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Biomedical subjects

R W Greene

Publications and source records attributed to R W Greene.

At least 73 records · Page 4Linked to original sources
PubMed1985

Actions of neurotransmitters on pontine medical reticular formation neurons of the cat.

The actions of several neurotransmitters were determined on 43 antidromically identified reticulospinal neurons and 72 unidentified neurons in the paraabducens reticular formation of the anesthetized cat. All neurons were excited by glutamate and aspartate, both of which caused brief, high-frequency responses. In 80% of the reticulospinal neurons glutamate was more potent than aspartate, whereas in 61% of the unidentified neurons aspartate was more potent. Glutamate responses were reversibly antagonized by curare applied by pressure injection. Fast inhibitory responses were obtained on all neurons tested to gamma-aminobutyric acid, glycine, and norepinephrine. Some neurons showed similarly fast inhibitory responses to acetylcholine and serotonin. Acetylcholine and serotonin both acted on most neurons, but approximately equal numbers of neurons showed a relatively fast inhibition, a relatively slow and long-lasting excitation, and a biphasic combination of inhibition and slow-excitation responses. The pattern of responses to acetylcholine and serotonin is consistent with a spatial separation of excitatory and inhibitory receptors on different portions of the cell, possibly reflecting different inputs that use the same transmitter but have effects of opposite electrical and functional polarity. Although complicated by the phenomenon of excitatory and inhibitory responses to the same transmitter, these results are compatible with the Hobson-McCarley model of generation of desynchronized sleep.

Acetylcholine↗
PubMed1984

Adenosine enhances afterhyperpolarization and accommodation in hippocampal pyramidal cells.

Adenosine added to the perfusion fluid of rat hippocampal slices at 10 mumol X l-1 enhanced long lasting afterhyperpolarizations after single action potentials, bursts of action potentials or calcium spikes. Accommodation of firing during a depolarizing pulse was potentiated. An increase in calcium dependent potassium conductance is likely to mediate these effects. Adenosine at 50 mumol X l-1 induced a hyperpolarization accompanied by a reduction in input resistance. The hyperpolarization could be reversed at -85 mV. In TTX and TTX-barium treated slices the amplitude of the slow spike was decreased. This may result from a shunting of inward current in the dendrites due to an adenosine induced increase in potassium conductance. It is suggested that adenosine reduces pre- and postsynaptic excitatory signals principally by enhancing one or more potassium conductances. This effect is a powerful means for modulation of neuronal excitability and synaptic efficacy and can explain the antiepileptic activity of adenosine.

Adenosine↗
PubMed1981

Urinary calculi associated with portosystemic shunts in six dogs.

Portosystemic shunts were diagnosed in 6 dogs with urinary calculi and signs of neurologic disease. Five of the dogs were initially examined because of neurologic signs, and 1 was seen because of urinary tract problems. The composition of the calculi was variable, but in all 13 episodes of calculi formation, the calculi contained an ammonium or uric acid component. One dog is being controlled under medical management; 4 of the dogs died, and 1 was euthanatized. The interpretation of pathogenesis was that decreased delivery of blood to the liver due to shunting or decreased liver function can potentially result in high blood concentrations of ammonia and uric acid, both of which are metabolic end products cleared by the kidneys; thus, the urinary tract would be an excellent environment for the precipitation of their salts.

Ammonia↗
PubMed1981

Brain stem afferents to the periabducens reticular formations (PARF) in the cat. An HRP study.

Six injections of HRP were placed in the periabducens reticular formation (PARF). Two were placed ventromedial to the caudal half of the abducens nucleus (VIn), two were placed further laterally and ventral to the rostral half of the nucleus, and two were placed rostral to the nucleus. Most injections in PARF produced cell labeling in the vestibular and perihypoglossal nuclei bilaterally and labeled cells in the reticularis gigantocellularis (Rgc) and reticularis pontis caudalis (Rpc) nuclei contralateral to the injection site. Few labeled neurons were found in the caudal part of the paramedian pontine reticular formation (PPRF). In the mesencephalon, bilateral but more numerous ipsilateral labeled cells were found in the medial mesodiencephalic region including the nuclei of Cajal, Darkschewitsch and the posterior commissure. Injections placed caudomedial to VIn resulted in a characteristic concentration of labeled cells in the ipsilateral nucleus cuneiformis and rostral half of the contralateral superior colliculus (SC). Injections placed rostral to VIn in PARF produced cell labeling in the nucleus campi Foreli. The results are related to physiological evidence which suggests that PARF is an important premotor center for coordination of oculomotor, head and body movements.

