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Biomedical subjects

G J Green

Publications and source records attributed to G J Green.

At least 37 records · Page 2Linked to original sources
PubMed1983

Retinal circulatory changes after scleral buckling procedures.

The noninvasive laser Doppler technique was used to study retinal circulatory characteristics in five patients who underwent uncomplicated scleral buckling procedures. In each patient, the systolic/diastolic variation of the red blood cell speed in the retinal arteries (flow pulsatility ratio) was lower in the eye that had received an intrascleral implant and an encircling band than in the fellow eye. In one patient, an increase in flow pulsatility ratio accompanied an increase in retinal blood flow after removal of the scleral buckling elements. In another patient, the flow pulsatility ratio in the eye that had received a solid implant and an encircling band was less than the ratio in the fellow eye that had received an absorbable implant alone. Our results indicated that reduced retinal blood flow may be common after scleral buckling procedures, and may be a significant factor in otherwise inexplicable postoperative complications.

Adult↗
PubMed1983

The pharmacodynamics and pharmacokinetics of conventional and long-acting propranolol in patients with moderate hypertension.

1 The effects on heart rate and blood pressure after single and multiple dosing (1 month) of a long acting formulation of propranolol 160 mg daily, and conventional propranolol, 80 mg twice daily, or 160 mg daily were compared in 11 moderately hypertensive subjects previously shown to respond to propranolol. 2 After acute dosing all three treatments produced significant reduction in blood pressure. After multiple dosing all three treatments maintained significant reductions in lying, standing and exercise heart rate and blood pressure throughout the 24 h. At 24 h, after multiple dosing, the fall in resting and standing systolic BP was significantly greater with LA propranolol than with conventional propranolol 80 mg twice daily or conventional propranolol 160 mg once daily (P at least less than 0.05). 3 The plasma propranolol concentration time curve after LA propranolol showed slowed absorption, and the area under the curve was significantly lower than after conventional propranolol (acute dosing; LA propranolol 160 mg 560 mg ml-1 h, conventional propranolol 80 mg twice daily 1135 mg ml-1 h, conventional propranolol 160 mg daily 1414 mg ml-1 h).

Adult↗
PubMed1983

Response of human retinal blood flow to light and dark.

The laser Doppler technique was used to measure alterations in retinal blood flow in human subjects under dark-adapted conditions compared to light-adapted conditions. Retinal blood flow increased 40 to 70% after the transition from light to dark. We show quantitatively that the measured increases in retinal blood flow provide the appropriate increases of available oxygen for the inner retinal tissue necessary to compensate for increased oxygen consumption in the dark by the photoreceptor-RPE complex. In addition, we show that measured increases or decreases in human retinal blood flow are quantitatively linked to two intrinsic characteristics of the rod photoreceptor: its metabolic response to known, graded light levels, and its rhodopsin-mediated wavelength-dependent light-absorption properties. We also discuss how light-activated blood flow changes may provide a physiologic test for the autoregulatory capacity of the retinal vasculature.

Adaptation, Physiological↗
PubMed1982

Laser Doppler measurements of the effect of panretinal photocoagulation on retinal blood flow.

The laser Doppler technique was used to measure the pulsatile characteristics of the retinal arterial blood flow in diabetic patients with severe retinopathy immediately before argon laser panretinal photocoagulation (PRP) and again one to two months after PRP. In each measurement the relative variation of the maximum red blood cell velocity, Vmax, in a major branch retinal artery was determined throughout the cardiac cycle. Flow pulsatility was defined as the ratio of Vmax at maximum systole to Vmax at minimum diastole. Following PRP, each eye showed a decrease in flow pulsatility as well as a decrease in retinal arterial and venous diameters. The measurements are consistent with an autoregulatory response of the retinal circulation to increased inner retinal oxygen concentration following PRP. Laser Doppler measurements may be a useful means of assessing the effectiveness of a particular PRP treatment.

Adult↗
PubMed1980

Ischemic optic neuropathy in chronic papilledema.

We evaluated the condition of a patient with chronic papilledema due to pseudotumor cerebri in whom a permanent, monocular, inferior, altitudinal, visual field defect suddenly developed. Clinical and fluorescein angiographic findings indicated that the loss of visual field was due to ischemic optic neuropathy. Ischemic optic neuropathy might occur in papilledema if the tissue pressure in the optic disc becomes sufficiently elevated to occlude the pressure-sensitive prelaminar arterioles.

