A tethered sonde for obtaining detailed micrometeorological soundings in the lower 500 m of the atmosphere is described. The instrument was developed to be directly compatible with the current audio-modulated radiosonde used extensively in North America; the radiosonde thermistor and hygristor are employed to measure temperature and humidity, but with a higher degree of sensitivity. A sensitive pressure transducer was specially designed to provide accurate height measurements, and sensor sequencing is accomplished by a miniature servo-switching system. Techniques of data telemetry, automatic recording and computation are very similar to those of the radiosonde system, and ancillary sensors can be adapted readily for special sounding requirements. The system is very convenient to operate, and flights made thus far have shown excellent detail in temperature and humidity profiles.

An instrument for the detailed study of temperature-height profiles within the lower 500 m of the atmosphere is described. The instrument is carried aloft by tethered balloon and, unlike most other tethered sounding instruments, transmits a continual sequence of measurements regardless of ascent rate. Chronometric principles are employed for data telemetry, permitting the use of simple and economical ground receiving equipment. The sonde has been used quite successfully during the past few years for land and ship-based soundings at various micrometeorological field research sites in Canada.

The work described in this chapter has indicated that improved outcome from an experimental head injury model can be achieved by drugs which are non-diuretic derivatives of loop diuretics, namely indanyl and fluorenyl compounds which are derivatives of ethacrynic acid. These drugs were originally identified by us on the basis of their efficacy in inhibiting [K+]-stimulated, HCO3(-)-dependent swelling of brain cerebrocortical slices. Swelling of glial cells (astrocytes) has long been known to be associated with such slice swelling and astrocyte swelling is a major locus of cytotoxic or cellular brain edema. Qualitative and quantitative electron microscope studies have shown that L644,711, a particularly effective member of the fluorenyl class of drugs, inhibits astrocytic swelling associated with an experimental animal head injury model. We have suggested that astrocytic swelling in pathological states may be partly due to activation of Cl-/HCO3- and Na+/H+ exchange systems driven by increased astrocytic intracellular hydration of CO2, and recent work has indeed shown that the ability of the indanyl and fluorenyl drugs to inhibit brain slice swelling and protect against head injury correlates closely with their ability to inhibit Cl-/HCO3- exchange. All these data suggest that astrocytic swelling, which seems to precede neuronal degeneration and breakdown of the blood-brain barrier, is deleterious and that prevention of such swelling can lead to effective therapy. We have used primary astrocytic cultures to explore reasons why astrocytic swelling could be harmful. Exposing such astrocytes to hypotonic medium causes rapid swelling with a slower return to normal volume in the continued presence of hypotonic medium, a process known as regulatory volume decrease or RVD. Such RVD is associated with marked release of several amino acids, including L-glutamate. L644,711 and other Cl-/HCO3- transport inhibitors such as SITS and furosemide, but not the selective Na+ + K+ + 2Cl- co-transport inhibitor bumetanide, inhibit such swelling-induced release of L-glutamate. Thus, L644,711 and other drugs may be effective in promoting recovery from head injury and other pathological states in which astrocytic swelling occurs either by initially preventing the swelling or inhibiting the release of excitotoxic excitatory amino acids if swelling does occur, perhaps depending at what time the drug is given.

