Phosphorylase kinase deficiency

Phosphorylase kinase deficiency in I strain mice and in humans both show X-chromosomal inheritance. Neither deficient adult humans nor deficient mice show any sign of disease. Thus the two conditions resemble each other. However, there are differences. The enzyme is only partially deficient in human patients in liver, muscle, and blood cells; in mice the deficiency is complete and seems to be confined to the muscles.This paper was presented at a symposium entitled Genetic Control of Mammalian Metabolism held at The Jackson Laboratory, Bar Harbor, Maine, June 30–July 2, 1969. The symposium was supported in part by an allocation from NIH General Research Support Grant FR 05545 from the Division of Research Resources to The Jackson Laboratory.Supported by grant AM 13359 of the National Institutes of Health.     

Interaction of α-lactalbumin with dimyristoyl phosphatidylcholine vesicles. I. A microcalorimetric and fluorescence study

α-Lactalbumin and dimyristoyl phosphatidylcholine were used as a prototype to study the influence of a protein conformational change, induced by the pH, on the interaction between that protein and a phospholipid.The enthalpy changes associated with the interaction of α-lactalbumin with dimyristoyl phosphatidylcholine vesicles were measured as a function of the molar ratio of phospholipid to protein, pH and temperature. Gel-filtration, electron-microscopic and fluorescence data for the same experimental conditions were also obtained. At pH 4 and 5, the enthalphy changes (ΔH) are not only larger than at physiological pH, but also show a maximum at about 23°C in the ΔH vs. temperature graph. At pH 6 and 7, on the contrary, ΔH increases with decreasing temperature without a maximum in the curve. Gel-chromatographic and electron-microscopic data show that at pH 6 and 7, the morphological characteristics of the vesicles are unchanged upon addition of α-lactalbumin, while at pH 4 and 5 at 23°C an extra peak appears in the gel-filtration graphs between the pure vesicles and α-lactalbumin. The new fraction contains lipid-protein complexes. Electron micrographs show that bar-shaped entities are formed. A red shift at 23°C and a blue shift at 37°C, both to 336 nm, are observed for λ_max of the fluorescence emission spectra at pH 4 when α-lactalbumin is brought into contact with the phospholipid. At the same time, a strong increase in the fluorescence intensity is observed. The chromatographic and fluorescence data indicate that a lipid-protein complex with a molar ratio of approx. 80 is formed. At pH 7 and different temperatures, the emission maximum remains at the wavelength of pure α-lactalbumin, the change in the fluorescence intensity, however, indicates that interaction with the lipid occurs.The results can be explained on the basis of an electrostatic interaction at pH 6 and 7, and a hydrophobic interaction at pH 4 and 5.     

Behavioral profile of ψ-MSH: Relationship with acta and β-endorphin action

In view of the close structural similarity of the pro-opiocortin fragment γ-MSH and of ACTH/MSH type peptides, the behavioral profile of γ-MSH was explored. Attention was first focussed on behavioral procedures in which ACTH/MSH related neuropeptides have been found effective. Using different procedures to test avoidance behavior, it was found that γ-MSH and ACTH-like neuropeptides had opposite effects. In this respect the activity of γ-MSH resembles that of opiate antagonists rather than that of β-endorphin. Accordingly, ACTH_1–24-induced excessive grooming which is blocked by opiate antagonists, is attenuated by γ-MSH. In addition, γ-MSH injected into the periaqueductal gray matter of the brainstem of opiate naive rats elicited symptoms reminiscent of those seen after opiate withdrawal. γ-MSH attenuated more or less several effects of intracerebroventricularly administered β-endorphin (e.g. antinociception, hypothermia, α-MSH release) and decreased acquisition of heroin self-administration. Although γ-MSH at rather high doses displaced naloxone from its specific binding sites in brain homogenates, it did not interfere with β-endorphin-induced effects on in vitro muscle preparations (guinea pig ileum, rat rectum). Interestingly, γ-MSH induced relaxation of the rat rectum in vitro. It is postulated that γ-MSH may attenuate β-endorphin-induced effects by acting via γ-MSH receptor sites (functional antagonism), although a pharmacological antagonism cannot be excluded as yet.     

Low density lipoprotein receptor founder mutations in Afrikaner familial hypercholesterolaemic patients: a comparison of two geographical areas

Summary Afrikaners with familial hypercholesterolaemia (FH) were screened for the presence of three point mutations in the low density lipoprotein receptor gene that were previously described as being relatively common in this population. The prevalence and distribution of the mutations were compared in 27 unrelated homozygous and 79 unrelated heterozygous FH Afrikaner patients from two regions in South Africa, the Transvaal and Cape Provinces. The relative distribution of the three mutations was similar in the two regions, with the FH1 mutation being the most prevalent (66%), followed by the FH2 mutation (27%) and the FH3 mutation (7%). Interestingly, defects other than the three common mutations are more common in the Cape than in the Transvaal; thus the three known mutations account for 98% of FH alleles in the Transvaal and only 74% in the Cape Province. None of the patients carried the recently described familial defective apolipoprotein B100 mutation. These results establish that three founder mutant genes occur amongst the Afrikaner and are responsible for the overall high prevalence of FH in this population.     

