sympathetic innervation from limb muscle vasculature in rats and mice.

Although the existence of cholinergic sympathetic vasodilatory innervation in limb muscle vasculature is well established for some species, previous pharmacological studies have failed to reveal the presence of such innervation in rats. Recently, Schafer and colleagues [Schafer, M.K., Eiden, L.E., Weihe, E., 1998. Cholinergic neurons and terminal fields revealed by immunohistochemistry for the vesicular acetylcholine transporter. II. The peripheral nervous system. Neuroscience 84(2), 361-376] reported that vesicular acetylcholine transporter immunoreactivity (VAChT-IR), a marker for cholinergic terminals, is present in the innervation of the microvasculature of rat hindlimb skeletal muscle and concluded that rats possess cholinergic sympathetic innervation of limb muscle vasculature. Because of our interest in identifying targets of cholinergic sympathetic neurons, we have analyzed the transmitter properties of the innervation of muscle vessels in rat and mouse limbs. We found that the innervation of vasculature in muscle is noradrenergic, exhibiting robust catecholamine histofluorescence and immunoreactivity for tyrosine hydroxylase (TH) and the peptide transmitters, neuropeptide Y (NPY) and occasionally vasoactive intestinal peptide (VIP). In contrast, cholinergic phenotypic markers,VAChT-IR and acetylcholinesterase (AChE) activity, are absent. Neuron cell bodies in sympathetic ganglia, retrogradely labeled with injections of tracer into limb muscles, also lacked VAChT but contained TH-IR. The innervation of large extramuscular feed arteries in hindlimbs was also devoid of cholinergic markers, as were the cell bodies of sympathetic neurons innervating extramuscular femoral arteries. These results, like those of previous physiological studies, provide no evidence for the presence of cholinergic sympathetic innervation of muscle vasculature in rats or mice.

Catecholamines are required for the acquisition of secretory responsiveness by sweat glands.

The sympathetic innervation of sweat glands undergoes a developmental change in transmitter phenotype from catecholaminergic to cholinergic. Acetylcholine elicits sweating and is necessary for development and maintenance of secretory responsiveness, the ability of glands to produce sweat after nerve stimulation or agonist administration. To determine whether catecholamines play a role in the development or function of this system, we examined the onset of secretory responsiveness in two transgenic mouse lines, one albino and the other pigmented, that lack tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine synthesis. Although both lines lack TH, their catecholamine levels differ because tyrosinase in pigmented mice serves as an alternative source for catecholamine synthesis (Rios et al., 1999). At postnatal day 21 (P21), 28 glands on average are active in interdigital hind footpads of albino TH wild-type mice. In contrast, fewer than one gland is active in albino TH null mice, which lack catecholamines in gland innervation. Treatment of albino TH null mice with DOPA, a catecholamine precursor, from P11 to P21 increases the number of active glands to 14. Pigmented TH null mice, which have faint catecholamine fluorescence in the developing gland innervation, possess 12 active glands at P21, indicating that catecholamines made via tyrosinase, albeit reduced from wild-type levels, support development of responsiveness. Gland formation and the appearance of cholinergic markers occur normally in albino TH null mice, suggesting that catecholamines act directly on gland cells to trigger their final differentiation and to induce responsiveness. Thus, catecholamines, like acetylcholine, are essential for the development of secretory responsiveness.

A method for counterstaining tissues in conjunction with the glyoxylic acid condensation reaction for detection of biogenic amines.

A method is described for counterstaining tissue for use with the glyoxylic acid reaction for visual detection of biogenic amines. Counterstaining is achieved by addition of the fluorescent dye malachite green to the sucrose-phosphate-glyoxylic acid (SPG) solution used for processing of cryostat sections of unfixed tissues. When bound to tissues, the dye provides red-orange fluorescence of background tissue, which contrasts well with the green to yellow fluorescence induced by the glyoxylic acid reaction product formed with biogenic amines. The counterstaining technique is demonstrated in a number of catecholamine-containing peripheral tissues and is compared to sections that were processed without counterstaining.

Target-dependent development of the vesicular acetylcholine transporter in rodent sweat gland innervation.

