摘要:

ExtractTransintestinal intubation with a double lumen tubing was done on an infant with primary proximal renal tubular acidosis (PRTA), and in a comparative control patient with congenital hydrocephalus. The duodenum and first part of the jejunum were perfused at a rate of 2.5 ml/min with Krebs-Henseleit isotonic buffer containing 1 mM L-tyrosine and 20 mM D-glueose, with or without 30 mEq/liter bicarbonate (HCO3-). A nonabsorbable marker, polyethylene glycol (PEG), was added. All perfusate samples were measured for pH, partial pressure of carbon dioxide (pCO2), bicarbonate (HCO3-), osmolality, glucose, sodium (Na+), potassium (K+), chloride (Cl-), tyrosine, and PEG. In the PRTA patient, HCO3-lumen-to-blood fluxes were 0.9–1.42 μEq/min/cm of intestine as compared with 1.43–1.77 μEq/min/cm in the control patient. In contrast, the PRTA patient had a blood-to-lumen flux of HCO3-of 0.4 μEq/min/cm compared with 0.059 μEq/min/cm in the control patient. This difference in HCO3-secretion occurred while the PRTA patient's serum HCO3-level was 11.8–12.5 mEq/liter and that of the control subject was normal. Moreover, when the blood HCO3-levels of the PRTA patient were increased to 19–20 mEq/liter by intravenous administration of HCO3-the intestinal secretion of this anion increased to 2.4 μEq/min/cm. This could account for a total HCO3-loss of 5,000–10,000 μEq/min/cm intestine. The massive secretion of HCO3-in the upper segments of the small intestine in PRTA was associated with an adequate reduction in pCO2levels of the perfusates but with a defective Cl-secretory mechanism.SpeculationThere may be a defective Cl-/HCO3-“pump” in PRTA patients in the intestinal mucosa and renal tubule which enables them to secrete large quantities of bicarbonate in the upper segments of the small intestine and in the renal tubule. This may result from an impairment in Cl-secretory mechanisms since they are able to secrete hydrogen ion (H+) in a normal fashion. The quantitative loss of HCO3-in the upper segments of the small intestine in PRTA patients is more significant than that occurring through the kidneys, and it may play a very important role in the pathogenic processes of this entity.

ISSN:0031-3998    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

ExtractThe development of estrogen-mediated luteinizing hormone (LH) release (positive feedback) was studied in prepubertal, pubertal, and adult females. The optimum means of eliciting positive feedback was established by administering graded doses of 17β-estradiol (E2) for 5 days to 11 women during the early follicular phase of 14 menstrual cycles. Three groups of adult subjects were formed based on the peak levels of E2in plasma attained: 100–200 pg/ml, 200–300 pg/ml, and >300 pg/ml. In all groups, LH values in plasma fell to a nadir at a mean time of 2 days after the initiation of injections and then rose sharply while plasma E2levels in plasma still remained elevated. The magnitude of the LH elevations appeared to relate to the levels of E2in plasma.In contrast to the results in adult women, three prepubertal girls and an 11-year-old girl with gonadal dysgenesis did not evidence positive feedback when given similar estrogen courses. Levels of E2in plasma in the prepubertal subjects ranged between 100 and 300 pg/ml and both LH and follicle-stimulating hormone (FSH) remained suppressed. One early pubertal girl displayed a small increment in LH in the presence of elevated exogenous estrogen levels. One midpubertal, premenarchal girl with adult levels of gonadotropins and precocious puberty due to an hypothalamic cyst revealed a large LH rise during E2administration both before and after drainage of the cyst. Finally, a 14-year-old girl with gonadal dysgenesis and adult castrate levels of gonadotropins also displayed positive feedback.SpeculationPuberty in women is a multistage process which involves alterations in the hypothalamic-pituitary-gonadal axis. A change in sensitivity of the negative feedback system is associated with rising gonadotropin levels early in the course of sexual maturation. Ovulatory potential is dependent on the development of positive feedback, an event which occurs later in the course of pubescence.

