Absorption of radioactive lead (210Pb) by different parts of the intestine in young and adult rats.

Absorption of radioactive lead (210Pb) was studied in an intestinal preparation from adult and young rats. Absorption was higher in the jejunal parts than in the duodenum or colon. Moreover, absorption in young rats was greater than in adults. No difference in absorption was found after loading with large amounts of lead. Maintaining the animals on a low calcium diet decreased rather than increased lead absorption.     

Respiratory and cardiac responses to exercise-simulating peripheral perfusion in endurance trained and untrained rats. II. Temporal relationships between outflow parameters and cardiac and respiratory responses

In endurance trained (TR) and untrained (UTR) rats heart rate (HR) and respiratory rate (RR) were recorded during perfusion of the circulatorily isolated hind leg of the rat with exercise simulating modified tyrode solutions (TR:n = 10, UTR:n = 10; compare part I). During the 20 min test period and the preceding and succeeding periods of control perfusions with an unmodified tyrode solution, [lactate], pH, [K+], [Na+], PO2 and PCO2 were measured in the outflow of the femoral vein. In 3 experimental series: (1) hypoxic tyrode solution enriched with lactic acid (15 mmol.l-1), (2) normoxic solution with lactic acid, (3) hypoxic solution without lactic acid, were applied. The outflow parameters were cross correlated with both HR and RR. The analysis revealed a significant temporal relationship between [lactate], pH, PO2, PCO2 and [K+] and both HR and RR. In the trained rats no temporal correlation between either of the outflow and reflex parameters could be determined. This result was not due to low [lactate], but was also found during perfusion with lactic acid. In all 3 test conditions [lactate] in untrained individuals was best correlated with both HR and RR. Although the correlation peaks of the respiratory response, but not of the HR response were definitely lower in normoxic lactic and perfusion than in the two other experimental conditions, both inter- and intraindividual correlation analyses revealed a high degree of interdependence between respiratory and cardiac responses.     

Head-to-head dimerization of parallel beta helices in a synthetic model of the linear gramicidins

In chloroform solution, the D ,L -alternating stereo-co-oligopeptide HCO-L -Phe-(D -Phe-L -Phe)₃-OMe (I) forms three major species, two of which are dimeric and one tetrameric. One of the two dimeric species gives a specific set of ¹H-nmr signals at 25°C; the other, together with the tetrameric species, gives another set of resonance signals. In a carbon tetrachloride or cyclohexane solution at 25°C, I forms virtually only the tetrameric species. From the nmr data, it can be shown that the dimeric and tetrameric species, that are in rapid equilibrium with each other in chloroform solutions, are a right-handed ↑↑β^5.6 helical dimer and the head-to-head (formyl-ends-to-formyl-ends) dimerization product of this dimer. It is suggested that the linear gramicidins may also form head-to-head dimers of parallel β helices, as observed for the model oligopeptide I.     

Evidence of genetic heterogeneity of Leber's congenital amaurosis (LCA) and mapping of LCA1 to chromosome 17p13

Leber’s congenital amaurosis (LCA) is an autosomal recessive disease responsible for congenital blindness. It is the earliest and most severe inherited retinal dystrophy in human and its genetic heterogeneity has long been recognised. We have recently reported on the first localisation of a disease gene (LCA1) to the short arm of chromosome 17 by homozygosity mapping in five families of North African origin. Here, we refine the genetic mapping of LCA1 to chromosome 17p13 between loci D17S938 and D17S1353 and provide strong support for the genetic heterogeneity of this condition (maximum likelihood for heterogeneity, 17.20 in lnL; heterogeneity versus homogeneity, P = 0.0002, heterogeneity versus no linkage, P < 0.0001) Received: 23 October 1995 / Revised: 11 January 1996     

Fibroblast dedifferentiation as a determinant of successful regeneration

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