We present qualitative and quantitative ultrastructural observations on the changes induced in neuroglia and blood vessels of gray matter of cat brain by an experimental acceleration-deceleration injury which, when used alone, causes negligible morbidity and mortality, but, when combined with systemic hypoxia, leads to coma and delayed death in approximately 50% of experimental subjects. An increase in the proportion of neuropil occupied by astrocytic cytoplasm is detectable qualitatively in layer Vb of pericruciate cortex 20 min after injury without hypoxia, and is maximal (22%, as measured morphometrically, vs 11.4% in controls) 40 min afterward. Near-normal values (14.1%) are obtained 100 min following the insult. If trauma is succeeded 40 min later by a 60-min period of hypoxia, there is prolongation of astrocytic edema and other neuroglial accompaniments of the traumatic lesion, such as aggregation of nuclear nucleoprotein granules and, in astrocytes, fusion of rosette ribosomes and enlargement of mitochondria. A decrease in luminal area occurs in capillaries 40 min after trauma applied alone. Hypoxia without trauma leads to a significant increase in capillary luminal area, which, however, is abolished when trauma precedes the hypoxic interlude. Intravenous injection of a non-diuretic, fluorenyl derivative (L-644,711) of (aryloxy)alkanoic acid loop diuretics, completely prevents the astrocytic swelling ordinarily present 40 min after acceleration-deceleration injury. Also, L-644,711 improves mortality and morbidity scores in cats subjected to trauma with hypoxia. We suggest that astroglial swelling may be a critical step in the evolving pathology of this head injury model and its prevention, as by L-644,711 administration, may have relevance to the treatment of cerebral edema in human head injury and other clinical disorders accompanied by astrocytic swelling.

AbstractDie im Titel genannten Verbindungen (XIII) werden auf den im Schema angegebenen Reaktionswegen ausgehend vom Dichloranisol (I) bzw. dem Arvloxyessigsäureester (XIV) hergestellt.

Our initial paper discussed brain edema resulting from traumatic head injury and the need for specific and effective agents to treat the disorder and disclosed a novel approach for the discovery of a drug of this kind. The current study describes the synthesis of a series of [(2,3,9,9a-tetrahydro-3-oxo-9a-substituted-1H-fluoren-7-yl)oxy]alk anoic acids and their analogues. These compounds were evaluated in an in vitro cerebrocortical tissue slice assay for their relative potencies in inhibiting K+ + HCO3- induced swelling. Structural modification at a number of sites in the "lead" compound revealed that significant biological activity was inherent only within a very narrow range of structural types. The observation that nearly all the biological activity resided in one of the two enantiomers demonstrated the marked stereospecificity of the most active compounds. One of the most potent compounds, (R)-(+)-[(5,6-dichloro-2,3,9,9a-tetrahydro-3-oxo-9a-propyl-1H-fluoren -7-yl) oxy]acetic acid ((+)-5c), exhibited a dose-response relationship in the in vivo acceleration/deceleration brain edema assay, and the data from the two highest doses were statistically significant. Electron microscopic examination demonstrated that the perivascular astroglial swelling that arises from this procedure is abolished in the animals treated with (+)-5c. This compound is currently being evaluated for its clinical efficacy and safety in the treatment of traumatic head injury.

Cat cerebrocortical slices incubating in medium containing normal K+ concentrations were exposed to a number of different transmitters. Norepinephrine, histamine and adenosine or 2-chloroadenosine caused increased swelling of the slices associated with an increased Na+ and Cl− content. These effects were seen only when both Cl− and HCO3− were present in the medium, and were inhibited by a number of anion transport inhibitors. These characteristics were identical to those of the HCO3−-dependent component of the swelling induced by high K+ levels in the medium. Other transmitters, namely 5-hydroxytryptamine, dopamine, and γ-amino butyric acid, were ineffective. The effects of norepinephrine, histamine and 2-chlorcadenosine were antagonised by propranolol and phentolamine, chlorpheniramine and diphenhydramine, and theophylline respectively. These antagonists also inhibited HCO3−-dependent, K+-stimulated swelling. The transmitters which induced swelling also stimulated the carbonic anhydrase activity of cerebrocortical slices. We conclude from these data that the HCO3−-dependent component of K+-stimulated swelling may be due to K+-stimulated release of transmitters. Furthermore, the fact that the transmitters which induce swelling have also been reported to be most effective in increasing cAMP content in both brain slices or cultured astrocytes is consistent with the swelling response being mediated via cAMP-induced changes and being predominantly localized to astrocytes.

