Electron microscopic study of monkey retina after photodynamic treatment

The purpose of this histological study was to determine the effects of photodynamic treatment, using a hematoporphyrin derivative and argon laser, on normal retinas of monkeys. Ten cynomolgus monkeys were treated with a hematoporphyrin derivative, given intravenously at a dose of 2.5 mg/kg. Forty minutes or 1 or 3 days after the injection, argon laser photoradiation was given over a 2.0-mm-diameter with a 10-min exposure and at an intensity of 40, 100, or 200 mW. The eyes were enucleated 1, 3, 4, 15, 18, 21, 35, or 38 days after the photoradiation and tissue samples were observed under a transmission electron microscope. The most fragile regions in the retina were the retinal nerve fibers, the outer segments of the visual cells, and the retinal pigment epithelium. Vascular endothelial cells were also fragile. The retinal capillary was easily obstructed, and the choriocapillaris was also occluded in an animal with severe retinal damage. The Mueller cells had the highest tolerance to the photodynamic treatment. Thus, exposing the normal part of the retina to light during photodynamic therapy should be avoided.     

IMMUNODEFICIENCY-MALIGNANCY ASSOCIATION AT AUTOPSY IN JAPAN

This paper referred to primary Immunodeficiency diseases (PID)-malignancy association in autopsy cases in Japan. The occurrence of malignant neoplasms almost centered upon ataxia-telangiectasia among PID in Japan. It seems to be due to extremely shorter life span in Japanese patients with PID except for in those with ataxia-telangiectasia, compared with that in European and American patients. Most of the malignant neoplasms seen in Japanese patients with PID were epithelial and were seen mostly in older patients, while lymphoreticular tumors were rare. Gastric cancer was the most frequent of the epithelial tumors.     

Effect of histamine and substance P on the rabbit and human iris sphincter muscle

Background and methods: In an attempt to clarify the functional action of histamine and substance P on atropine-resistant miosis, we isolated rabbit and human iris sphincter muscles and investigated their mechanical properties using the isometric tension recording method. Results: Substance P dose-dependently contracted the rabbit iris sphincter, but had no effect on the human iris sphincter. In the rabbit iris sphincter, histamine reduced the amplitude of twitch contraction evoked by field stimulation but had no effect on carbachol-induced contraction. Thioperamide, but not mepyramine or cimetidine, partially antagonized the histamine-induced reduction in the amplitude of twitch contractions. In the human iris sphincter, on the other hand, histamine dose-dependently provoked contraction and the amplitude of histamine-induced contraction was affected neither by atropine nor by indomethacin. Conclusions: These results provide evidence that histamine has strong contractile effect on the human iris sphincter muscle; the rabbit iris sphincter muscle, however, apparently lacks functional histamine receptors. In rabbits, exogenously applied histamine only activates H₃ receptors located on the cholinergic nerve terminal, hence the excitatory neuro-effector transmission is suppressed. Thus, histamine may have an important roles in atropine-resistant miosis in humans, but not in rabbits.     

Ketotic hypoglycemia in patients with allergic diseases

BACKGROUND: Ketotic hypoglycemia is the most common cause of recurrent hypoglycemia in early childhood but its etiology is poorly understood. Elimination diets have been used for the prevention or treatment of some allergic diseases; however, these diets entail a risk to the normal nutrition and growth of children. The present study investigated whether elimination diets are related to the occurrence of ketotic hypoglycemia. METHODS: The prevalence of allergy treated with elimination diet therapy was retrospectively investigated in 18 patients with ketotic hypoglycemia seen in Yamaguchi University Hospital between January 1995 and September 1999. Data were gathered by reviewing the patients' medical charts. RESULTS: Ten (55.6%) of 18 patients with ketotic hypoglycemia had allergic diseases. Six (60%) of the patients had been treated with strict elimination diets and the others were on incomplete elimination diets for the prevention of allergy. The ketotic hypoglycemia patients with allergic diseases had experienced fewer pre-existing infectious diseases than those without allergic diseases. CONCLUSIONS: Patients with allergic diseases treated with elimination diets have a relatively high tendency towards developing ketotic hypoglycemia. They might have a lower capacity to tolerate fasting due to their excessive avoidance of many foods, even during periods when they are not undergoing strict elimination diets.     

Pre-synaptic actions of noradrenaline on the dog ciliary muscle tissue

Effects of noradrenaline (NA) on the electrical and mechanical properties of the dog ciliary muscle were investigated using microelectrode- and isometric tension recording methods. Electrical-field stimulation to the tissue evoked excitatory junctional potentials (e.j.ps) followed by twitch contractions. Both responses were abolished by tetrodotoxin (TTX, 10(-7) M) or atropine (10(-6) M), thereby indicating that these responses are cholinergic-related. Exogenously applied NA (greater than 10(-8) M) suppressed the amplitude of e.j.ps and the following twitch contraction evoked by field stimulations, with no change in the resting tension, membrane potential and input membrane resistance of the smooth muscle cells. Exogenously applied carbachol dose-dependently contracted the ciliary muscle. However, NA (10(-5) M) did not affect the carbachol-induced contraction, thereby indicating that NA acts on the nerve terminals and reduces the amount of transmitter released from the terminals. Inhibitory effects of NA on the twitch contraction were antagonized by yohimbine (10(-6) M), but not by prazosin (10(-6) M) or timolol (10(-6) M). Guanethidine (5 X 10(-6) M) had no effect on the contraction evoked by field stimulation. These results provide evidence that exogenously applied NA activates the alpha 2-adrenoceptor located on cholinergic nerve terminal, hence the excitatory neuro-effector transmission is suppressed. These actions may explain the decrease in near point of accommodation observed with clinical application of adrenergic agents.