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Biomedical subjects

W Krone

Publications and source records attributed to W Krone.

At least 181 records · Page 10Linked to original sources
PubMed1978

Analysis of banding patterns and mosaic configurations in a case of ring chromosome 15.

Cytogenetic studies on lymphocytes from a 14-year-old mentally retarded girl with somatic anomalies suggestive of a chromosomal abnormality revealed a ring chromosome 15. The long arm of the defective chromosome is broken at band q24 or q25. The silver staining technique for nucleolus organizer regions showed that the ring had lost the achromatic stalk and the satellite. The chromosomal mosaicism resulting from the structural instability of the ring chromosome was analyzed and compared with 6 cases reported in the literature. It is proposed that the clinical manifestations in the different patients with ring chromosome 15 result from both the deficiency in the long arm and the mosaic configurations.

Adolescent↗
PubMed1977

Gene dosage effect for fumarate hydratase (FH; E.C. 4.2.1.2) in partial trisomy 1.

A strain of fibroblasts partially trisomic for the larger part of 1q (Norwood and Hoehn, 1974) contains about 1.5 times as much fumarate hydratase (FH) as various control-strains. This gene dosage effect was ascertained by (1) comparative measurements of the specific activity; (2) relating the specific activity of FH to that of reference enzymes, not influenced by the chromosomal anomaly; and (3) by immunoprecipitation methods, using a rabbit antiserum against pig heart FH which cross-reacts with the human enzyme. Among others, this gene dosage effect can be demonstrated numerically by the following parameters: Ratio of the average specific activity of FH in the trisomic strain to that of the control strains: 1.53. Corresponding ratio after dividing FH activity by that of reference enzymes; for acid phosphatase: 1.58, for glutamate dehydrogenase: 1.53. Average ratio of the immunoprecipitation areas obtained upon radial immunodiffusion according to Mancini et al. (1965): 1.56.

Acid Phosphatase↗
PubMed1977

Frequency of Ag-stained nucleolus organizer regions in the acrocentric chromosomes of man.

The Ag-stainability of the nucleolus organizer region (NOR) was studied in the acrocentric chromosomes identified by Q-banding of cultured lymphocytes in 51 karyotypically normal persons (31 males and 20 females). A consistent pattern of Ag-positive NORs was found in each individual. Ninety percent of individuals have a model number of 8--10 Ag-positive NORs per cell. The frequency of Ag-positive NORs is similar in all five acrocentrics. A statistically nonsignificant lower frequency is found in chromosome 22. Ag-negative NORs on both homologues were found in four cases. The observed frequency distribution of individuals with homozygous NOR-positive, heterozygous, and homozygous negative acrocentric chromosomes was in accordance with the Hardy-Weinberg law in all five pairs of the acrocentric chromosomes as well as in total. No sex difference was observed on our material.

Cell Nucleolus↗
PubMed1977

Physiological regulation of rat liver phosphoenolpyruvate carboxykinase (GTP) by insulin. Insignificance of a cyclic AMP-independent mechanism.

The effect of re-feeding glucose, protein or fat and the effect of insulin injection on the activity of hepatic phosphoenolpyruvate carboxykinase (GTP: oxaloacetate carboxy-lyase (transphosphorylating) EC 4.1.1.32), the concentration of hepatic cyclic AMP and the level of serum insulin was investigated in starved rats. Under all conditions examined the concentration of serum insulin was elevated to a high degree. However, only rats re-fed with glucose responded to the increase in serum insulin with a decrease in PEP carboxykinase activity, while the activity of the enzyme remained unchanged or was elevated after re-feeding protein or fat or after insulin injection, respectively. Since under all conditions there was a close correlation between cyclic AMP concentration and PEP carboxykinase activity, but not between the insulin level and enzyme activity, it is concluded that the hormone physiologically regulates PEP carboxykinase activity by decreasing the intrahepatic cyclic AMP concentration rather than by the postulated cyclic AMP-independent inhibition of specific mRNA translation.

Animals↗
PubMed1976

Interaction between glucocorticoids and cyclic AMP in the regulation of phosphoenolpyruvate carboxykinase (GTP) in the isolated perfused rat liver. Effects of cordycepin and cycloheximide.

