Water exchange is routinely used in shrimp culture. However, there are few, if any, systematic investigations upon which to base exchange rates. Furthermore, environmental impacts of pond effluent threaten to hinder further development of shrimp farming in the U.S. The present study was designed to determine effects of normal (25.0%/d), reduced (2.5%/d) and no (0%/d) water exchange on water quality and production in intensive shrimp ponds stocked with Penaeus setiferus at 44 postlarvae/m2. Additional no‐exchange ponds were stocked with 22 and 66 postlarvae/m2 to explore density effects. Water exchange rates and stocking density influenced most water quality parameters measured, including dissolved oxygen, pH, ammonia, nitrite, nitrate, Kjeldahl nitrogen, soluble orthophosphate, biochemical oxygen demand, phytoplankton and salinity. Reduced‐exchange and no‐exchange treatments resulted in reduced potential for environmental impact. Mass balance of nitrogen for the system indicates that 13–46% of nitrogen input via feed is lost through nitrification and atmospheric diffusion. Growth and survival were excellent in ponds with normal exchange, reduced exchange, and a combination of low density with no water exchange. A combination of higher stocking density and no water exchange resulted in mass mortalities. Mortalities could not be attributed to a toxic effect of any one water quality parameter. Production was 6,400 kg/ha/crop with moderate stocking density (44/m2) and reduced (2.5%/d) water exchange and 3,200 kg/ha/crop with lower stocking density (22/m2) and no water exchange. Results indicate that typical water exchange rates used in intensive shrimp farms may be drastically reduced resulting in a cost savings to farms and reduced potential for environmental impact from effluent.

Implanted pellets that provide a sustained release of [D‐Ala6 Des‐Gly10] LHRH‐ethylamide (GnRHa) were used to induce maturation and ovulation of Southern flounder Paralichthys lethostigma. Of the 12 females whose ovaries contained follicles with a maximum diameter ≥500 μm, 11 ovulated for the first time within 90 h of hormone implantation. Only 1 fish with a maximum follicle diameter less than 500 μm ovulated within 2 wk after implantation. Ovulated eggs were manually stripped from the females and mixed with sperm from several males. Most females were spawned 1 to 3 times on consecutive days with variable fertility. One female was spawned 11 times producing 668,000 eggs. Fertility was evaluated by examining the incubated eggs for early stages of embryonic cleavage. The percentage of fertile eggs in subsamples of incubated eggs ranged from 7–95%. The results indicate that GnRHa implants can be used to induce repeated ovulation in this species. The variability in fertility is discussed in relation to egg quality.

Between January, 1974, and December, 1976, 123 patients with traumatic quadriplegia were admitted to the California Regional Spinal Cord Injury Care System. The spinal cord injury resulted from gunshot wounds in five, from a stab wound in one, from neck injuries with no bone damage seen on x-ray studies in 10, and from fracture dislocations of the cervical spine in 107. One-year following-up information was available on 114 patients. Neurological impairment using the Frankel classification system was compared at 72 hours postinjury to the 1-year follow-up examination. Fifty of 62 patients with complete injury at 72 hours were unchanged at 1 year. Five of these 62 patients had developed motor useful function in the legs or became ambulatory by 1 year, but all had sustained serious head injuries at the time of their trauma making initial neurological assessment unreliable. Ten percent of all cases had combined head injury impairing consciousness. Among 103 cognitively intact patients, none with complete injury at 72 hours were walking at 1 year. Of patients with sensory incomplete functions at 72 hours postinjury, 47% were walking at 1 year; 87% of patients with motor incomplete function at 72 hours postinjury were walking at 1 year. Spinal surgery during the first 4 weeks postinjury did not improve neurological recovery. A method of analyzing neurological and functional outcomes of spinal cork injury is presented in order to more accurately evaluate the results of future treatment protocols for acute spinal injury.

The first case of traumatic locked-in syndrome caused by direct damage to the brainstem a n d not by vascular OCclusion of the basilar artery is presented. The lesion consisted of cavitary necrosis of the ventral pontomedullary junction and bilateral disruption of t h e sixth cranial nerves. Other regions of brainstem damage are described and correlated with the patient's neurological deficits. The damage is thought to be d u e primarily to mechanical stretching occurring d u r i n g sudden hyperextension injury.Britt RH, Herrick MK, Hamilton RD: Traumatic locked-in syndrome.Ann Neurol 1: [590][591][592] 1977 Plum and P o s n e r [ 11 described the "locked-in syndrome" in quadriplegic patients with bulbar and facial paralysis. Although these patients are paralyzed a n d may appear comatose, they are fully conscious and By the fifth day the patient responded to incoming information with eye blinks. An electroencephalogram performed six days after admission showed a normal sleep pattern without focal or paroxysmal changes.Three weeks following admission the patient's neurological examination showed that visual fields and acuity were normal. There were bilateral sixth nerve palsies. Pupils were equal and reactive to light. The patient had vertical nystagmus in the adducting eye on lateral gaze bilaterally. Spontaneous ocular bobbing was present. The ciliospinal reflex was absent. The fifth cranial nerve showed a trace corneal reflex on the left but no response on the right. Pinprick response was present bilaterally over the face. There was marked trismus of the rnasseter muscles with a trace of function on the left. Facial movement was weak bilaterally. The patient understood speech but was aphonic. A trace of trapezius movement was seen bilaterally. The tongue had minimal movement. Motor examination showed complete spastic tetraplegia. Sensory examination demonstrated a questionable left hemisensory deficit to pinprick. He did not recognize light touch, position changes, or vibratory stimuli in his extremities.During the patient's hospitalization his condition remained unchanged, but he died of tracheal hemorrhage from erosion through the innominate artery 14 weeks after the accident. Pathological ExaminationThere was no evidence of injury to t h e skull or spinal column. The arteries at the base of t h e brain were thin walled and patent.The major pathological changes were confined to t h e lower brainstem and are summarized in t h e Figure. Grossly, in the lower p o n s t h e r e was focal yellow discoloration of t h e right basis pontis a n d beginning cavitation of t h e corticospinal and corticobulbar tracts. In the u p p e r medulla the pyramids were completely destroyed. T h e r e was bilateral cavitation, more marked on the right, of t h e lateral aspects of the medulla dorsal to t h e inferior olives (Figure, D ) . The destructive change diminished caudally and disap-