摘要:

ExtractPhenylalanine hydroxylase activity is present in the liver of human fetuses after the 8th week of gestation, and activities similar to those found in liver from adult control subjects are reached at around the 13th fetal week. The mean enzyme activity in fetal liver after the 13th week of gestation was 107 μmoles tyrosine formed per g protein per hr, and 130 μumoles in livers from adult control subjects. In premature infants soon after birth the mean enzyme activity was 67 μmoles tyrosine formed. This difference from the level of activity in fetuses could be due to loss of activity during the 1–3-hr delay in obtaining liver samples after death. When the pteridine cofactor was omitted from the enzyme assay system only very low activity was found in the livers of fetuses which were studied. Tyrosine was formed when isolated fetal livers were perfused with phenylalanine. The Kmfor phenylalanine hydroxylase from the liver of human fetuses was 9 × 10-4m and for liver from adults was 1 × 10-3m. Thus, the human fetus and immature newborn infant do not lack phenylalanine hydroxylase in the liver.SpeculationThe human fetus and immature newborn infant have considerable phenylalanine hydroxylase activity in the liver. The hyperphenylalaninemia or reduced tolerance for phenylalanine found in some infants with low birth weight should thus, not be paralleled with a transient form of phenylketonuria, but could rather be caused by a reduced efficiency of some other component of the phenylalanine-hydroxylating system.

ISSN:0031-3998    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

ExtractQuantitation of human genes for ribosomal RNA (rRNA) was possible by molecular DNA/RNA hybridization on nitrocellulose discs. Labeled ribosomal RNA hybridizes with an average of 14 × 10-5of the total human DNA. If we assume that the diploid cell contains 5.5 × 1012daltons of DNA, the ribosomal RNA hybridizes with 7.7 × 108daltons of ribosomal DNA (rDNA), which is equal to about 320 genes. Hybridization of rRNA with DNA of three different diploid sources shows a rRNA/DNA ratio which varies from 12–15.4 × 10-5. The rRNA/DNA ratio of DNA derived from trisomy 21 cells is not significantly different from the normal cells. The genes for rRNA were found to resist melting at temperatures 10° or more above the Tm. This property permits enrichment of these genes by thermal fractionation.SpeculationRibosomal RNA genes are probably present on several human chromosomes. The ability to enrich these genes in relation to the whole human DNA indicates that they are clustered.

ISSN:0031-3998    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

ExtractHistochemical and ultrastructural consequences of pH variations in growth media were studied using three normal human fibroblast strains. Histochemical staining for acid phosphatase indicated increased amounts of enzyme activity in cells grown at higher pH. The ultrastructural consequences of an increase in growth medium pH was dramatic. A picture resembling storage disease developed in these cells within a few days. The cells became filled with bodies which could roughly be divided into two types. Type I had a homogeneous matrix, stained slightly with ruthenium red, was usually not membrane bound, and exhibited no acid glycerophosphatase activity. The nature and origin of these bodies is unclear. Type II bodies contained whorles of membranes and inhomogeneous matrix which was acid phosphatase positive but did not stain with ruthenium red. This type was always membrane bound and qualifies as lysosomes. Normal cells thus grown at higher pH were morphologically similar to cells cultured at neutral pH from patients with I-cell disease. These morphologic changes did not affect cell viability or cell growth.SpeculationA morphologic picture of severe storage disease can be induced in normal fibroblasts simply by increasing the medium pH. This is in agreement with our earlier observation that the lysosomal function of mucopolysaccharide degradation is progressively inhibited as pH of the growth medium increases. When attempting to diagnose genetic disease in cultured cells it is important to realize that intracellular lysosomal function is sensitive to extracellular pH. The observation of such pH sensitivity might also be a useful tool in studies on the general nature of lysosomal function.

