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Biomedical subjects

E B Davis

Publications and source records attributed to E B Davis.

At least 37 records · Page 2Linked to original sources
PubMed1992

Effects of cholinergic and adrenergic agonists on adenylate cyclase activity of retinal microvascular pericytes in culture.

Pericytes are contractile cells that might help regulate microvascular blood flow. To understand their potential role in the regulatory responses of the retina and optic nerve head vessels, the response of pericytes isolated from bovine retinal microvessels was determined to oxotremorine, isoproterenol, phenylephrine, and clonidine. Isoproterenol doubled the basal levels of cyclic adenosine monophosphate (cAMP) specifically through beta-adrenergic receptors, because the effect was blocked by dl-propranolol. The alpha 1 agonist phenylephrine did not induce any major change in adenylate cyclase activity. The alpha 2 agonist clonidine decreased basal cAMP synthesis and reduced the effect of isoproterenol. The cholinergic agonist oxotremorine did not modify the basal activity of adenylate cyclase but was able to decrease by almost 50% the forskolin-induced increase of cAMP. These results suggest that pericytes have functional adrenergic and cholinergic receptors, and they might respond to autonomic vasoactive substances present in vivo.

Adenylyl Cyclases↗
PubMed1991

Angiotensin II binding receptors in retinal and optic nerve head blood vessels. An autoradiographic approach.

Angiotensin II (AII) binding sites were identified in cross-sections of the cat retinal and optic nerve vasculatures. The authors used 3H-AII and 125I-saralasin, an agonist and a high-affinity antagonist of AII receptors, respectively, to generate light microscopy autoradiograms in resin-embedded tissues. With both radioligands the presence of AII binding sites was confirmed in retinal arterioles but not in the veins or capillaries of the retina. Additionally the presence of such binding sites in the capillaries of the optic nerve head was shown. These results support the hypothesis that microvascular tone and perhaps autoregulatory responses of optic nerve capillaries might be influenced by vasoactive substances, such as AII, either leaking from the choroid or locally synthetized.

Angiotensin II↗
PubMed1990

Response of retinal vasculature to phenylephrine.

In a freshly enucleated bovine eye, the retinal arteries and veins constrict when phenylephrine is applied directly on the surface of the vessel walls. This "in situ" preparation allowed us to observe the reaction of retinal vessels without any surgical procedure that might alter the vascular response to agonists. These results indicate that alpha1-adrenergic receptors are present in the retinal vessels, which might therefore respond to vasoactive hormones. If, when, and how these reactions occur is still to be studied.

Animals↗
PubMed1989

Perinatal and first year follow-up of patients with Prader-Willi syndrome: normal size of hands and feet.

Four patients with Prader-Willi syndrome, diagnosed in the neonatal period and followed during the first year of life, are reported. There were three males and one female. All four patients presented with hypotonia and distinct craniofacial dysmorphism. Prometaphase chromosome analysis showed interstitial deletion of 15q in all of them. The placentae and umbilical cords were examined in three of the patients and found normal. Electromyography done in the neonatal period suggested primary myopathy. Height, weight and head circumference were normal at birth in all patients. Hand and foot measurements showed normal size at birth and during the first year of life.

Anthropometry↗
PubMed1989

Biochemical evidence for cholinergic activity in retinal blood vessels.

Blood vessels from human, cat, pig and bovine retinas were analyzed for their contents of choline acetyltransferase (ChAT) and muscarinic binding sites. ChAT was measured by the synthesis of 3H-acetylcholine in the presence of 3H-acetyl CoA and choline. Muscarinic binding sites were determined by the specific binding of 3H-quinuclidinyl benzylate (3H-QNB). Tissue levels of ChAT varied from 39-850 nmol/g/hr, the lowest values being in human tissues. Muscarinic binding sites were less different (0.5 to 1.8 fmol/mg net weight) among the species studied, being the highest values in human retinal vessels. It appears that retinal blood vessels not only have sites to bind acetylcholine, perhaps to mediate physiologic responses, but might be capable of supplying acetylcholine for local vascular tone control.

Animals↗
PubMed1988

Angiotensin-converting enzyme in bovine, feline, and human ocular tissues.

Angiotensin-converting enzyme was shown to be present in retinal vessels and neural retina of feline, bovine, and human eyes. It was also demonstrated in the other ocular tissues of feline eyes, in especially high concentration in the highly vascular uveal layer. Its role in the physiology of ocular blood flow and neurophysiology is uncertain, especially in the retina where circulating angiotensin and bradykinin are confined to the intravascular space by the blood-retina barrier, and sufficient data are not available to describe these peptides as transmitters or modulator molecules in the retina.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1987

The response of retinal vasculature to angiotensin.

A retinal arterial constriction was produced in anesthetized cats with a continuous transvitreal infusion of angiotensin I or angiotensin II (Ile-5). Constriction of vessels near the infusion cannula tip occurred over a range of angiotensin II concentrations from 10(-9) to 10(-4) molar, and was reversibly blocked by a ten-fold excess of the competitive antagonist saralasin. Constriction did not occur in response to angiotensin I if angiotensin-converting enzyme was blocked with Captopril. Control infusions of saline did not elicit a contraction of the retinal arteries. Severe axonal and inner retinal damage and necrosis occurred when angiotensin II produced a prolonged vasospasm, but not after infusion with control solutions, or when-constriction caused by angiotensin was brief.