Blunt and ischemic injuries of the brain have been shown to result in swelling that is predominantly limited to a single cell type, the astrocyte, within the complex cellular mosiac of cerebral gray matter. Evaluation of various diuretic (aryloxy)acetic acids in vitro using incubating cat brain slices and primary astrocyte cultures identified compounds with marked ability to inhibit brain tissue swelling. Some of the compounds significantly reduced the mortality and morbidity following acceleration/deceleration brain injury in anesthesized cats. A variety of (indanyloxy)alkanoic acids were synthesized which were analogous to the dually active (indanyloxy)acetic acids. Some of the 4-(indanyloxy)butanoic acids were found to be devoid of diuretic activity but to possess equal or greater activity than the dually active compounds in the in vitro and in vivo brain assays. Selected examples from both the (indanyloxy)acetic and 4-(indanyloxy)butanoic acid series showed marked chiral effects, with one enantiomer generally exhibiting a much greater activity than the other. A clinical study of severely head-injured patients treated with ethacrynic acid demonstrated a significantly improved outcome when compared to controls. These data suggest a clinical advantage for the nondiuretic (aryloxy)alkanoic acids which possess in vitro and in vivo activities in the cat brain assays that are comparable or superior to dually active compounds.

Intracranial pressure (ICP), cardiopulmonary function, and the degree of neurological dysfunction were measured in 13 patients with serious head injury to determine the relationship of these indices to the development of delayed pulmonary dysfunction. All patients had serious isolated head injury with Glasgow Coma Scale scores of 7 or less 6 hours after injury and elevated ICP at the time of admission to the protocol. Three patients developed arterial pO2 of less than or equal to 80 torr despite the initiation of elevated inspired oxygen fraction (FIO2 greater than or equal to 0.5) and positive end expiratory pressure (greater than or equal to 5 cm H2O. One of these three patients had a decline in neurological function, quantified by the Albany Head-Injury Watch Sheet, associated with hypoxemia. The only patients who developed intrapulmonary shunt fractions of more than 15% were five patients who had increased pulmonary vascular resistance (PVR) and elevated or increasing cardiac index, suggesting persistent perfusion to areas of the lung which normally are hypoperfused due to hypoxic pulmonary vasoconstriction. This mismatching of the distribution of ventilation and perfusion was confirmed using the multiple inert gas elimination technique in two patients with an increased shunt fraction. Unperfused gas exchange units were also found to be present, as confirmed by an abnormal multiple inert gas elimination techniques, high PVR and dead space/tidal volume ratio (VD/VT), and low extravascular lung water. Abnormalities of ICP and cerebral perfusion pressure could not be correlated with changes in any of the cardiopulmonary functions studied.

Cardiopulmonary hemodynamics after serious head injury were measured in eight patients to determine the relationship of these responses to intracranial pressure and alterations in pulmonary gas exchange. All patients had similar degrees of craniocerebral injury when assessed by the Glasgow Coma Scale, computerized tomographic scan, and initial intracranial pressure measurement. Intrapulmonary shunt fractions were elevated in all patients (range 11–29%) supporting the hypothesis that pulmonary dysfunction following isolated head injury is a distinct nosological entity. However, no correlation was found between level of intracranial pressure and any of the cardiopulmonary hemodynamic parameters studied. Patients surviving their injury initially showed a low cardiac index (2.56 ± 0.21 liters/min/M2) which subsequently became normal (3.77 ± 0.40 liters/min/M2). There was no evidence of increased pulmonary vascular resistance in these patients (95 ± 15 dyne-sec/ cm5). In contrast, patients dying of their injury generally had high pulmonary vascular resistance on admission (284 ± 74 dyne-sec/cm5) and a low cardiac index throughout their hospital course (1.87 ± 0.43 liters/min/M2). The cause of low cardiac index seen in this study is unknown. The abnormally high pulmonary vascular resistance in nonsurvivors may be a primary response of the pulmonary vasculature to serious head injury and reflect the severity of that injury.

