[Regression analysis of the relationship between the birth rate and proportion of first order births in 1981].
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Asia↗
Biomedical subjects
S Chen
Publications and source records attributed to S Chen.
Reciprocal relationship between size of postsynaptic densities and their number: constancy in contact area.
Plasticity in the size of postsynaptic membrane specializations (postsynaptic densities) was analyzed by quantitation following lesioning of parallel fiber afferent axons to Purkinje cells in the cerebellum. Double sectioning of parallel fibers in the same folium as well as longitudinal undercutting of the molecular layer to destroy granule cells and their parallel fibers were used to produce various levels of afferent reduction to Purkinje cells. The length of profiles of membrane densities was measured utilizing semi-automated, computer-electron microscopy and the number of synapses was determined from their volume density and changes in volume estimated from cortical thickness. Correlation between the number of synapses on Purkinje cells and their average contacts area revealed a reciprocal relationship throughout a range of 0-67% reductions in parallel fiber synapses. Larger reduction levels had a progressive decrease in average size of contacted postsynaptic densities and an accompanying increase in the number of vacant postsynaptic specializations. Total absence of parallel fibers resulted in nearly all vacant sites on spines (except for a few connections with boutons having irregular shaped vesicles). These vacant sites were, on the average, only half the size of controls but their number was approximately double the control amount. This study confirms that location and size of synapses are not permanent and that plasticity in size of contacts allows reorganization in circuitry to compensate alterations in the number of inputs following a number of perturbations. The finding of a reciprocal relationship indicates that total contact area on Purkinje cells remained relatively constant throughout the entire range of reductions in the number of afferents. A 'constancy principle for total postsynaptic contact area' is envisioned to stabilize functional aspects of circuitry during developmental organization and to direct compensation following reduction in pre- or postsynaptic neurons from environmental effects or attrition in aging. Constancy in target area provides a realm under which the size of individual synapses can be modified as functional adaptations in circuitry even without changes in the number of connections.
Animals↗
Ultrastructural study of the effects of fixation and fluoride injection on stippled material during amelogenesis in the rat.
Perfusion with a variety of commonly-used fixatives was used. Quality of cell preservation and occurrence of stippled material between the mineralization front and the secretory ameloblasts were compared in normal animals and in ones injected with fluoride. There was no relationship between the formation of stippled material and the ultrastructural preservation of the cells. However, some types of fixatives were more likely than others to reveal the presence of stippled material in normal specimens. Most animals receiving fluoride showed substantial accumulations of stippled material, irrespective of the fixative used.
Amelogenesis↗
SV40 transformation of Swiss 3T3 cells can cause a stable reduction in the calcium requirement for growth.
A well-characterized SV40-transformed Swiss 3T3 line, SV101, and its revertants were tested for the ability to grow in reduced Ca++ (0.01 mM). Transformants and revertants did not differ from the parent 3T3 line in their Ca++ requirements. All three classes of cells grew less well in low Ca++ than in regular Ca++ (2.0 mM). SV40 transformants were then selected for the ability to grow in reduced Ca++. This new class of transformants was found to grow in 1% serum, grow in soft agarose, have a reorganized actin cytoskeleton, and express viral T antigens, as well as grow well in low Ca++. One of the selected clones was found to be T antigen-negative, yet was transformed in the serum, anchorage, actin, and Ca++ assays. It is possible that this clone was a spontaneous transformant. However, Southern blot analysis revealed the presence of integrated SV40 DNA. In addition, this analysis revealed the absence of an intact early region fragment, which codes for the viral T antigens. One explanation of this result may be that the mechanism of viral transformation for growth in low Ca++ involves viral-host DNA interactions that may not require a fully functional T antigen. In this case SV40 integration may be acting as a nonspecific cellular mutagen.
Animals↗
Interaction of N-(2-nitro-4-azidophenyl)-serotonin with two types of monoamine oxidase in rat brain.