ISSN:0031-3998    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

ExtractAmniotic fluid obtained transabdominally for prenatal diagnosis (mean length of amenorrhea 16.1 weeks) contained between 10 and 10 cells/ml, the great majority of which were squamous; their labeling index with ( H)thymidine was < 2 ± 10-3. An average of 3.5 clones ( > 10 cells)/ml fluid grew; of these, an average of 1.5 grew for >20 population doublings (CPD). Of 288 clones analyzed from 20 cases, 271 could be classified into one of three groups:group I, 24 were typical fibroblast-like cells (F cells) comparable with control clones from neonatal dermis with macroscopic “ribbing” growth pattern of megaclones, preponderance of spindle-shaped cells growing in parallel arrays, and high growth potential (mean of selected clones = 53 CPD);group II, 67 were typical epithelioid types (E cells) consisting of cells with intimate cell-to-cell contact which were resistant to trypsin detachment, with poor subcloning efficiencies and poor growth potential (mean of selected clones 14.5 CPD);group III, the predominant class with 180 clones, was of a type not described previously (AF cells); their megaclones had “bulls-eye” growth patterns, individual cells were pleomorphic, and growth potentials were intermediate to those of E and F cells. This tripartite classification holds for the majority of samples, but individual variation is suggested by the observation of exceptional clonal types sharing characteristics of both the E and AF class.SpeculationThe AF cell is the predominant type in most diagnostic amniotic fluid cultures; heretofore, such cultures were widely regarded as consisting primarily of fibroblast and epithelial-like cells. Skin fibroblast cultures are therefore inappropriate controls for the interpretation of constitutive and induced levels of enzymes in such cultures. Established amniotic fluid cell cultures are derived from a single or a few clonable cells with high growth potential and therefore may not always be representative of the fetus.

ISSN:0031-3998    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

ExtractFragments of testicular tissue from seven human fetuses were explanted in three organ-culture dishes for each fetus. One remained unirradiated while the others were submitted to, respectively, 500 and 700 rads of6 0Co γ-rays. After an interval of 1–2 weeks, the müllerian-inhibiting activity of the explants was tested using the 14 0.5-day-old rat miillerian duct as end organ and the number of germ cells present in 50 orthogonal sections of seminiferous tubules was determined on a minimum of 10 histologic sections. In control explants, only 12.9% of the original number of germ cells were normal after 1–2 weeksin vitro.The mortality of germ cells was increased by γ-rays; only 7% of their original number surviving 500 rads, and 3% 700 rads. Müllerian-inhibiting activity of both control and irradiated explants was normal.SpeculationMüllerian-inhibiting activity of human fetal testicular explants is not affected either by in vitro survival or by γ-irradiation, although both these procedures significantly deplete the germ cell population of the seminiferous tubules, only 3% surviving exposure to 700 rads. If germ cells were involved in the secretion of the antimüllerian hormone, such a drastic reduction of their number would certainly be reflected by an impairment of the müllerian-inhibiting activity of the irradiated explants. As this is not the case, and as it has been demonstrated previously that the antimüllerian hormone is synthesized by seminiferous tubules and not by interstitial tissue, we speculate that Sertoli cells are the source of the hormone.

ISSN:0031-3998    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

ExtractThe developmental pattern of the glomerular filtration rate (GFR), the regional glomerular density, and glomerular blood flow, as well as that of the cardiac output, blood pressure, and hematocrit has been followed in 2—79-day-old lambs. The glomerular perfusion rate (GPR),i.e., the glomerular blood flow, has been derived by determining the regional renal blood flow with microspheres and dividing it by the number of glomeruli per unit of renal tissue at that cortical depth assuming that practically all of the spheres are trapped in the glomeruli. The GFR per gram of renal tissue increased more rapidly during the first days of life, whereas the total GFR appeared to increase more linearly with age. The glomerular density fell in all cortical layers. The fall was slightly more pronounced in the inner cortex. The glomerular blood flow was recorded in three zones: the outer 10% of the cortex, which contained an aglomerular as well as a high density glomerular zone; the mid 65% of the cortex, which on gross inspection appeared fairly homogeneous; and the inner 25% of the cortex, which corresponded to the juxtamedullary zone. In all zones the GPR increased with age. The increase was most pronounced in the inner cortex in the oldest animals. The largest scatter of data was found in the outer cortex as a result of the heterogeneity of that zone. The cortical profile for the GPR did not change much with age, which indicated that in the lamb no intrarenal redistribution of blood flow of greater importance occurs during the postnatal development. In the inner and midcortex the GPR increased in proportion to the cardiac output. In the outer cortex the data indicate that GPR increased somewhat more rapidly than cardiac output.

