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Biomedical subjects

B A Weissman

Publications and source records attributed to B A Weissman.

At least 127 records · Page 7Linked to original sources
PubMed1981

New analgesic drugs derived from phencyclidine.

Several esters of 1-(1-phenylcyclohexyl)-4-piperidinol (3), 1-(1-phenylcyclohexyl)-4-phenyl-4-piperidinol (10) and its propionate (11), and 1-(1-phenylcyclohexyl)-4-phenylpiperidine (13) were prepared and characterized. The new compounds, which are derived from phencyclidine, exerted analgesic activity in mice. The most potent is 10, which is twice as active as morphine. The antinociceptive activity of 10, 11, and 13 could be well correlated with their potency in the mouse vas deferens bioassay, and both were completely reversed by naloxone.

Analgesics↗
PubMed1981

Effective powers of flexible contact lenses.

Predictions of effective powers of flexible contact lenses including tear lenses, or assuming alignment, are compared with actual equivalent sphere effective powers of 12 low-minus and 2 high-plus lenses. The assumption of a tear lens improves accuracy of prediction.

Contact Lenses, Hydrophilic↗
PubMed1981

In vivo aqueous humor oxygen tension--as estimated from measurements on bare stroma.

Aqueous humor oxygen tension of the in vivo rabbit eye was estimated by a relatively atraumatic procedure. The anterior corneal surface of the eye was first scraped free of its epithelial layer. A polarographic oxygen electrode was then used to measure the oxygen tension at the bare stromal surface. Aqueous humor oxygen tension can be estimated from this measured steady-state stromal surface oxygen tension by correcting the measured oxygen tension for the tension drop across the stroma and endothelium. When animals breathed room air (155 mm Hg oxygen tension), the oxygen tension of the aqueous humor was 13 mm Hg; this rose to 150 mm Hg when the inspired oxygen tension was 713 mm Hg.

Animals↗
PubMed1981

Diffusion of oxygen in human corneas in vivo.

No oxygen was detected on the corneal surface of human subjects breathing air or almost pure oxygen. These results suggest that the epithelium obtains all its oxygen fro the air or the palpebral conjunctiva and that the endothelium is supplied with oxygen solely by the aqueous humor.

Adult↗
PubMed1980

Long-term interactions between endogenous and exogenous opiates.

The in vitro biological effect of various opiates was studied in the guinea pig ileum bioassay. Besides their direct, immediate effect, certain opiates induced sensitivity changes which persisted after their removal and the complete recovery of the preparation. These specific, asymmetrical interactions may represent long-term modulation of the opiate receptor. The in vivo pharmacological implication of opiate interaction is discussed.

Animals↗
PubMed1980

Power and tear volume exchanges with flexible contact lenses.

Mathematical formulas are used to infer volumetric tear exchange from power changes of flexible contact lenses in situ. These calculations are developed from changes along the radius, and must be considered approximate due to several underlying assumptions.

Contact Lenses, Hydrophilic↗
PubMed1980

Oxygen tension under a permeable contact lens with and without tears.

Oxygen tensions were calculated under two different oxygen-permeable, flexible contact lenses (daily wear and extended wear) both with and without consideration of tear layers (but without tear exchange). Tear layers do not have significant effects on precorneal oxygen tension.

Contact Lenses, Hydrophilic↗
PubMed1980

Humoral endorphin in human body fluids during pregnancy.

The presence of an enkephalin-like substance ('humoral endorphin') in human maternal and cord blood, as well as in amniotic fluid, has been demonstrated in this study. Utilizing antibodies to leucine-enkephalin, it was found that the level of this substance in maternal and in cord blood remained stable during pregnancy whereas the concentration in amniotic fluid was significantly higher at mid-trimester than during labor at term.

Amniotic Fluid↗
PubMed1980

Characterization of humoral endorphin.

Utilizing a radioimmunoassay (RIA) with antibodies produced against leu-enkephalin, the presence of humoral endorphin in various body fluids and tissues has been shown. Pretreatment with trichloroacetic acid (TCA) was needed in all cases in order to detect the immunoreactivity. However, both treated and untreated samples of humoral endorphin were active in the opiate receptor assay. Gel filtration on Bio-Gel P-2 as well as on Sephadex G-10 columns of human cerebrospinal fluid (CSF), amniotic fluid (AF) and blood shows that they all contain a similar material with an apparent molecular weight of 1,000-1,400 daltons. Chromatography of rat brain homogenate exhibited two peaks of immunoreactivity, one of which is probably due to enkephalins and the other to humoral endorphin. The latter fraction was found to be very stable when incubated in CSF, while its degradation in blood was slightly faster. This opioid compound inhibited the electrically stimulated contractions of the guinea pig ileum; the specificity of this action was indicated by its reversal with low concentrations of naloxone. In pregnant women, humoral endorphin levels in maternal and cord blood remains stable during pregnancy, while there is a significantly higher concentration of humoral endorphin in the amniotic fluid at mid-trimester as compared to that in term pregnancies during labor.

Amniotic Fluid↗
PubMed1980

Humoral endorphin: can in vitro experiments explain in vivo results?

Humoral endorphin, an endogenous substance isolated from brain, blood and cerebrospinal fluid, reveals non-conventional interactions with both opiate agonist (morphine) and antagonist (naloxone) in the guinea pig ileum bioassay. The opioid activity of humoral endorphin is potentiated by pretreatment of the preparation with morphine and vice versa. Naloxone, a specific opiate antagonist, interacts with humoral endorphin in a distinct manner which distinguishes it from opiates: while low concentrations of naloxone antagonize the effect of humoral endorphin, high concentrations of the antagonist are less effective and even potentiate its opiate activity. These interactions between opiate agents can be explained assuming conformational transformation of the opiate receptor. The in vitro interactions shed new light on paradoxical and conflicting results of in vivo experiments and indicate the physiological function of humoral endorphin.

Animals↗
PubMed1979

Enkephalin levels in rat brain after various regimens of morphine administration.

Rats implanted with a single morphine pellet for a short period of 72 h have been shown to have a lower concentration of enkephalin in the brain, as determined by a radioimmunoassay (RIA) detecting Leu- and Met-enkephalin as well as another endogenous substance. Two other paradigms of morphine implantations did not cause any change in enkephalin levels. Various protocols of morphine injections failed to elicit changes in enkephalin content in the rat brain. The significant decrease observed after the short regimen implantation suggests that at a certain stage in the development of physical dependence a reduction in the amount of enkephalin occurs, but returns to normal values within a short period.

Animals↗
PubMed1979

Changes in back radius of soft contact lenses when flexed.

Mathematical statements are made for the various hypotheses describing the change in radius of curvature of the back surface of a flexible contact lens as it flexes. These hypotheses may now be tested for validity in predicting both optical and physiological behavior of real contact lenses in situ.

Contact Lenses, Hydrophilic↗
PubMed1979

Approximate tear volumes under flexible contact lenses.

The quantification of tear volume trapped under a flexible contact lens in situ is important for an understanding of both optical and physiological lens behavior. Mathematical treatment is used to calculate the flexed back radii of flexible contact lenses in situ from the various hypotheses available. For each hypothetical radius the tear volume under the lens is calculated. The method is limited in accuracy due to several underlying assumptions. Twelve lens situations are analyzed, and the results indicate a tear volume of the order of 10 microliters.

Contact Lenses, Hydrophilic↗