The mechanism of the interaction between glucocorticoids and cyclic AMP in the regulation of phosphoenolpyruvate carboxykinase (GTP: oxalocetate carboxylase, transphosphorylating, EC 4.1.1.32) was investigated in the isolated perfused rat liver using inhibitors of transcription or translation. Dibutyryl cyclic AMP produced a rapid increase in P-enolpyruvate carboxykinase activity. The response of the enzyme to the cyclic nucleotide ceased however, at 4 h, but was restored by dexamethasone. The dibutyryl cyclic AMP-induced increase in P-enolpyruvate carboxykinase activity was completely blocked by cycloheximide, but not not by cordycepin. However, cordycepin totalaly suppressed the "permissive" effect of dexamethasone on the response of the enzyme to dibutyryl cyclic AMP. Preperfusion of the livers with dexamethasone and cycloheximide, following by perfusion without the steroid hormone and the inhibitor, resulted in a rapid rise in P-enolpyruvate carbosykinase activity, which was not affect by cordycepin. If livers were preperfused with cordycepin for different time-periods, followed by dibutyryl cyclic AMP stimulation of P-enolpyruvate carboxykinase synthesis, the response of the enzyme to the cyclic nucleotide was progressively reduced, achieving 50% inhibition after 1.5 h of preperfusion. These results suggest that the induction of hepatic P-enolpyruvate carboxykinase to maximum values, brought about by cyclic AMP at the level of translation, depends on the supply of newly synthetized mRNA provided by the transcriptional action of glucocorticoids.

Animals↗
PubMed1976

Effect of cold exposure on phosphoenolpyruvate carboxykinase (GTP) activity and cyclic amp concentration in livers of starved rats. Role of glucorticoids.

The effect of cold exposure (5 degrees C) on the concentration of cyclic AMP and on the activity of phosphoenolpyruvate carboxykinase (GTP: oxaloacetate carboxy-lyase (transphosphorylating), EC 4.1.1.32) was investigated in the liver of intact and adrenalectomized starved rats. Intact starved rats responded to cold exposure with a large increase in both the concentration of hepatic cyclic AMP and the activity of phosphoenolpyruvate carboxykinase above the starvation level. Adrenalectomy did not impair the cold-induced maximum elevation of cyclic AMP but totally prevented the response of the enzyme to cold. Yet, this response was completely restored by hydrocortisone treatment, while the steroid per se had no effect on enzyme activity. In isolated perfused livers of intact starved rats dibutyryl cyclic AMP provoked an immediate dramatic increase in phosphoenolpyruvate carboxykinase activity above the starvation level even if mRNA synthesis was inhibited by cordycepin. However, cyclic AMP was ineffective in increasing enzyme activity in livers of adrenalectomized rats. From these results it is suggested (i) that in starved rats the adaptation to the enhanced glucose demand provoked by cold exposure includes the induction of hepatic phosphoenolpyruvate carboxykinase above the starvation level, (ii) that this induction is due to the cold-induced increase in hepatic cyclic AMP levels, (iii) that cyclic AMP stimulates enzyme synthesis at a post-transcriptional step and (iv) that the cold-induced cyclic AMP-mediated induction of phosphoenolpyruvate carboxykinase above the starvation level requires the "permissive" effect of glucocorticoids.

Adrenalectomy↗
PubMed1976

The relationship of a specific chromosomal region to the development of the acrosome.

In early spermatids of Urodeles the chromosome segments bearing constitutive heterochromatin are localized in one half of the round nucleus; this region becomes the basal part of the long nucleus of the spermatozoon. The euchromatic chromosome segments extend toward the anterior nuclear pole in a bouquet configuration (Macgregor and Walker, 1973). In the course of spermiohistogenesis, one of the heterochromatic regions (the acrosomal chromocenter) migrates from the basal part to the anterior half of the spermatid nucleus. This heterochromatic block is identical with a species-specific, definite C-band in the karyotype. This relationship between the acrosomal chromocenter and a specific chromosomal C-band was established in Triturus cristatus, T. marmoratus, T. alpestric and Cynops pyrrhogaster. In closely related species this particular C-band lies on similar chromosomes. - While the spermatid nucleus still retains its round shape the acrosomal chromocenter despiralizes into a long heterochromatic thread (acrosomal thread). Precisely at the position of this thread the nucleus evaginates and acquires a pear-like shape. During the elongation of the nuclear protrusion the acrosomal thread remains associated with the anterior end. At termination of spermiogenesis it lies closely below the acrosome in the tip of the spermatozoon. Spontaneous aberrations which affect the acrosomal chromocenter or the thread lead to the development of spermatozoa with defective tips. - Several euchromatic segments, interspersed between the heterchromatic segments, can be recognized in the completely despiralized acrosomal thread. Genes responsible for the morphogenetic activities of both, the acrosomal chromocenter and the acrosomal thread, in the development of the spermtip, might be localized in these interspersed euchromatic segments. The existence in higher vertebrates of an acrosomal chromocenter or an equivalent chromosomal region is discussed.

Acrosome↗
PubMed1976

Induction of rat liver phosphoenolpyruvate carbonxykinase (GTP) by cyclic AMP during starvation. The permissive action of glucocorticoids.