Choroideremia: linkage analysis with physically mapped close DNA-markers

Summary We report linkage studies in 18 choroideremia (TCD) families using four closely linked polymorphic markers. Probe pZ11, which is known to be deleted in several unrelated patients with TCD, showed no recombinations (z _max 15.63 at = 0.00). In contrast, one recombination was observed with DXS367, which is also physically very close to TCD. Loci DXS95 and DXYS69 each showed more than one recombination with TCD. Moreover, these analyses revealed a double crossover between TCD and DXYS1, changing the previously reported very close linkage to a recombination fraction of 0.04 with a lod score of 9.93. Multipoint linkage analysis placed TCD proximal to DXS95-DXYS69 and very close to DXS367-pZ11 with almost identical multipoint lod score maxima either proximal to DXS367 (z _max= 23.43) or proximal to pZ11 (z _max=23.36). These results provide a refined linkage map around TCD and will also be useful in DNA diagnostics of the disease.     

Quantitative histochemistry of creatine kinase in rat myocardium and skeletal muscle

Summary Creatine kinase (ec 2.7.3.2) activity was demonstrated in rat myocardium using a polyvinyl alcohol-containing incubation medium and auxiliary enzymes. The activity was quantified by microdensitometry using both endpoint measurements and kinetic measurements. Control reactions were performed in the absence of creatine phosphate and ADP.The linear regression lines of the absorbances of reduced Nitro BT at the isobestic wavelength (585 nm) on incubation time were highly significant for both endpoint and kinetic measurements. The activity obtained from endpoint measurements was about 40% lower. This was caused by loss of the formazan reaction product from the tissue sections when the incubation medium was removed at the end of the reaction. The relationship between creatine kinase activity (test minus control reaction) and section thickness was not linear for either myocardium or skeletal muscle; control reactions, however, showed linear relationships with section thickness for both tissues. Limited penetration of auxiliary enzymes into the sections may be responsible for this disporportionality. Therefore, care should be taken in the interpretation of quantitative data obtained with different tissues.In conclusion, multi-step enzyme reactions can be used for quantitative histochemical purposes provided it is taken into account that the reactivity is not proportional to section thickness.     

Gustatory intensity discrimination in rat NTS: a tool for the evaluation of neural coding theories

Summary The neural coding of taste quality in vertebrates currently is addressed by the labeledline and the across-fiber pattern theory. Experimental tests that have tried to distinguish between these theories by manipulating taste quality have been problematic in that both are fairly successful. However, the two theories maintain that different numbers of neurons participate in coding the presence of a substance. In the labeled-line theory, only those neurons labeled by that substance are supposed to be involved, whereas in the across-fiber pattern theory, all neurons responding to the substance are taken into account. We therefore expected that the theories might predict different intensity discriminating abilities among the four classical taste stimuli, which could provide a less equivocal test between the theories.A previous paper (Maes 1984) described a model for the neural basis of intensity discrimination, based on signal-detection theory. In the present paper, experimental data obtained from single neurons in the nucleus of the solitary tract of rat are analyzed in terms of this model. Whole-mouth stimulation with the four classical taste substances was used. For both theories, predictions of the intensity discriminating acuity for the four substances were derived, using different response analysis intervals, and including two plausible non-linearities in neural processing.The acuity profile across the four stimuli (consisting of the reciprocals of the four differential thresholds) turned out to be sensitive to the choice of coding theory and non-linearity. The interval chosen for response analysis had a strong effect. The predicted profiles should be checked against behavioral data on intensity discrimination in rat, but since such data are not yet available, a comparison was made with human psychophysical data, for illustrative purposes. It appeared that a unique combination of variables (tonic part of the response, across-fiber pattern coding with a contrast enhancement type of non-linearity) could be selected to match the psychophysical profile.In the Discussion, special attention is paid to the fundamental differences between the two coding theories, to the relevance of whole-mouth stimulation, and to the informational significance of various parts of the phasic/tonic response.Abbreviations AFP across-fiber pattern - CT chorda tympani - DA discrimination acuity - DT differential threshold - H sour - LL labeled line - N salty - NTS nucleus tractus solitarius - PTA pontine taste area - Q bitter - S sweet