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Biomedical subjects

J L Davis

Publications and source records attributed to J L Davis.

At least 181 records · Page 10Linked to original sources
PubMed1981

Effect of sulfonylurea therapy and plasma glucose levels on hemoglobin A1c in type II diabetes mellitus.

It is well known that hemoglobin A1c reflects plasma glucose concentrations in patients with diabetes mellitus. To examine hemoglobin A1c and plasma glucose relationships in sulfonylurea-treated patients, 25 patients with well-controlled type II diabetes (fasting plasma glucose 128 +/- 6 mg/dl, hemoglobin A1c 7.6 +/- 0.5 percent) were evaluated in a double-blind study. This study was divided into two phases (periods I and II). During period I each patient was given a diet plus a placebo and was followed every two weeks until the mean of two consecutive plasma glucose determinations was more than 50 mg/dl above the initial plasma glucose concentration obtained while the patient was taking sulfonylurea. At that point each patient was switched in a double-blind fashion to either diet plus a placebo or diet plus tolazamide. Fasting plasma glucose concentrations increased to 178 +/- 9 mg/dl (p less than 0.005) for all patients by week 2 of period I. The increase in hemoglobin A1c concentration was seen to lag behind the increasing fasting plasma glucose concentration by four to six weeks. Fasting plasma glucose and hemoglobin A1c concentrations returned to values indistinguishable from initial values in patients who were given tolazamide and who responded to it. A positive correlation was noted when the hemoglobin A1c concentration was compared with the fasting plasma glucose concentration measured four to six weeks previously.

Adult↗
PubMed1981

Anterior mediastinal tracheostomy with a pectoralis major musculocutaneous flap.

We suggest the pectoralis major musculocutaneous flap is a simple and reliable technique in constructing a mediastinal tracheostomy. It has the advantage of excellent vascularity and reliability even in those patients who have undergone preoperative radiation therapy. In addition, a well-vascularized lobe of thyroid tissue placed over the pharyngogastric anastomosis may decrease anastomotic leaks.

Carcinoma, Squamous Cell↗
PubMed1981

L-Proline inhibition of glutamate release.

The influence of 1 mM-L-proline on electrically stimulated release of endogenous glutamate from slices of rat frontal cortex was measured. One mM-L-proline approximates the in vitro concentration that inhibits glutamate-induced spreading depression. Also, this L-proline level has been reported to be present in brain after an intraperitoneal injection that induced amnesia in chicks. L-Proline but not D-proline exhibits an inhibitory effect on glutamate release, thus supporting the suggestion that this mechanism may play a role in memory retention and/or formation.

Animals↗
PubMed1980

Early experience facilitates the development of temperature regulation in the cat.

Thirty kittens were given a 30-min exposure to a moderately cool environment and drop in body temperature was measured. One group was tested every day from age 2 days to 21 days of age. A 2nd group was tested on Days 6-21 and a 3rd group tested only at 19 days of age. The 1st group (tested on Days 2-21) became homeothermic at an earlier age than did the other groups. The data are interpreted to indicate that early exposure to cool temperatures facilitates acquisition of temperature regulation in the cat, and that observed deficits in passive avoidance learning in young cats are not due to increased motor activity produced by a fall in body temperature.

Animals↗
PubMed1980

Amnestic potency of proline analogs correlates with anti-spreading depression potency.

L-Proline and some of its analogs have been shown to prevent spreading depression (SD) in the chick retina at relatively low concentrations and to impair memory processing without provoking toxic or electrophysiological disturbances. Both effects are hypothesized to be caused by inhibition of the effects of glutamate released into the extracellular space. L-Proline, its D-enantiomer, six proline analogs including two homologs (L-azetidine-2-carboxylic acid and DL-pipecolic acid), and five other compounds were examined for their effects on spreading depression and their amnestic and electrophysiological effects. L-Proline, L-baikiain, DL-3,4-dehydroproline, and L-4-hydroxyproline all reduced the incidence of SD in the chick retina and proved to be amnestic. D-Proline, L-pyroglutamic acid, L-azetidine-2-carboxylic acid, DL-pipecolic acid, L-glutamic acid diethylester, L-isoleucine and L-norleucine neither depressed SD nor caused retrograde amnesia. L-Prolyl-L-proline and L-glutamine did not depress SD at low concentrations but had significant amnestic effects. None of the listed compounds induced EEG disturbances. Implications for memory mechanisms are discussed in the light of these results.