Descriptive studies have delineated a developmental change in neurotransmitter phenotype from noradrenergic to cholinergic in the sympathetic innervation of sweat glands in rodent footpads. Transplantation and culture experiments provide evidence that interactions with the target tissue induce this change. Recent studies with an antiserum that recognizes the vesicular acetylcholine transporter (VAChT) suggest, however, that the development of cholinergic function in sympathetic neurons, including those that innervate sweat glands, occurs prior to and does not require target contact. To clarify these apparently contradictory findings, we directly compared the appearance of VAChT immunoreactivity in the sympathetic neurons that innervate sweat glands with the time that axons contact this target. We find that VAChT immunoreactivity is not detectable in either the axons or cell bodies of sweat gland neurons until several days after target innervation. Before and during VAChT acquisition, the developing sweat gland innervation contains vesicular stores of catecholamines. An analysis of mutant mice that lack sweat glands was undertaken to determine whether VAChT expression requires target interactions and revealed that VAChT does not appear in the absence of glands. These findings, together with previous studies, confirm the target dependence of cholinergic function in the sympathetic neurons that innervate sweat glands.

Overexpression of nerve growth factor in epidermis disrupts the distribution and properties of sympathetic innervation in footpads.

Sympathetic and sensory neurons form distinct axonal arborizations in several peripheral targets. The developmental mechanisms responsible for partitioning sympathetic and sensory axons between potential target tissues are poorly understood. We have used rodent footpads to study this process because three populations of peripheral axons innervate topographically segregated targets in the footpad; cholinergic sympathetic axons innervate sweat glands, noradrenergic sympathetic axons innervate blood vessels, and sensory axons form a plexus at the epidermal/dermal junction. To examine how nerve growth factor (NGF), a trophic and survival factor for sympathetic and some sensory neurons, may contribute to the generation of the patterned distribution of axons among targets, we studied transgenic mice (K14-NGF mice) in which NGF expression was significantly increased in the epidermis. Whereas the temporal sequence in which sensory and sympathetic fibers arrived in the footpad was not affected, the normal partitioning of axons between target tissues was disrupted. The two sympathetic targets in footpads, sweat glands, and blood vessels lacked substantial innervation and instead a dense plexus of catecholaminergic sympathetic fibers was found commingled with sensory fibers in the dermis. Those sympathetic fibers present in sweat glands expressed an abnormal dual catecholaminergic/cholinergic phenotype. Our findings indicate that overexpression of NGF in skin interferes with the segregation of sensory and sympathetic axonal arbors and suggests a role for target-derived NGF in the establishment of distinct axonal territories. Our data also suggest that by determining where axon arbors form, NGF can indirectly influence the phenotypic properties of sympathetic neurons.

Sympathetic axons pathfind successfully in the absence of target.

To determine whether sympathetic axons require the presence of a peripheral target to grow to the correct destination, we examined the developing footpad innervation in tabby mutant mice which lack sweat glands. Despite the absence of sweat glands, noradrenergic sympathetic axons are transiently present in the presumptive target area and avoid the more distal epidermal/dermal domain occupied by sensory axons. Since sympathetic axon pathfinding was not dependent upon the target tissue, we compared the subsequent development of sweat gland axons in tabby footpads with that in control footpads. In wild-type mice, the gland-associated axonal plexus expands considerably as the secretory tubule enlarges and coils. This expansion, however, does not occur in tabby mice. The sweat gland innervation of wild-type mice loses catecholamines and acquires AChE activity and vasoactive intestinal peptide immunoreactivity. In tabby mutant mice, catecholaminergic fibers remain in the glandless footpads for 2 weeks and fail to acquire AChE or vasoactive intestinal peptide. In contrast to the altered development of gland innervation in tabby, the development of the innervation of footpad blood vessels was unaffected. Our observations indicate that the target is not required to direct sympathetic axons to the presumptive gland region of the footpad. In the absence of the target tissue, however, gland-targeted sympathetic axons retain an immature morphology and transmitter phenotype and then disappear.

Simultaneous assessment of myocardial perfusion and left ventricular function during transient coronary occlusion.

