In languid grainy waves, seas of sand flow over parts of our landscape, cresting and tumbling into deep troughs. The West has some of the largest and most remarkable dune systems in North America, from coastal strands stretching 7 miles long to inland hills peaking at 700 feet.
Since prodding up a dune can be tiring, consider going in the morning, when sand is still hard-packed and a bit moister. Sand is usually firmer on the windward (stoss) slope than it is on the steeper slipface. If you can't start early, wait until late in the afternoon, since winds commonly pick up at midday as the temperature rises. It's wise to wear sunblock, a wide-brimmed hat, and sunglasses to protect against reflected sunshine, and a bandanna and long-sleeve shirt to shield you nfrom blowing sand. High-topped boots will help keep sand out. Always carry a supply of water. In desert dunes, watch for rattlesnakes and scorpions.If no MB activity is demonstrated, it may be because the infarct is of such recent onset that insufficient time has elapsed to detect its presence in the blood. Serial CK-MB determinations are required in this instance to establish a lab diagnosis of acute MI.How high must concentrations of MB activity be before they are considered pathologic? Concentrations greater than 20 IU per liter are definitely elevated. There is a gray zone in the range of about 12-20 units, and values less than 12 units are observed among normal individuals without either cardiac or voluntary muscle damage.The diagnosis of acute myocardial infarction poses no problem in a patient who presents with shock, diaphoresis, an ashen gray appearance, and crushing substernal chest pain radiating down the left arm. Anyone who has once witnessed this classical presentation will be able to make the diagnosis in the future.CK-MB activity is present in the serum of normal individuals, albeit in small concentrations. The critical question is where does one place the cutoff between normal and abnormal concentrations, knowing that overlap exists between normals and patients who have recently sustained acute MIs?About 20 years ago, enzyme panels were introduced to confirm or exclude acute MI among patients with atypical presentations whose ECGs were equivocal. Enzymatic confirmations consisting of CK, SGOT, and LDH were employed initially. Characteristic time-dependent elevations of these enzymes would confirm the diagnosis, and approximate date, of a presumed acute MI. But false-positive CK elevations resulting from intramuscular injections, and nonspecific elevations of SGOT and LDH, limited the usefulness of these panels. About seven years ago, this triad was replaced with an equally sensitive but much more specific panel consisting of total CK and LDH as well as isoenzymes of each.1, 2Today, the image of dunes as barren, lifeless places has changed, and the growing appreciation of these sand-bound ecosystems is reflected in fervent efforts to protect them. Offroad vehicles have been banned from some preserves and restrictued from entering parts of others. One area, Eureka Dunes is a newly designated national natural landmark.Since an elevated CK-MB is not, per se, an indication of cardiac muscle damage, an elevation is meaningful only activity is concomitantly of MB activity is concomitantly increased. It remains to be seen whether a biologic assay or a mass assay that measures both active and inactive forms to total CK will provide thebest denominator in detecting when the concentration of CK-MB is elevated.On inland dunes, open swaths of sand provide habitat for sunloving annual plants and low-growing desert wildflowers such as white evening primrose, pink sand verbena, and violet locoweed. In the troughs between the dunes (interdune areas), you'll find scurf-pea and "blowout" or bunchgrasses, and at dune edges, taller shrubby plants like creosote bush, four-winged saltbush, honey mesquite.Certain conditions are required for dune building: an abundant souce of dry, fine- to medium-grain sand (.125 to .5 millimeters); wind that blows in a consistent direction and with sufficient strength (at least 10 mph) to move sand; and an opposing wind or land barrier to halt the sand.Regardless of the percentage of CK activity represented by the MB fraction, the absolute concentration is also significant but does not necessarily reflect damage to mayocardial tissue--all striated muscle contains small amounts of MB activity. Therefore damage to any striated muscle will elevate CK-MB, although such elevations are not pathognomic of acute MI unless the percentage of MB activity is simultaneously increased.Why is the West so dune-rich? Aridity is one major factor in the formation of our inalnd dunes. Another factor in many areas is the ample supply of building material: sand deposited in river-beds or eroded from cliffs. On our coast, ocean waves pound sandstone and granitic cliffs and deposits the lightest grains on wide beaches.Many animals have made special adaptations to their arid, sandy world. The kangaroo rat drinks no water but absorbs moisture solely through the seeds it eats. The sand treader camel cricket and fringe-toed lizard have feet that act like snowshoes.Nocturnal creatures such as snakes, beetles, and mice abound in each dune system. These animals survive by burrowing below the surface or hiding under brush by day, then emerging at night to hunt or forage. Tiny crisscrossing tracks tell of journeys and chases in the night. In the morning, look around shrubs for tracks before the wind erases them.Then there are the false positives. These relate principally to definition of terms and to methodology, although gross and random error obviously occur as well.Two criteria are employed in this regard: the absolute concentration of CK-MB activity in enzyme units per liter of serum, and the percentage of CK activity expressed relative to the total CK activity. CK-MB activity that is less than 3 per cent of the total is not considered pathologic, while a concentration greater than 5 per cent certainly is. A 4 per cent cutoff designed for high-sensitivity, low-specificity must be balanced against a 5 per cent cutoff, which provides higher specificity but a corresponding loss of sensitivity.But many patients with acute MI present with less than classical signs and symptoms: indigestion, persistent pain in the back or in the base of the neck, or an unexplained arrhythmia. How is the diagnosis of acute myocardial infarction then established?On coastal dunes, tough, salt-tolerant European dune grass stabilizes the foredunes 'those nearest the waves), and back dunes are scattered with bright yellow beach primrose, pink morning glory, Indian paintbrush, and California poppy.
Vehicular access remains a controversial issue at the Panamint Dunes near Lone Pine, California: they were closed to vehicles in 1980, but 500 acres are being considered for reopening by permit after requests from recreation groups and Inyo County officials.
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