ISSN:0031-3998    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

ExtractThe patterns of development of intestinal and hepatic fructokinase have been studied in the rat, in the rabbit, and in man, and information regarding the mechanism of control of this enzyme in mature organs has been obtained. Fructokinase activity was detectable 4 days before term in fetal rat jejunum (1.0 nmol/min/mg protein) and rose progressively to a plateau 20-fold greater by the 20th day of life (20 nmol/min/mg protein). The enzyme in rat ileum and liver and in rabbit liver behaved similarly (rising from 0.5 to 4.0 nmol/min/mg protein (ileum) and from 0.5 to 8.5 nmol/min/mg protein (liver)). In human fetal liver, there was a threefold rise in fructokinase activity from approximately the 10th to 24th week of gestation (increasing from 2.1 to 7.8 nmol/min/mg protein); jejunal activity rose slightly, but not significantly, during this period. As expected, feeding of mature rats with sucrose after prolonged carbohydrate starvation led to a twofold increase in jejunal (from 6.05 to 13.0 nmol/min/mg protein) and hepatic (from 14.1 to 24.2 nmol/min/mg protein) fructokinase activity. The administration of actinomycin before the introduction of sucrose inhibited the carbohydrate-stimulated rise in fructokinase activity in both organs. Similarly, injection of actinomycin during sucrose feeding produced a significant fall in enzyme activity which greatly exceeded that produced by fasting alone. The data suggest that the substrate-dependent activity of this enzyme may be regulated at the level of transcription.SpeculationThese studies support the hypothesis that the genetic control of certain enzymes involved in carbohydrate metabolism can be influenced by exogenous factors, among them dietary carbohydrate.

ISSN:0031-3998    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

ExtractRibosomal and cell sap fractions were prepared from first and third trimester human placentas. High endogenous activity was observed with ribosomes prepared from first trimester or third trimester placenta when incubated either in the presence of cell sap derived from first trimester placenta tissue or from Krebs II ascites tumor cells. The homologous placental system is capable of translating poly(U) and globin mRNA, although the latter is translated at about 10% of the efficiency as observed in the homologous ascites tumor system. The placental cell sap may be deficient in a factor necessary for the translation of globin mRNA. The preparation of active ribosomes from first and third trimester polysomes shows that it will be possible to study the endogenous synthesis of placental proteins throughout pregnancy.SpeculationThese results indicate the feasibility of studying the cell-free synthesis of placental peptide hormones. Human chorionic gonadotropin and human placental lactogen reach peak levels of synthesis at different gestational periods and thus the relation between the synthesis of the hormones and their secretion can be elucidated.

ISSN:0031-3998    

出版商:OVID    

年代:1974

数据来源: OVID

摘要:

ExtractFirst trimester placental lysosomes may play an important role in specialized physiologic events which occur in early gestation: endometrial invasion, cellular differentiation, and rapid organ growth. Placental tissue is readily separated from contaminating tissues and the syncytium is a source rich in lysosomes. Based on sedimentation velocity analysis, two lysosome “populations” are separated, each of which shows bimodal density distribution after isopycnic ultracentrifugation. Compared with term placental lysososmes, first trimester lysosomes are of lower buoyant density. First trimester placentas yield lysosome fractions with greater, specific activities for acid hydrolases than comparable subcellular fractions from term placenta. This correlates well with the postulated participation of the organelle in early placental processes.SpeculationPlacenta participates in many highly specialized processes in which the lysosome is hypothesized to be critical. Investigations on different tissues indicate that the incorporation of estrogens into lysosomal membranes alters organelle stability, thus possibly constituting a control mechanism of organelle function. The lower buoyant density of first trimester placental lysosomes may be indicative of differences in the lipid composition, possibly in membranes, and hence stability. The increased acid hydrolase activities of first trimester placental lysosomes point to similar control mechanisms in the trophoblast. Elucidation of these lysosomal functions will contribute to the understanding of processes operative in normal and neoplastic cellular growth.

ISSN:0031-3998    

出版商:OVID    

年代:1974

数据来源: OVID