The effects of N-(2-nitro-4-azidophenyl) serotonin (NAP-5-HT) on types A and B monoamine oxidase (MAO) in rat brain cortex were studied. In the dark this compound acted as a competitive inhibitor for both types A and B MAO (Ki values of 0.19 microM and 0.21 microM for types A and B MAO, respectively). Upon photolysis, NAP-5-HT became an irreversible inhibitor for only type B MAO. A 50% inhibition was obtained by irradiation of the enzyme in the presence of 35 nM NAP-5-HT. Furthermore the inhibition of type B MAO could be protected by including its substrate phenylethylamine during the irradiation. Under the same photolytic conditions photodependent inhibition of type A MAO by NAP-5-HT was not clearly observed. These results provide further evidence that there is a fundamental difference in the active site of the two types of MAO in brain. NAP-5-HT may be a useful photoaffinity probe for characterizing the active site of type B MAO.
Affinity Labels↗
DNase I sensitivity of integrated simian virus 40 DNA.
We undertook an analysis of integrated simian virus 40 (SV40) DNA to learn whether the DNase I-sensitive region is retained in the integrated array of mouse transformants. Our results indicate that full-length integrated SV40 chromatin retains a DNase I-hypersensitive region at the same point as in nonintegrated SV40 chromatin. Thus, the lack of a DNase I-hypersensitive region is not likely to be the reason for nonpermissivity of SV40 in mouse cells. In addition, results reported here indicate that a deletion of about 200 base pairs of DNA in the region of the DNase I-hypersensitive site severely reduces the sensitivity of integrated SV40 chromatin. This result is similar to a previously reported result obtained with deletion mutants of SV40 analyzed in the lytic cycle. It is the first report of a DNA lesion affecting DNase I hypersensitivity of a mammalian chromosome.
Animals↗
Reacquisition of a functional early region by a mouse transformant containing only defective simian virus 40 DNA.
Viral DNA in simian virus 40-transformed mouse cells is capable of rearranging with passage. In this report, we show that such rearrangement can include an alteration in viral protein expression. SVT2, a simian virus 40-transformed mouse BALB/c 3T3 cell line, synthesizes only a super T antigen of molecular weight 100,000 without synthesizing the lytic-size large T or small t antigens with molecular weights of 94,000 and 17,000, respectively. Analyses of the integrated viral DNA revealed an early region of 4.4 kilobases instead of the lytic-size 2.7 kilobases. However, upon subcloning in either plastic or agarose or after being in culture for several passages, the appearance of lytic-size large T and small t antigens was detected. Concurrently, an early region of 2.7 kilobases, in addition to one of 4.4 kilobases, was observed.
Antigens, Viral, Tumor↗
Evidence for the role of PO4 deficiency in antihypertensive action of a high-Ca diet.
Previous studies indicated a salutary effect of a high-Ca diet on high blood pressure (BP). The mechanism, however, is obscure. With balance and clearance techniques, the role of parathyroid hormone (PTH), volume contraction, hypercalcemia, and PO4 deficiency was evaluated in female spontaneous hypertensive rats (SHR). The antihypertensive effects of a high (4.3%) Ca diet in intact animals (groups I and II) could be reproduced in both 9- and 22-wk-old chronic stable parathyroidectomized (PTX) rats (groups III and IV), when compared with a low (0.22%) or normal (1.2%) CA diet. In both short (7 days) and long (12 wk) term exposure to the high-Ca diet, evidence for volume contraction could not be documented despite hypercalcemia sustained through the 12th wk (10.8 vs. 9.7 mg/100 ml, group I control, P less than 0.02). When produced by ip injections, chronic hypercalcemia of similar magnitudes as oral Ca supplements failed to reduce BP in either intact (group VI) or PTX (group IV) rats. Rats in group IV fed the high-Ca diet displayed marked hypophosphatemia (3.2 vs. 6.9 mg/100 ml), hypophosphaturia (0.15 vs. 15 mg/day), hypermagnesiuria (11 vs. 7.7 mg/day), and drastically reduced net intestinal PO4 absorption (13.3 +/- 7.5 vs. 66.8 +/- 7.5 mg/day) compared with rats fed 1.2% Ca diet. To test the PO4-deficiency hypothesis, additional SHR (group V) were fed either 1.2% Ca diet and injected ip with NaCl or fed 4.3% Ca diet, with half of these animals injected with neutral NaPO4 and half with NaCl.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Scanning electron microscopy of cultured human megakaryocytes.