The effect of starvation on the activity of hepatic phosphoenolpyruvate carboxykinase (GTP:oxaloacetate carboxy-lyase (transphosphorylating), EC 4.1.1.32), and on the response of the enzyme to N6-O2'dibutyryl adenosine 3', 5'-monophosphate was investigated in intact and glucocorticoid-deprived rats. In the liver of intact animals, starvation produced a rapid increase in the concentration of cyclic AMP and a corresponding increase in the activity of phosphoenolpyruvate carboxykinase. The kinetics of both changes were not affected by adrenalectomy. Injection of N6-O2'-dibutyryl adenosine 3', 5'-monophosphate into intact starved rats resulted in an immediate, dramatic increase in phosphoenolpyruvate carboxykinase activity above the starvation level. Adrenalectomy completely blocked the response of the enzyme to the cyclic nucleotide. Restoration of hydrocortisone to the adrenalectomized animals restored the full N6-I2'dibutyryl adenosine 3', 5'-monophosphate effect after a lag period of 2 h. The physiological significance of these findings is considered. The data are interpreted with regard to the current hypothesis that glucocorticoids promote an increase in translatable phosphoenolpyruvate carboxykinase mRNA, while cyclic AMP enhances the translation of preexisting specific mRNA templates.

Adrenalectomy↗
PubMed1976

Physiologic significance of glucocorticoids and insulin in the regulation of hepatic gluconeogenesis during starvation in rats.

The physiologic significance of glucocorticoids and insulin in the regulation of hepatic gluconeogenesis was investigated during a 48-hr starvation period by studying the factors presumed to control the rate of glucose synthesis in the final gluconeogenetic pathway. Rats were used, in which glucorticoids were removed by adrenalectomy before starvation, and in which serum insulin was kept constant before and after food withdrawal by pre-feeding with a proteinfree diet. It was found that adrenalectomized rats at constantly low serum insulin levels responded to starvation as rapidly, and to the same degree, as intact control subjects (1) by a significant increase in plasma glucagon and, consequently, in hepatic cAMP concentration; (2) by a coordinate elevation of the activities of hepatic pyruvate carboxylase, P-enolpyruvate carboxykinase, and fructose-1,6-diphosphatase; (3) by systematic alterations in the concentration of effectors of gluconeogenetic key enzymes; (4) by a shifting of the cytoplasmic NAD system towards the reduced state; (5) by a decrease in the intrahepatic concentration of glycogenic precursor substrates. These results suggest that the hepatic gluconeogenic response to starvation with respect to the regulatory factors 1-5 occurs independently from changes in the concentration of plasma glucocorticoids and insulin. The crossing over of the gluconeogenetic intermediates between pyruvate and P-enolpyruvate (PEP), which was observed in intact but not in adrenalectomized rats, supports the assumption that during starvation, glucocorticoids enhance the rate of glucose production by the liver predominantly by permitting hepatic cAMP to stimulate the yet undefined mechanism, which has been demonstrated in the isolated perfused rat liver to control the substrate flow between pyruvate and PEP.

Adenine Nucleotides↗
PubMed1976

Concentration of cyclic AMP in rat liver as a function of the insulin/glucagon ratio in blood under standardized physiological conditions.

The concentration of insulin and glucagon in peripheral blood and the concentration of cAMP in liver was followed in rats throughout a 48 hour starvation period and up to 6 hours afer refeeding glucose or casein. By so changing the insulin/glucagon molar ratio from minimum to maximum values, simultaneous inverse changes in the concentration of hepatic cAMP could be induced. The study, thus, suggests that during a starvation-refeeding cycle the level of cAMP in the liver is regulated predominantly by the insulin/glucagon ratio in the blood. Possible criticisms of this conclusion are discussed.

Adrenalectomy↗
PubMed1975

Biochemical and cytogenetic studies on the nucleolus organizing regions (NOR) of man. II. A family with the 15/21 translocation.

The amount of ribosomal DNA (rDNA) was determined quantitatively by RNA-DNA hybridization in the genomes of a mother and her daughter, both with the karyotype 45,XX,t(15q21q). The saturation values found were 0.030% (mother), 0.023% (daughter), and 0.022% for the husband and father of the daughter. A detailed cytogenetic analysis of the short arms of the acrocentric chromosomes of these probands allowed the biochemical results to be interpreted in terms of the size of the individual set of nucleolus organizing regions (NORs) present in each proband. The correlation existing between the biochemical and the cytogenetic findings shows that the amount of rDNA in the human genome is not primarily a function of the number of acrocentric chromosomes, but depends on the individual combination of variant NORs occurring in the human genome.

Cell Nucleolus↗