Primary cultures of normal astroglia started from the cerebral hemispheres of neonatal rats took up dopamine (DA) and norepinephrine (NE) in the concentration range of 10−7 to 10−4M and metabolized each to their respective principal central nervous system products by the actions of both catechol-0-methyl transferase and monoamine oxidase. At 10−7M, uptake of 3H labelled DA and NE was inhibited by omission of Na+, addition of ouabain or lowered temperatures. Uptake at 10−4M was considerable but was Na+-independent. Only Na+-independent uptake was seen in primary cultures started from the meninges of neonatal rats. These data suggest that astroglial cells in the CNS have a high affinity uptake system for catecholamines, and such uptake is followed by catecholamine metabolism.

The intact cerebral cortices of cats were exposed in vivo under normothermic conditions and superfused with isotonic artificial cerebrospinal fluid containing added 0.125 mM adenosine. This resulted in chloridecation-rich cerebrocortical swelling which was shown by electron microscopy to be associated with an expanded astroglial compartment. The addition of DCPIB, a non-diuretic acylaryloxyacid analogue of ethacrynic acid and an inhibitor of coupled chloride-cation transport in cerebral cortex in vitro, totally blocked astroglial swelling and the concomitant increases in tissue ion contents. These studies support our previous experiments on the mechanism of formation of astroglial swelling. The pathological consequences of astroglial swelling and the clinical applications of these findings are discussed.

Most studies of clinically relevant cerebral edema emphasize the effect of added tissue fluid in white matter on gross distortion with transtentorial and subfalcine brain herniation. Our recent studies on altered tissue fluid compartmentation in cerebral gray matter suggest that significant microdistortion of relationships of capillaries to subserved tissue follows swelling of astroglia therein. Grave consequences to solute and gas exchange in focal regions may well be expected and are emphasized. The elucidation of the mechanisms of formation and inhibition of astroglial swelling by chemical agents, including chemically useful acylaryloxyacetic acid derivatives, are discussed. Furthermore, the effect of these agents in altering mortality and morbidity in a controlled, random study of animal head injury is presented.

The uptake and efflux of Cl- were measured in primary astroglial cultures from neonatal rat brain using 36Cl- as a tracer. Both uptake and efflux were found to be inhibited by the specific anion inhibitor SITS. The rate of Cl- efflux showed a broad optimum at pH values greater than 7.5, and both this pH dependence and the effect of SITS suggests that these cells contain a Cl- in equilibrium Cl- or Cl- in equilibrium HCO3- exchange carrier similar to that described in erythrocytes. In addition, the cells rapidly lost Cl- when placed in media of decreasing Cl- concentrations, and ploting the initial rate of uptake of 36Cl- as a function of external Cl- concen-ration gave an apparent Km for Cl- uptake of 56 mM. Pretreatment of these cultures with DBcAMP is known to cause the cells to form numerous processes, resulting in their morphology more closely resembling that of astroglia in brain. Treatment with DBcAMP resulted in decreased equilibrium levels of 36Cl- and a small decrease in the initial rate of uptake of 36Cl-, but did not affect inhibition by SITS. Addition of Na+ to the cells suspended in Na+-free media specifically increased the rate of acidification of the medium. These observations suggest that these cells have both Cl- in equilibrium HCO3- and Na+ in equilibrium H+ exchange processes which, if these cultures can be considered to be representative of cells in vivo, may also occur in astroglial cells in the central nervous system. Based on these results and other work, a model is proposed by which these processes would lead to the astroglial swelling which is often observed in vivo in pathological conditions.

Histochemical, electron microscopic, and morphometrical techniques were employed in the determination of the effects attributed to K+-induced cerebrocortical swelling on cat cerebrocortical capillary diameter, length, surface area, volume, and minimal intercapillary distance.