Angiotensin I↗
PubMed1987

Angiotensin binding sites in bovine and human retinal blood vessels.

Blood vessels isolated from bovine and human retinas have sites that specifically bind 3H-angiotensin II (3H-Ag II) with an apparent dissociation constant (Kd) of 14 nM and a capacity of binding (Bmax) of 0.82 pmol/g. The binding sites for 3H-Ag II appear to be influenced by guanine nucleotides (GTP) and cations (Mg2+ and Na+) in a way that resembles angiotensin II receptors in other tissues. The physiologic effect of blood-borne or locally-formed angiotensin II on retinal blood flow remains to be defined.

Angiotensin II↗
PubMed1985

A clinical, fluorescein angiographic, and electron microscopic correlation of cystoid macular edema.

Electron microscopic findings in an eye removed from a woman who had biomicroscopic and angiographic signs of cystoid macular edema occurring in association with a peripheral choroidal melanoma disclosed evidence that the anatomic basis for the biomicroscopic and angiographic changes was the polycystic expansion of the extravascular compartment of the retina by serous exudate and not, as previously reported, edema of the Mueller's cells.

Aged↗
PubMed1985

Creating smaller eyedrops by reducing eyedropper tip dimensions.

The risk of toxicity and adverse systemic effects from eyedrops is increased because of the large size of conventional eyedrops. Although the tear film normally contains only 7 to 10 microliters, commercial eyedrops are 50 to 70 microliters. Much of the excess is pumped into the nasolacrimal system where it is systemically absorbed and capable of causing toxicity. A smaller eyedrop can achieve a maximal tear film concentration with far less systemic absorption. We found that changes in the outer and inner diameters of an eyedropper tip can alter eyedrop volume markedly. By selecting appropriate tip dimensions we produced eyedrops of less than 25 microliters; in some cases they were as small as 11 microliters.

Administration, Topical↗
PubMed1984

Outcomes of care systems for chronic patients.

In a study of the postdischarge treatment of 119 comparable chronic schizophrenics hospitalized and treated after release in six community mental health care systems, it was found that lower rehospitalization rates and longer community survivorship correlated significantly with patients' compliance in early postdischarge treatment plans and the frequency of aftercare visits prescribed for them during the early postrelease period. Rehospitalization rates and community survivorship experience were substantially better for patients of two of the six systems, without disproportionate reduction of their clinical or social functioning in the community. Characteristics of the community care systems with better outcomes are described.

Adolescent↗
PubMed1980

Modified goniotomy for inflammatory glaucoma. Histologic evidence for the mechanism of pressure reduction.

A modified goniotomy (trabeculodialysis) was performed on both eyes of a 33-year-old woman who had glaucoma secondary to sarcoid uveitis. One month after trabeculodialysis, a cataract extraction was performed on one eye and a histologic specimen was obtained from the area of the filtration angle that was previously incised. Successful control of intraocular pressure has been maintained in both eyes for 18 months following trabeculodialysis. By light and electron microscopic examination, there was a nonhealed incision between the anterior chamber and Schlemm's canal. Trabeculodialysis, it is concluded, works by providing direct communication between the anterior chamber and Schlemm's canal, and might be effective in all trabecular obstructive glaucoma of short duration before secondary changes occur in the outer drainage channels.

Acetazolamide↗
PubMed1979

Mental illness in blacks: an overview, and treatment approaches.

Provisions for inner city mental health services must recognize the association between poverty, discrimination, and related social and physical conditions and disproportionately high rates of severe mental disorder-a transcultural phenomenon.Program emphasis should therefore be on the prevention, early recognition, prompt and effective treatment and rehabilitative care of psychosis. The total spectrum of psychiatric services is required for this, and thus an opportunity is afforded for necessary training and research.Poverty has negative impact on general health and cognitive development as well as on self-esteem, self-care, and the ability to utilize medical and health services. This contributes to a vicious, intergenerational poverty cycle.Primary prevention of mental illness, where possible, depends at present on socioeconomic change. Secondary prevention, ie, timely, appropriate treatment, is effective, but requires patient access to and acceptance of all indicated modalities of care.

Black or African American↗
PubMed1978

Herpes simplex retinitis.

Fatal encephalitis with accompanying retinitis developed in a previously healthy 18-month-old infant. Clinically the disease appeared as whitish-yellow punctate lesions, perivascular cuffing, and hemorrhage. The antibody titer to herpes simplex rose from 1:8 on the day of admission to 1:256 on the day of death. Postmortem, intranuclear inclusion bodies that were typical of those found with herpesvirus were seen in the brain and retina. Viral particles consistent with those of herpesvirus were found by electron microscopy in the brain and in the inner-nuclear and ganglion-nerve fiber layers of the retina. This demonstrates the direct infectious nature of herpetic retinitis. Hematogenous spread of the virus to the retina is presumed.

Brain Stem↗
PubMed1978

The decision to hospitalize.

The authors explored determinants of psychiatric hospitalization in four Manhattan general hospital emergency rooms and found that although the nature and severity of a patient's problem played the most important role in the decision to hospitalize, the facility involved was also a determining factor. The findings are discussed in relation to policy concerning staffing and organization of emergency room services and future studies of service delivery in this area.

Adult↗