Amnesia↗
PubMed1979

Studies of the electron-nuclear coupling between Fe(III) and 14N in cytochrome P-450 and in a series of low spin heme compounds.

We have observed the nuclear modulation pattern in the envelope of electron spin echoes for various low spin paramagnetic heme proteins including cytochrome c, myoglobin hydroxide, myoglobin mercaptoethanol, and cytochrome P-450, using the three-pulse-stimulated echo method. We have also carried out similar experiments with model compounds containing either [14N]- or [15N]imidazole. In many of the compounds studied, we have been able to identify the nuclear modulation effects arising from 14N of the porphyrin ring and have been able to characterize and interpret the modulation effects due to 14N of various nitrogenous axial ligands. We have found that the heme of low spin ferric cytochrome P-450 is coordinated to a nitrogenous ligand, probably imidazole. We have also demonstrated that the remote 14N of the imidazole ligand in a [14N]imidazole-heme-NO-model compound is coupled differently than in myoglobin nitroxide, demonstrating the direct effect of the protein of metal ligand bonding.

Binding Sites↗
PubMed1979

Interaction of bovine platelets with bovine glomerular basement membrane.

The interaction of bovine platelets with bovine glomerular basement membrane has been studied by aggregometry, transmission and scanning electron microscopy and measurement of [3H] serotonin release. In the absence of added calcium platelets adhere to basement membrane but fail to undergo the release reaction or aggregation. In the presence of 0.2-0.5 mM calcium release of serotonin and complete aggregation of the platelets are observed when sufficient basement membrane is present. Platelets were strongly adhered to the basement membrane surface, the platelet surface in the aggregates closely following the surface of the basement membrane. Platelet morphology in aggregates with basement membrane closely resembled that of platelets from collagen-induced aggregates. Basement membrane differed from collagen in its requirement for calcium for the aggregation and release reactions. In addition purified basement membrane was 1.5-3 fold less active on a weight basis than bovine tendon collagen in promoting aggregation.

Animals↗
PubMed1979

Memory enhancement induced in chicks by anesthetic doses of chlorpromazine.

Three experiments describe retroactive memory enhancement in chicks by chlorpromazine (CPZ), a potent membrane stabilizer at anesthetic doses. First, chicks trained on a one-trial peck suppression task under moderate aversant conditions and given 60--144 mg CPZ/kg, intraperitoneally, displayed increased memory retention 24 h later when compared with chicks given saline or 15--36 mg CPZ/kg. The second experiment confirmed the memory enhancement using a different moderate aversant on a different peck target and extended the effect to 48 h. The third experiment demonstrated the CPZ effect to be retrograde because the enhancement observed when CPZ was injected 1 min or 3 min after training did not occur when injection was delayed 4 h. One speculative interpretation of retrograde enhancement with CPZ includes the stabilization of swollen dendritic spines, which may facilitate neuronal pathways.

Anesthesia↗
PubMed1979

Retrograde amnesia in chicks and mice induced by 3,4-dehydro-DL-proline, a proline analog.

L-proline induces retroactive amnesia without causing brain seizures or isoelectric activity. 3,4-dehydro-DL-proline, a proline analog containing a double-bond in the 5-membered ring, has similar effects at a smaller dose. Three experiments describe the amnestic qualities of 3,4-dehydro-DL-proline in a chick memory paradigm, the retrograde quality of this amnesia, and its existence in a mammalian (mouse) preparation. Finally, EEG records show that chicks injected with amnestic doses of 3,4-dehydro-DL-proline do not exhibit seizure spiking or abnormal electrical activity.

Amnesia↗