Search PubMed⌕ Search

Biomedical subjects

D D Johnson

Publications and source records attributed to D D Johnson.

At least 109 records · Page 6Linked to original sources
PubMed1984

Cyclic nucleotides and seizures in a hereditary model of epilepsy.

The high seizure susceptibility in epileptic fowl is due to an autosomal recessive mutation. Cyclic AMP and cyclic GMP concentrations were determined in brains from two day old epileptic chicks (homozygotes) during an inter-ictal period as well as during and following a seizure evoked by stroboscopic stimulation. The data were compared to values obtained from non-epileptic carrier chicks (heterozygotes) sacrificed in an unstimulated state or subjected to the seizure evoking stimulus. During the inter-ictal state in epileptics no abnormalities were found in cyclic nucleotide concentrations indicating that the high seizure susceptibility is not related to abnormalities of these nucleotides. Although seizure activity in epileptics was associated with reduced cyclic AMP in the optic lobes this also occurred in carrier chicks subjected to the seizure evoking stimulus. The only significant changes in cyclic GMP levels, occurring as a result of seizures in epileptics, were an increase in cyclic GMP in the cerebral hemispheres during the seizure and a decrease in the optic lobes during the postictal period.

Animals↗
PubMed1984

Characteristics of the phagocytically induced respiratory burst in leukocytes from young adult and aged beagle dogs.

Phagocytically stimulated canine leukocyte suspensions obtained from 12 young adult and 43 aged individuals were examined for several physiological manifestations of the phagocytically induced respiratory burst. There was considerable variation in levels of oxygen consumption, glucose oxidation via the hexose monophosphate shunt (HMPS), and chemiluminescence response by both resting and phagocytically stimulated leukocytes from different individual animals in each age-group. Leukocyte suspensions from specific individuals in each age-group exhibited a weakly responsive respiratory burst. Chronological age could not be used as a predictor of either the specific (oxygen consumption and HMPS activity) or nonspecific (chemiluminescence response) manifestations of the respiratory burst. The kinetics of the chemiluminescence response were similar for all age-groups. Collectively, the results suggest that there is not an age-related alteration in the phagocytically induced respiratory burst of canine neutrophils and that cells from young adult and aged dogs have a comparable capacity to generate levels of highly reactive antimicrobial oxidizing agents. The increased relative susceptibility of aging dogs to microbial agents is apparently not related to an absent, abbreviated, or reduced leukocyte respiratory burst.

Aging↗
PubMed1984

Anticonvulsants in epileptic fowl.

The high seizure susceptibility in epileptic fowl is an autosomal recessive trait characterized in homozygotes by seizures that occur spontaneously and in response to photic stimulation or hyperthermia. Both of the latter stimuli can be used to evoke seizures in drug studies. Epileptic fowl have abnormal inter-ictal EEG activity. When exposed to photic stimulation spiking is apparent on the EEG at seizure onset. Phenobarbital, primidone, phenytoin, and valproic acid reduce seizure susceptibility at plasma concentrations approximating those used to control generalized and focal cortical tonic-clonic seizures in humans. Carbamazepine and the benzodiazepines also reduce seizure susceptibility. These data indicate that epileptic fowl provide a useful model for generalized and focal cortical tonic-clonic epilepsies. Ethosuximide was inactive in epileptic fowl. However, trimethadione had anticonvulsant activity indicating that this model is only relatively specific for the above seizure types. When seizures were evoked by hyperthermia phenobarbital but not phenytoin or valproate reduced seizure susceptibility. GABA (gamma-aminobutyric acid), AOAA (amino-oxyacetic acid) and THPO (4,5,6,7-tetrahydroisoxazolo[4,5-c] pyridin-3-ole, a glial specific inhibitor of GABA uptake) all have anticonvulsant activity against seizures evoked by photic stimulation in young chicks. These data indicate that this model may be particularly useful for studies of the anticonvulsant activity of compounds designed to enhance GABAergic transmission.

Animals↗
PubMed1983

Precocious in vitro development of satellite cells from dystrophic chicken muscle.

Satellite cells, liberated from pectoral muscle of juvenile dystrophic chickens by sequential treatment with collagenase, hyaluronidase, and trypsin and preplated to remove fibroblasts and cultured on gelatin proliferated rapidly, fused and formed confluent muscle cultures within 6 d in vitro with minimal contamination by fibroblasts. When identical isolation and culturing techniques were applied to muscle from age-matched normal chickens proliferation and differentiation were slower, contamination with fibroblasts was much greater, and only a small number of myotubes were formed. After injection of the myotoxic anesthetic marcaine into normal pectoral muscle for 5 consecutive days, myotube formation was accelerated in satellite cell cultures, but the rate of differentiation was not as rapid as that occurring in cells from dystrophic muscle.

