Soluble kit receptor in human serum

c-kit encodes the transmembrane receptor tyrosine kinase (Kit) for the recently described ligand stem cell factor (SCF). We have developed an enzyme-linked immunosorbent assay for measuring soluble human Kit and we have used the assay to show high levels of soluble Kit in human serum. The distribution of soluble Kit levels was investigated among 112 normal human serum donors. The mean serum level (+/- SD) was found to be 324 +/- 105 ng/mL with the values falling between 163 ng/mL and 788 ng/mL. No correlation between soluble Kit levels and the sexes or ages of the donors was found. Partial purification using immunoaffinity chromatography allowed us to characterize the soluble Kit from pooled human serum. Antibodies generated to a 497-amino acid recombinant human soluble Kit corresponding to the N-terminal extracellular domain of the receptor recognized the serum-derived soluble Kit by immunoblotting. We found that the serum-derived soluble Kit is glycosylated, with mostly N- linked but also O-linked carbohydrate, and with terminal sialic acid residues. When compared with the recombinant human soluble Kit, the serum-derived material was similar both in size and glycosylation pattern. CNBr cleavage of the isolated serum-derived material followed by amino terminal sequencing confirmed the presence of five peptides expected for the extracellular portion of the Kit molecule. The immunoaffinity purified serum-derived soluble Kit inhibited binding of [125I]SCF to membrane-bound receptor in an in vitro assay. These results indicate that soluble Kit could modulate the activity and functions of SCF in vivo.     

Adrenergic mechanisms in oxygen chemoreception in the cat aortic body

Sixteen cats were studied to test the hypothesis that oxygen chemoreception in the cat aortic body is dependent on the beta-adrenergic mechanism. The chemoreceptor activity was measured from a few aortic chemoreceptor afferents in each cat, anesthetized with alpha-chloralose (60 mg X kg-1). Three types of experiments were conducted. Aortic chemoreceptor responses to steady-state hypoxia (PaO2 range, 100-30 Torr) were measured (a) before and during intravenous infusion of the beta-receptor agonist, isoproterenol (0.5 micrograms X kg-1) in nine spontaneously breathing cats, and (b) before and after intravenous injection of the beta-receptor antagonist, propranolol (1 mg X kg-1) in seven cats which were paralyzed and artificially ventilated. In the third category (c) the stimulatory effect of hypotension on aortic chemoreceptor activity was measured in six of the seven cats in group (b) before and after propranolol injection. Isoproterenol infusion only moderately stimulated aortic chemoreceptor activity. This stimulation was blocked by propranolol. However, propranolol did not attenuate aortic chemoreceptor responses to hypoxia or to hypotension. We conclude that the beta-receptor adrenergic mechanism does not mediate oxygen chemoreception in the cat aortic body.     

Chemical respiratory control in chronically hyperoxic cats

Chemical control of respiration in cats after chronic normobaric hyperoxia (NH; inhalation of 100% O2 for 60-67 h) was compared with that of control rats, anesthetized with pentobarbital. After chronic hyperoxia, induction of moderate hypoxia (PaO2 = 50-60 Torr) increased inspiratory time (TI) often without increasing tidal volume (VT). More intense hypoxia (PaO2 = 40-50 Torr) depressed tidal volume and further increased TI, diminishing the respiratory drive (VT/TI). Hypercapnia, on the other hand, increased tidal volume and shortened respiratory cycle time; but these responses were subnormal. The normal stimulatory effects of intravenous nicotine and inhibitory effect of dopamine on carotid chemo-receptor activity and ventilation were preserved in the NH cats. Cyanide, however, did not stimulate carotid chemoreceptor activity and ventilation. Thus, the changes in the carotid and aortic chemosensory activities elicited appropriate reflex ventilation responses, indicating that the central component of the chemoreflex was not impaired. The ventilatory depression during hypoxia despite an active chemosensory input is consistent with the lack of carotid chemosensory response to and a central depressant effect of hypoxia in the NH cats, and was presumably associated in part with an increased responsiveness of airway reflexes. We conclude that chronic hyperoxia selectively attenuated carotid chemosensory and chemoreflex responses to hypoxia.     

Glutamate permeability at the blood-brain barrier in insulinopenic and insulin-resistant rats

The influence of diabetes on brain glutamate (GLU) uptake was studied in insulinopenic (streptozotocin [STZ]) and insulin-resistant (diet-induced obesity [DIO]) rat models of diabetes. In the STZ study, adult male Sprague-Dawley rats were treated with STZ (65 mg/kg intravenously) or vehicle and studied 3 weeks later. The STZ rats had elevated plasma levels of glucose, ketone bodies, and branched-chain amino acids; brain uptake of GLU was very low in both STZ and control rats, examined under conditions of normal and greatly elevated (by intravenous infusion) plasma GLU concentrations. In the DIO study, rats ingested a palatable, high-energy diet for 2 weeks and were then divided into weight tertiles: rats in the heaviest tertile were designated DIO; rats in the lightest tertile, diet-resistant (DR); and rats in the intermediate tertile, controls. The DIO and DR rats continued to consume the high-energy diet for 4 more weeks, whereas the control rats were switched to standard rat chow. All rats were studied at 6 weeks (subgroups were examined under conditions of normal or elevated plasma GLU concentrations). The DIO rats ate more food and were heavier than the DR or control rats and had higher plasma leptin levels and insulin-glucose ratios. In all diet groups, the blood-brain barrier showed very low GLU penetration and was unaffected by plasma GLU concentration. Brain GLU uptake also did not differ among the diet groups. Together, the results indicate that the blood-brain barrier remains intact to the penetration of GLU in 2 models of diabetes under the conditions examined.     

Patient communication during cataract surgery

PURPOSE: Most cataract surgery is now performed under local anaesthesia on a day-case basis. As patients are fully conscious during the procedure, it is important that they remain still. There are a variety of reasons why patients may need to move, and it is important that the surgeon is made aware that this may happen. Some centres offer a nurse's hand as a means of perioperative patient communication. We sought to study the safety and efficacy of using an electronic patient-controlled alert device. METHOD: We compared hand-holding with the use of a patient alert device, and with both communication methods at the same time, on 150 subjects undergoing cataract surgery under local anaesthesia. Assessment of pre- and postoperative state anxiety was undertaken and patients' satisfaction with the communication strategies was assessed. RESULTS: There was a significant difference between pre- and postoperative state anxiety for each group (P<0.001) but no significant differences in pre-, peri-, or postoperative state anxiety between groups. There were no significant differences in confidence, pain, understanding, satisfaction, memory, and reassurance between the three groups. A total of 46% of all patients reported experiencing one or more of the potential problems enquired about, during the operation. Significant correlations were also identified between some of the psychological variables investigated. CONCLUSIONS: An electronic patient alert device is as effective a means of perioperative patient communication as holding a nurse's hand, during cataract surgery under local anaesthesia. It is safe, reassuring and it allows patients to communicate directly with the surgeon.     

INTRAHEPATIC CHOLANGIOJEJUNOSTOMY FOR MALIGNANT HILAR BILIARY OBSTRUCTION: APPROACH TO THE LEFT HEPATIC DUCT

Biliary enteric anastomosis for relief of biliary obstruction caused by malignancy at the confluence of the bile ducts can be difficult due to non availability of an adequate length of duct for anastomosis. This paper describes an approach to the left hepatic duct to decompress the biliary tree and its successful application in 11 of 12 patients who presented with malignant hilar obstruction.KEYWORDS: Hepaticojejunostomy, Malignant biliary obstruction