Abducens Nerve↗
PubMed1981

Biphasic responses to acetylcholine in mammalian reticulospinal neurons.

Acetylcholine (ACh) responses were elicited by ionophoresis from neurons, located in the medial pontine reticular formation, which were antidromically identified as having axons projecting in the reticulospinal tracts. Most neurons were silent at rest and could be caused to discharge at a regular, slow rate by a constant application of glutamate. ACh altered this slow rate of firing in 28 of 29 cells but showed three different patterns of effect: approximately one-third were excited, one-third were inhibited, and one-third showed biphasic inhibition-excitation. The ACh responses were not sensitive to atropine. These observations suggest that reticulospinal neurons have ACh receptors mediating both inhibition and excitation, perhaps located on different portions of the same neuron.

Acetylcholine↗
PubMed1979

Intravenous leiomyoma of the bladder in a cat.

An intravenous leiomyoma was diagnosed in a 5-year-old male cat that had a history of listlessness, dysuria, and hematuria. The cat has been clinically normal for 25 months after excision of the neoplasm.

Animals↗
PubMed1978

Features of cystic calculi in cats in a hospital population.

The case records of 131 cats undergoing surgery for cystic calculi at The Animal Medical Center during the period of June 1969 to January 1975 were reviewed. Data for 16 intact females, 63 spayed females, 14 intact males, and 38 castrated males were analyzed. The mean age of first occurrence was 4.9 years. Meaningful conclusions regarding breed predisposition could not be made. Phosphate calculi were the predominant (124/128 analyzed) type. Swab specimens were taken from the bladder wall at time of surgery in 86 cases; only 28 (32.8%) were positive for bacteria.

Age Factors↗
PubMed1977

Canine urolithiasis: retrospective analysis of 438 cases.

In a retrospective analysis of 438 cases of canine urolithiasis, a total of 561 urolithic episodes were found to have occurred in a 6 1/2-year period. The hospital incidence of urolithiasis during that period, defined as the proportion of dogs hospitalized with urolithiasis to the total number of dogs hospitalized, was 2.8%. The major chemical component of the calculus in 307 dogs was phosphate; in 95 dogs, cystine; in 21 dogs, urate; in 12 dogs, oxalate; and in 3 dogs, carbonate. The Miniature Schnauzer, Dachsund, Dalmatian, Pug, Bulldog, Welsh Corgi, Beagle, and Bassett Hound were breeds that had a significantly higher (P less than 0.05) incidence of calculi than did breeds of other dogs hospitalized. Predisposition for calculi, by sex, was not found. Most dogs with calculi were between 3 and 7 years old. Most calculi were radiopaque and were located in the bladder or in the bladder and urethra. Specimens for bacteriologic culture were obtained by catheterization or by swabbing of tissue at the surgical site. Of 259 specimens obtained, 181 were culture-positive. The most common organisms isolated were Staphylococcus spp, Escherichia coli, Proteus spp, Streptococcus spp, and Klebsiella spp. Most of the bacteria were sensitive to gentamicin, chloramphenicol, nitrofurantoin, cephalothin, and methanamine mandelate.

Age Factors↗
PubMed1977

Recurrence of canine urolithiasis.

A retrospective analysis of urolithiasis in the dog was done at the Animal Medical Center, New York, NY, and involved a review of case records from Jan 1, 1968, to June 30, 1974. The study involved a total of 438 dogs that had a total of 561 urolithic episodes. Of the 438 dogs, 111 had 155 known recurrences of calculi. The types of recurrent calculi were phosphate (54 dogs), cystine (45 dogs), urate (7 dogs), oxalate (3 dogs), and carbonate (2 dogs). Two-thirds of the recurrent cases involved only 2 episodes. One-half of the population was composed of mixed breeds, Schnauzers, and Poodles. With the exception of 25 females that had phosphate calculi, all of the dogs with recurrences were males. Sixty-six dogs were tested for urinary bacteria and of these dogs, 40 had infected urinary tracts. The infected dogs had both phosphate and cystine calculi. In addition, most dogs with phosphate calculi had Staphylococcus infections, whereas the cultures from the dogs with cystine calculi had a wide range of bacteria.

Age Factors↗