OBJECTIVES: We used technetium-99m sestamibi imaging to evaluate the magnitude of changes in left ventricular function and perfusion and to investigate their interdependence during transient coronary occlusion. BACKGROUND: Transient coronary occlusion during coronary angioplasty provides a unique opportunity for examining the effects of acute myocardial ischemia on left ventricular function and perfusion. METHODS: Thirty-five patients with normal left ventricular function underwent first-pass radionuclide angiography with technetium-99m sestamibi using a multicrystal gamma camera during balloon occlusion of a coronary artery. Single-photon tomography was performed 2.1 +/- 1.7 h later. Subsequently, all scans were repeated at rest. RESULTS: The mean size +/- SD of the perfusion defect during coronary occlusion was 23 +/- 18%, with significantly larger defects observed for occlusions of the left anterior descending coronary artery (39 +/- 20%) than for occlusions of the left circumflex (15 +/- 11%) or right (15 +/- 9%) coronary artery (p < 0.05). The mean change in ejection fraction from recovery to occlusion was -17 +/- 17% and was significantly larger for left anterior descending (-26 +/- 21%) and left circumflex (-15 +/- 11%) than for right (-8 +/- 10%) coronary artery occlusions (p < 0.05). For the entire group, ejection fraction during occlusion correlated significantly with perfusion defect size (r = 0.63, p = 0.0004), whereas the extent of ischemic myocardium correlated with the decrease in ejection fraction (r = 0.69, p = 0.0001). The defects present during occlusion reversed within a few hours. CONCLUSIONS: Changes in left ventricular function and perfusion develop pari passu during coronary occlusion and are more severe when the left anterior descending artery is occluded. Although a significant correlation exists between the extent of the perfusion defect and the severity of the decrease in ejection fraction, there is a substantial individual variation with respect to changes in both myocardial perfusion and ventricular function during acute coronary occlusion.

Comparison of ventricular function in atrial rate adaptive versus dual chamber rate adaptive pacing during exercise.

The hemodynamic effects of two different pacing modes--rate adaptive atrial (AAIR) versus dual chamber (DDDR) pacing--were assessed in 12 patients with DDDR pacemakers during upright bicycle exercise first-pass radionuclide angiography using a multiwire gamma camera with tantalum-178 as a tracer. All patients had sinus node disease with intact AV conduction. Patients exercised to the same heart rate in random order in these two different pacing modes, AAIR and DDDR with AV delay (of 100 msec) selected to maintain 100% ventricular capture. Cardiac output increased significantly above baseline values during exercise in both pacing modes: 154 +/- 41% (mean +/- SEM, P = 0.002) with AAIR, versus 95 +/- 24% (P = 0.004) with DDDR (P = NS between the two modes). The peak filling rate, likewise, increased in both pacing modes (2.3 +/- 0.21 end-diastolic volumes/sec to 3.8 +/- 0.31 end-diastolic volumes/sec in AAIR [P = 0.0004] and 2.2 +/- 0.18 end-diastolic volumes/sec to 3.4 +/- 0.27 end-diastolic volumes/sec in DDDR [P = 0.0008]). LV ejection fraction was normal at rest (60 +/- 4%, SEM) and did not significantly change with submaximal exercise in either pacing mode (both 56%, P = NS). No significant changes in end-diastolic volume or stroke volume indexes occurred with exercise in either pacing mode. Our study demonstrates that in patients with normal resting LV function, AAIR and DDDR pacing are equally effective in attaining appropriate increases in cardiac output and LV filling during exercise.

Safety of single-site adenosine thallium-201 scintigraphy.

The diagnostic accuracy, safety and tolerance of adenosine thallium scintigraphy have been reported using a 2-site intravenous infusion with either a titrated or fixed-dose protocol. A single-site infusion would considerably simplify the test procedure, but its safety must be established before it can be recommended. Accordingly, 400 consecutive patients who had adenosine and thallium-201 administered through the same intravenous line were classified into 2 groups. Group I (n = 201) patients received a 7-minute titrated intravenous infusion of adenosine, with an initial dose of 50 micrograms/kg/min that increased at 1-minute intervals to a maximum of 140 micrograms/kg/min. Group II (n = 199) patients received a fixed dose of adenosine at 140 micrograms/kg/min for 6 minutes. Adenosine significantly (p < 0.001) increased heart rate and decreased systolic blood pressure by similar amounts in both groups. Adverse effects occurred more often (88 vs 71%, p < 0.001) and started earlier (2.8 vs 3.6 minutes, p < 0.001) in group II. There was no significant difference in the occurrence of second- and third-degree atrioventricular block between the 2 groups (4.0 vs 5.0%); however, chest pain, flushing and nausea were all more frequent in group II. Severe side effects were seldom seen in either group and occurred in 9 group I and 8 group II patients. Scintigraphic findings were similar in both groups. Transient perfusion defects were seen more often in patients with than without second- or third-degree atrioventricular block (42 vs 21%, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of acute, transient coronary occlusion on global and regional right ventricular function in humans.

