Spectral opponency of on-type ganglion cells and the blue preference of Rana pipiens

Spectrally opponent processes of ON-type retinal ganglion cells and the blue preference behavior were identified by parallel physiological and behavioral experiments in Rana pipiens. Spectral opponency of retinal ON-units was measured by recording from optic nerve terminals in the anterior thalamus, while the retina was stimulated by combinations of monochromatic stimuli. Spectral opponency of the blue preference was determined in a Y-maze, using similar combinations of monochromatic stimuli. The opponent processes of the ON-units and blue preference are similar in the spectral ranges of excitatory and inhibitory effects. In both cases the spectral opponency can be described as short wavelength excitation and long wavelength inhibition. The data suggest that the short wavelength excitation is based, at least in part, on the green rod (P432) channel, while the long wavelength inhibition is caused, at least in part, by stimulation of the principal and/or single cone (P580) channel. A model is presented to show how receptor interactions may encode this spectrally opponent process. The results support the hypothesis that the blue preference is dependent on information supplied to the anterior thalamus by ON-type retinal ganglion cells.     

The effect of PCO2 on hypoxic pulmonary vasoconstriction

Lung areas with a low V/Q ratio cause hypoxaemia. The low alveolar oxygen concentration may cause local hypoxic pulmonary vasoconstriction (HPV) which reduces perfusion, raises the V/Q ratio, and hence reduces the tendency to a low PaO2. By changing PCO2, the HPV response can be altered. We examined this relationship in anaesthetized dogs by using a tracheal divider to separate hypoxic (nitrogen ventilated) from oxygenated (100 per cent oxygen ventilated) lung. Relative perfusion was assessed from total 133Xe exhaled from each lung area after intravenous infusions. When PaCO2 was changed by changing ventilation, we found that an increasing PaCO2 increased HPV and also PaO2. At a PaCO2 of 3.3 kPa, HPV was abolished and PaO2 fell. We also changed PaCO2 by altering PICO2 to one or both lung areas while ventilation remained constant throughout the experiment. Again as PaCO2 increased, HPV and PaCO2 increased. When PaCO2 fell and end tidal carbon dioxide in the hypoxic lung (PETCO2) remained elevated by maintaining PICO2 in the hypoxic lung and removing CO2 from the oxygenated lung) HPV was maintained. Thus it is the alveolar concentration of CO2 in the hypoxic lung which is important in modifying HPV. We conclude that in this model a low PETCO2 (3.3 kPa) in hypoxic lung will reduce HPV, and will result in more severe hypoxaemia. This may have relevance in both anaesthetized and intensive care unit patients when a higher PaO2 may be obtained by increasing hypoxic lung PETCO2. The effect of PETCO2 on PaO2 will be influenced by other variables, but when hypoventilated or hypoxic exist, increasing PETCO2 may reinforce hypoxic pulmonary vasoconstriction and thus may increase PaO2.     

Management of postoperative pelvic lymphoceles

Lymphoceles following pelvic surgery are not rare events. The management of this postoperative complication in 18 patients included needle aspiration, external drainage, and intraperitoneal marsupialization. The following diagnostic and therapeutic approach is recommended: ultrasonographic definition of the lymphocele; excretory urography to assess upper urinary tract obstruction; observation of small, nonobstructing, asymptomatic lymphoceles; needle aspiration for diagnosis confirmation; intraperitoneal marsupialization for noninfected, large lymphoceles that are obstructing the upper urinary tract or are symptomatic; and incision and drainage of small or infected lymphoceles.     

Further characterisation of allergens associated with hypersensitivity to the "green nimitti" midge (Cladotanytarsus lewisi, Diptera: Chironomidae)

Chironomid midges are small (2-15 mm) non-biting flies, characteristically seen swarming by water at dusk. Allergens of the "green nimitti" midge, Cladotanytarsus lewisi (Freeman) (Diptera: Chironomidae), a cause of widespread hypersensitivity in the Sudan, were isolated and partially characterized by Sephacryl S200 chromatography. The allergenicity of the fractions was identified by "rocket" autoradiography, RAST inhibition, skin "prick" tests, and the immunoblot technique. The fractions were further analysed by isoelectric focusing and SDS-PAGE. Two major allergens with pI's ranging from 4.3 to 6.0 were identified and had molecular weights of approximately 17,000 and 32,000 daltons, sizes compatible with their being monomeric and dimeric haemoglobins. Since chironomids occur in nuisance numbers worldwide and their haemoglobins have been shown to produce severe hypersensitivity reactions in man, they should be seen as an important potential cause of environmental and occupational allergy.     

Cold Agglutinin Formation in Patients Undergoing Haemodialysis. A Possible Relationship to Dialyser Re-use

Summary: Cold agglutinin formation in patients undergoing haemodialysis. A possible relationship to dialyser re-use.
Cold agglutinins with anti-N characteristics were shown to develop in as short a time as four months in patients on home dialysis. It appeared that the development of such antibodies is related to dialyser re-use. Those who were treated without re-using their dialyser did not develop these antibodies.
Anti-N may cause early graft failure associated with agglutination in a cold allograft. Moreover, if these antibodies develop in patients on dialysis there may be problems with extracorporeal dialysis and blood transfusion.     

Chromosome Banding Studies in Acute Leukaemia at Diagnosis

Cytogenetic study by a chromosome banding technique has been attempted in 93 cases of acute leukaemia at diagnosis. Banding patterns were difficult to visualise in the bone-marrow chromosomes of patients with acute leukaemia because of the fuzzy appearance of the fixed metaphases. The proportion of patients with abnormal chromosomes was higher in acute lymphoblastic (ALL) than in acute myeloid (AML) leukaemia. Abnormalities were present in all cases of other cytological types. Hyperdiploidy was the most commonly found numerical error in both ALL and AML but a larger proportion of patients with ALL had hyperdiploidy in more than 30% of the cells. In ALL it was generally found that the higher the frequency of hyperdiploidy the greater was the number of chromosomes per cell. Hypodiploidy not attributable to random losses was found in only 6 patients. Clones identified by rearranged or marker chromosomes were found in all types of leukaemia. Clones marked by a 7q-chromosome, in which the break point was the same, were identified in 1 adult with ALL and 2 children with AML. The high frequency of randomly distributed chromosomal breakage found in the bone-marrow chromosomes of a high proportion of the patients may be related to the disease process.