Animals↗
PubMed1983

Anticonvulsant activity of the glial-selective GABA uptake inhibitor, THPO.

The intramuscular administration of 4,5,6,7-tetrahydroisoxazolo [4,5-c] pyridin-3-ol (THPO) delayed the onset of isonicotinic acid hydrazide-induced seizures in very young chicks but not in adult mice, the difference being due to the state of development of the blood-brain-barrier which controls access of the drug to the brain tissue. THPO was also effective in preventing seizures induced in epileptic chicks by intermittent photic stimulation. The anticonvulsant action after combined administration of THPO and gabaculine, an inhibitor of GABA-alpha-oxoglutarate aminotransferase activity, was no greater than the anticonvulsant action of gabaculine alone.

4-Aminobutyrate Transaminase↗
PubMed1983

Febrile seizures in epileptic chicks: the effects of phenobarbital, phenytoin and valproate.

Epileptic seizures can be evoked in chicks homozygous for the epileptic seizure gene (epi, epi) by elevating their body temperature using microwave diathermy. These seizures precede and differ in motor seizure pattern from a second clonic-tonic seizure produced by hyperthermia in both epileptic and carrier (heterozygote, Epi, epi) chicks. Hyperthermia did not evoke seizures in adult epileptic chickens. Phenobarbital delayed the onset of epileptiform seizures whereas phenytoin and valproate had no effect. These data suggest that epileptic chicks may provide a suitable model for studies on febrile convulsions.

Animals↗
PubMed1982

Plasma glucose and insulin responses to propionate in preruminating calves.

Eighteen preruminating calves obtained at approximately 38 d of age were used to determine whether the ruminant insulin response to propionate is an inherent response or one that is acquired because of ruminal propionate production. A liquid milk replacer diet was fed alone or with isocaloric additions of propionate [50 mmol . (kg BW . 75-1 . d-1] or glucose. Both additions caused a strong insulin response, but the response by propionate-fed calves appeared to be independent of plasma glucose concentrations during the early post-feeding hours. After receiving the experimental diets for 18 d, all calves were given an iv infusion or propionate [.035 mmol propionate . (kg BW . 75-1 . min-1 for 20 min]. All calves demonstrated a plasma insulin rise and glucose decline due to the infusions, but glucose-fed and propionate-fed calves appeared less sensitive to the iv propionate than the calves fed only milk replacer.

Age Factors↗
PubMed1981

The practice of coronary artery bypass surgery in 1980.

We obtained information from 677 cardiac surgeons in the United States on the type of practice, case load, and techniques currently used for coronary bypass operations. These surgeons collectively performed 93,000 bypass operations in 1979. Less than 25% of these procedures were done in university or federal hospitals; the majority were performed in the private sector by surgeons engaged in a single specialty group practice. The mean case load in 1979 was 137 operations per surgeon, and only 46 (6.8%) did fewer than 25 bypass operations during that year. These surgeons devote a relatively small percentage of their professional activity to other areas in thoracic surgery--the majority do not perform congenital heart surgery and two thirds devote less than 10% of their professional activity to general thoracic surgery. Compared with our previous national survey done in 1975, techniques used for bypass grafting have changed considerably over the past 5 years. An increasing number of surgeons conduct cardiopulmonary bypass with an arterial input line introduced into the ascending aorta and with a single cannula for venous drainage and do not routinely vent the left ventricle. Cold chemical cardioplegia has become the technique of choice (by 91% of surgeons) for myocardial protection, sequential bypass grafts are now widely employed, and 83.2% of surgeons perform all distal anastomoses during a single period of cardioplegic arrest.

Cardiac Surgical Procedures↗
PubMed1980

Reactive hypoglycemia.

The clinical characteristics and scores on the Minnesota Multiphasic Personality Inventory (MMPI) of 192 patients undergoing a five-hour oral glucose tolerance test (OGTT) for evaluation of reactive hypoglycemia were assessed. There were twice as many women as men. One hundred twenty-nine patients had spells of light-headedness, shakiness, diaphoresis, weakness, and fatigue. Hypoglycemic symptoms occurring during the test were not related to level of plasma glucose nadir or to rate of descent of glucose level. Hypoglycemia was not found when glucose levels were measured during occurrence of spontaneous symptoms in 86 patients. MMPI scores were significantly different from those of general medical patients. Both men and women evinced a conversion V profile. The five-hour OGTT seems unreliable for the diagnosis of reactive hypoglycemia, and most patients with symptoms suggestive of hypoglycemia may have emotional disturbances.

Adolescent↗