ISSN:0031-3998    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

ExtractFocal electrical stimulation of the medulla was undertaken in exteriorized fetal sheep and neonatal lambs, anesthetized with pentobarbital. The area from which respiratory responses were obtained was mapped using stereotaxic coordinates. Focal stimulation of the fetal medulla caused one or two inspiratory gasps. In only a few instances was the response expiratory and this appeared to be nonspecific. The area in the fetal brain stem from which respiratory responses were elicited was diffuse and extended from obex to lower pons. This region occupied a volume of about 130 mm3.In one exteriorized fetus with spontaneous, rhythmic ventilation, focal stimulation caused an apneic pause. Later when respiration ceased spontaneously, focal stimulation at the same current strength induced inspiratory gasps. In the spontaneously breathing neonatal lamb, focal stimulation of the medulla was associated with a diminution in tidal volume and an apneic pause could be produced with an increase in current strength. The apneic pause occurred at about the same current strength as that required to initiate respiration in the fetus.In the neonatal lamb the brain stem area from which a respiratory response could be obtained was less diffuse than that of the fetus and occupied a volume of about 65 mm3. This region was similar to the inspiratory center of adult sheep reported by others.SpeculationThe respiratory center of the fetus appears to be just as sensitive to focal electrical stimulation as that of the neonatal animal. However, differing ventilatory response to stimulation depending on the presence or absence of respiration suggests a different functional organization of the fetal respiratory center. This is further supported by the characteristic inspiratory response of the fetus and the diffuse area from which such a response was obtained.

ISSN:0031-3998    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

AbstractThrough the use of a double antibody radioimmunoassay method, the mean serum concentration of thyrotropin (TSH) in 51 normal children aged 1 month-18 years was 3.7 ng/ml. There was no change with age, sex, or time of the day at which the sample was obtained.In six of nine newly diagnosed hyperthyroid children concentrations of TSH fell below the limit of detection, whereas in the remaining three concentrations were in the low normal range. Knowledge of the TSH fluctuations during medical treatment (antithyroid drugs or radioactive iodine plus127I) were useful in insuring a smooth clinical course. Elevations in TSH above 10 ng/ml served to indicate a need for change in therapy. Radical subtotal thyroidectomy evoked an acute compensatory rise (> 20 ng/ml) in TSH levels which was sometimes sufficient to maintain the level of serum thyroxine above 4 μg/100 ml. Hemithyroidectomy did not influence TSH or other thyroid parameters in previously euthyroid subjects.There was a clear separation between normal subjects and patients with primary hypothyroidism with values for TSH always exceeding 20 ng/ml in the latter. The TSH levels were below 3.7 ng/ml in pituitary hypothyroidism. In hypothyroid patients receiving adequate replacement therapy, elevations of serum TSH of > 20 ng/ml were encountered 2 weeks after discontinuation of treatment.Investigation of the pituitary-thyroidal axis in two untreated cretinous infants showed preservation of the functional integrity of the pituitary-thyroidal feedback system despite prenatal thyroid insufficiency as evidenced by a fall of TSH from levels >80 to <5 ng/ml in the presence of free thyroxine (FT4) levels >2 ng/100 ml.In three patients (two females and one male) with longstanding juvenile hypothyroidism and TSH levels >80 ng/ml, pituitary dysfunctions characterized by luteinizing hormone (LH) concentrations above 20 mIU/ml and blunted growth hormone (HGH) responses to hypoglycemia were documented prior to therapy. Only the male had evidence of sexual precocity on physical examination. All three showed an abnormal circadian rhythm of cortisol secretion manifested by 8 PM values greater than 10 7mu;g/100 ml. Acute restoration of euthyroidism in the two girls by means of paren-teral thyroxine (T4) improved the HGH response and normalized the cortisol rhythms in 72 hr, coincident with a sharp decline in TSH levels toward normal. In contrast, the high levels of LH declined much more slowly, failing to reach normal for as long as 7 weeks posttreatment.TSH in company with T4measurements permitted segregation of patients with Hashimoto's thyroiditis into three groups: (a) euthyroid with normal TSH and T4.

ISSN:0031-3998    

出版商:OVID    

年代:1973

数据来源: OVID

摘要:

ExtractHuman metaphase cells were treated sequentially with trypsin. Photographs of the cells stained before and during this treatment showed first Giemsa (G) banding then a gradual decrease in prominence of G bands and the appearance of C bands. These results were confirmed using computer-generated density curves.SpeculationThese results are more consistent with loss or change in configuration of chromosomal protein being the primary mechanism by which G and C bands are produced than denaturation-renaturation. Unless trypsin banding is carefully controlled a combination of G and C banding will be produced.

ISSN:0031-3998    

出版商:OVID    

年代:1973

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1973

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1973

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1973

数据来源: OVID