OBJECTIVES: The aim of this study was to investigate the changes in right ventricular function during acute coronary occlusion produced by inflating a coronary angioplasty balloon catheter. BACKGROUND: Alterations in right ventricular function are well known to occur in patients with acute myocardial infarction or ischemic cardiomyopathy. However, the changes in right ventricular function resulting from acute, transient coronary occlusion of each of the major coronary arteries have been scantily studied, perhaps because of serious limitations of currently available technology. METHODS: A newly designed, mobile, multiwire gamma camera, in combination with generator-produced tantalum-178, affords high count rate first-pass radionuclide angiography and is thus ideal for studying right ventricular function at the bedside. Accordingly, 46 patients underwent first-pass radionuclide angiography at baseline and during transient coronary occlusion induced by a coronary angioplasty balloon catheter. RESULTS: A significant, albeit modest, decrease in global right ventricular ejection fraction occurred during occlusion of the left anterior descending (from 42.9 +/- 9.3% to 39 +/- 8.7%, p < 0.05) and left circumflex (from 44 +/- 9.1% to 38.8 +/- 7.9%, p = 0.03) coronary arteries, but diagonal artery occlusion caused no significant change in right ventricular ejection fraction. Occlusion of the right coronary artery proximal (but not distal) to the acute marginal branch caused a significant decrease in right ventricular ejection fraction (from 42.6 +/- 4.7% to 35.7 +/- 7.2%, p < 0.01). Although occlusion of the left anterior descending, left circumflex and proximal right coronary arteries all caused significant deterioration in regional right ventricular function, only proximal right coronary occlusion caused right ventricular dilation (p < 0.005). CONCLUSIONS: Significant impairment of right ventricular function occurs during transient occlusion of the left anterior descending, left circumflex and proximal right coronary arteries, but only occlusion of the latter causes acute right ventricular dilation, probably as a result of ischemia.

Quantification of left ventricular performance during transient coronary occlusion at various anatomic sites in humans: a study using tantalum-178 and a multiwire gamma camera.

To study the functional significance of transient coronary occlusion on systolic and diastolic left ventricular function relative to the anatomic site of occlusion, first-pass radionuclide angiography with a mobile multiwire gamma camera using tantalum-178 (dose activity less than or equal to 84 mCi/elution) was performed in 46 patients undergoing balloon coronary angioplasty. First-pass images were acquired immediately before angioplasty and during the last 30 s of a 60-s balloon inflation in 23 left anterior descending arteries, 18 right coronary arteries, 8 circumflex arteries and 3 diagonal coronary arteries. Occlusion of the left anterior descending artery resulted in significant decreases in left ventricular ejection fraction (54.6 +/- 12.7% to 32.3 +/- 10.6%, p = 0.0001) and peak filling rate (2.48 +/- 0.68 to 1.75 +/- 0.64 end-diastolic volumes/s, p = 0.0001), accompanied by severe abnormalities in regional function and left ventricular dilation. Right coronary artery occlusion caused inferior hypokinesia, but did not significantly change left ventricular ejection fraction (48.5 +/- 12.4% vs. 45.8 +/- 12.5%, p = NS) or peak filling rate (2.05 +/- 0.81 vs. 2.09 +/- 0.81 end-diastolic volumes/s, p = NS). Circumflex artery occlusion resulted in mild wall motion deterioration and a borderline decrease in ejection fraction (54.7 +/- 11.4% to 50.5 +/- 12%, p = 0.057). Diagonal artery occlusion did not cause significant changes in left ventricular ejection fraction or filling rate. The decrease in left ventricular ejection fraction during coronary occlusion was 9 +/- 25% and 27 +/- 22%, respectively, in those arteries with and without collateral supply (p = 0.052). These data provide strong evidence for the critical importance of the left anterior descending artery and the secondary role of the other coronary arteries in maintaining global systolic and diastolic left ventricular function and suggest a protective role of collateral vessels during coronary occlusion.