Adult↗
PubMed1979

The mechanism of the clonidine-induced reduction in peripheral parasympathetic submaxillary salivation.

The mechanism of the clonidine induced reduction in submaxillary salivation evoked by electrical stimulation of the chorda tympani was investigated in anaesthetised cats. This effect of clonidine was found to be dose and frequency dependent. In addition to clonidine, tramazoline, also a preferential presynaptic alpha-adrenoceptor agonist, produced a reduction in electricallly evoked salivation. Methoxamine, noradrenaline and naphazoline, which are less potent presynaptic alpha-receptor agonists, caused increases in salivation. Phentolamine only partially antagonized the decrease in salivation produced by clonidine whereas it was virtually abolished by yohimbine. Clonidine increased salivation evoked by intra-arterial injections of carbachol. These findings suggest that clonidine reduces peripheral parasympathetically evoked submaxillary salivation by activation of presynaptic alpha-adrenoceptors which inhibit cholinergic transmission.

Adrenergic alpha-Agonists↗
PubMed1979

The effect of clonidine on centrally and peripherally evoked submaxillary salivation.

In anaesthetised cats, clonidine (10 microgram/kg, i.v.) produced a 60% reduction in submaxillary salivation induced by brain stem stimulation at 10 and 15 Hz and reductions of 35 and 15% in salivation evoked by chorda tympani nerve stimulation at 5 and 15 Hz respectively. Pretreatment with clonidine (20 microgram/kg/day, orally) for 28 days reduced peripherally evoked salivation by 45%. These results suggest that both central and peripheral mechanisms are involved in the diminished salivation produced by clonidine, and the reduction on peripheral stimulation may reflect the presence of presynaptic alpha-adrenoceptors inhibiting cholinergic transmission.

Animals↗
PubMed1979

Action of clonidine on centrally evoked salivation in anaesthetized cats.

1. Clonidine (4 microgram/kg) given intracisternally to anaesthetized cats inhibited brain stem-evoked parasympathetic submaxillary or parotid salivation by 62% at 5 Hz and 44% at 15 Hz. 2. The inhibitory action of clonidine on salivation was equally prevented by pretreatment with either intracisternal yohimbine (175 microgram/kg) or phentolamine (250 microgram/kg), used as preferential pre- and post-synaptic alpha-adrenoreceptor-blocking drugs respectively. 3. the inhibition of centrally evoked salivation by clonidine is due to an action on alpha-adrenoreceptors but no clear evidence was obtained to indicate whether these were located pre- or post-synaptically. This is in contrast to the preferential presynaptic action of clonidine in reducing peripheral parasympathetic nerve-evoked salivation.

Animals↗
PubMed1979

Rate of onset of hypotensive effect of oral labetalol.

1 Labetalol caused a fall in blood pressure within 2 h or oral doses of 100, 200 and 400 mg in six hypertensive patients. 2 This fall which was dose-related was maximal by 3 h and was sustained when the drug was given in doses of 100 mg 8 hourly, 200 mg 8 hourly and 400 mg 8 hourly. 3 This rapid fall in pressure when labetalol is given by mouth which contrasts to that seen on administration of pure beta-adrenoceptor blocking agents is a valuable therapeutic property.

Administration, Oral↗
PubMed1978

Familial intraocular malignant melanoma: a case report.

A family with histopathologically proven intraocular malignant melanoma involving two generations is reported. A member of third generation was likely involved by history. Intraocular malignant melanoma, its familial occurrence, its occurrence with multiple malignancies, and its relationship to multiple malignancies occurring in a family are discussed.

Adult↗
PubMed1977

Acquired cerebral dyschromatopsia.

Color blindness developed in five patients apparently because of lesions in the posterior portions of both cerebral hemispheres. Three of them also had symptoms of prosopagnosia. The lesions were neoplastic in two and vascular in three of the patients. It would appear that bilateral, inferior, occipital lobe lesions may be responsible both for acquired cerebral dyschromatopsia and prosopagnosia. Evidence from experimental investigations in primates suggests that the areas of the cerebral hemispheres analogous to those involved in these patients, may be specialized for the processing of colored stimuli.

Adult↗