Incorrect use of metered dose inhalers by medical personnel.

We administered a questionnaire and observed usage of a placebo metered dose inhaler (MDI) among 35 physicians, 14 nurses, and 12 respiratory therapists. Ninety-two percent of the respiratory therapists performed at least four of seven steps correctly, compared with 65 percent of house staff physicians, 57 percent of nurses, and 50 percent of nonpulmonary faculty. Most participants followed package insert instructions, while only 18 percent followed recent recommendations for proper MDI use. We conclude that (1) medical personnel should have additional instruction in proper MDI usage and (2) respiratory therapists and nurses can play a prominent role in instructing patients in their proper use.

Development and clinical performance of an automated, portable tungsten-178/tantalum-178 generator.

An automated, portable 178W/178Ta generator system has been developed for use in first-pass radionuclide angiography studies with the multiwire gamma camera. Eluant (0.03N HCI, 0.1% H2O2) and buffer (0.13 N Na2HPO4) are delivered with a dual channel peristaltic pump. The generator column is a borosilicate glass tube with 30 microns fused glass frit containing 0.75 ml AG1X8 anion exchange resin. This column and associated plumbing are assembled, integrally autoclaved, and then connected to sterile eluant and buffer containers. Automatic push-button elution directly into an injection syringe is provided. Three such generators have been employed in the study of 78 patients in the catheterization laboratory utilizing a mobile, multiwire gamma camera. Over a 3-mo period, 301 sterile pyrogen-free doses ranging from 15 to 99.5 mCi were supplied with a mean breakthrough level of 2.1 +/- 3.6 microCi. This automated, portable, high-yield 178W/178Ta generator represents a major advancement that will significantly facilitate first-pass radionuclide angiography with 178Ta and the multiwire gamma camera.

Respiratory syncytial virus infection among intubated adults in a university medical intensive care unit.

Respiratory syncytial virus is the major cause of lower respiratory tract infection in children. Adults who are immunocompromised, aged, institutionalized, and/or have underlying medical diseases may be at risk for severe RSV infection. Intubated adults in an MICU were evaluated for evidence of RSV infection. Respiratory secretions were analyzed by cell culture and RSV EIA. Serologic testing was obtained. Respiratory secretions from MICU personnel with acute respiratory symptoms and patients admitted for pneumonia, asthma, or COPD also were screened. Five of 11 intubated patients had evidence of RSV infection. One of seven MICU employees and four of 48 ward patients had RSV-positive respiratory secretions. During community outbreaks of RSV infection, adults admitted to an MICU already may be infected with RSV; those admitted for other reasons are at risk for nosocomial infection. Patients occupying other hospital units and personnel may be instrumental in the nosocomial dissemination of RSV.

Catamenial hemoptysis: a case report and review of the literature.

A young woman with catamenial hemoptysis and pleuritic chest pain is reported. She had two living children and had undergone three abortions and a tubal ligation followed by menorrhagia and dysmenorrhea. Fiberoptic bronchoscopy revealed no abnormalities, but computed tomograms of the chest revealed bilateral lung densities, which waxed and waned during the menstrual cycle. When characteristic clinical and CT findings are present, bronchoscopy is not necessary for the diagnosis of pulmonary endometriosis.

Pulmonary fibrosis as the initial manifestation of scleroderma.

We report a patient who developed pulmonary fibrosis before the appearance of cutaneous scleroderma. This unusual clinical presentation has been infrequently reported in the English literature. Recognition that pulmonary disease may occur before extensive skin changes in scleroderma is important to ensure proper management.

Aplasia of the cervical internal carotid artery and malformation of the circle of Willis associated with Klippel-Trenaunay syndrome. Case report.

The authors describe the radiographic findings in a patient with Klippel-Trenaunay syndrome who also had aplasia of the left internal carotid artery and a very unusual malformation of the circle of Willis. This constellation of clinical and radiographic findings is unique and has not been previously reported in the medical literature.