Human megakaryocytes (MK) from rib marrows of 16 patients with normal hematological patterns were isolated by Percoll density centrifugation followed by velocity sedimentation. The surface features of freshly isolated MK and the unseparated marrow suspensions were examined by SEM. A wide range of surface morphology for MK was noted depending on their size and maturation stages. Megakaryoblasts had a relatively smooth surface. During maturation, MK became villous and some had small blebs. In late maturation, many MK had complex surface processes including typical discs, slightly sphered projections, tear drop projections, putative sheet-like platelets or combinations of two or more of such surface features. Both unseparated and MK-rich fractions (F); specifically F1 lower, F2 lower and F3 were cultured up to 19 days. MK maintained their spherical shape in culture. At different time intervals (2, 5, 9 and 19 days), some cultures were terminated. MK retained their characteristic surface features. Promegakaryocytes and young adult MK were seen in short term cultures. The majority of cultured MK had platelet-like bodies on their surface in the prolonged cultures. Sometimes a few morphologically recognizable platelets were seen in the culture media. Differential counts of MK were done in all preparations of both unseparated and MK enriched fractions. F3, having no morphologically recognizable MK, had many MK present after culturing in vitro for 19 days. These MK had typical platelets or platelet-like processes on their surface. This suggests some MK progenitors originally present in the isolated F3 fraction became mature in cultures.
Bone Marrow↗
Differences in chromatin from normal and leukemic human cells as shown by digestion with restriction nucleases.
Restriction endonuclease MspI digested significantly more than HpaII the DNA and chromatin from normal and leukemic human cells, although both enzymes digested DNA more than chromatin. Moreover, DNA and chromatin from normal cells showed higher digestion by HpaII compared to DNA and chromatin from leukemic cells indicating higher frequency of Cm5CCG in latter DNA. EcoRII and BstNI, which have the recognition sequence CCATGG but cut at different points, digested all DNAs significantly, as did BstNI for chromatin from all sources. However, chromatin from normal cells showed only limited digestion by EcoRII which significantly digested chromatin from leukemic cells. This could result from subtle differences in the conformation of normal and leukemic cell chromatin involving recognition sequences for EcoRII.
Chromatin↗
[The present task of family planning as suggested by the findings of the National Sample Survey of Fertility].
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Asia↗
DDAVP: does the drug have a direct effect on the vessel wall?
Evidence is presented that 1-deamino-8-d-arginine vasopressin (DDAVP), a vasopressin analog, has a direct effect on isolated vessel segments. The most significant finding is increased platelet adhesion and spreading at injury sites. An isologous human umbilical vein perfusion model was used to compare effects of DDAVP with those of epinephrine or zero drug controls. Scanning electron microscopy, in conjunction with morphometry, permitted quantification of platelet adhesion to subendothelium exposed by minimal injury in the model. In addition, umbilical vein effluents were tested for levels of factor VIII moieties (F VIII:C, F VIII:Rag, F VIII:RCof) and the prostanoids, 6 keto PGF1 alpha (stable metabolite of prostacyclin) and TXB2 (stable metabolite of thromboxane A2. Only F VIII:C from DDAVP treated segments was significantly (p less than 0.01) changed from controls.
6-Ketoprostaglandin F1 alpha↗
Integration, loss, and reacquisition of defective viral DNA in SV40-transformed mouse cell lines.
We have examined the state of viral DNA in a set of SV40-transformed mouse cell lines. Using restriction enzymes which cut SV40 DNA in one place, we demonstrate that anchorage-independent SV40-transformed mouse cells commonly contain one or more detectable defective monomers of integrated viral DNA. The defective viral DNA in one of these cell lines, SV101, was extensively mapped using single and double enzyme digests. The results of this analysis indicate that SV101 contains nondefective viral DNA as well as defective viral DNA of the following sizes: 5.0, 4.3, 3.7, 3.4, and 1.5 kb. Three of these defective monomers (4.3, 3.7, and 1.5 kb) preserve the amino terminal exon of large T antigen, and two monomers (4.3, and 3.7 kb) preserve the little t coding region. Anchorage-dependent subclones of SV101 preferentially lose the defective viral DNA, while retaining an intact SV40 early region and the ability to express lytic-sized large and small T antigens. Despite a considerable amount of viral DNA rearrangement which accompanies subcloning, anchorage-independent subclones of SV101 retain defective viral DNA, especially the 4.3- and 3.7-kb monomers. Also, when an anchorage-independent subclone is selected from an anchorage-dependent revertant of SV101, it reacquires defective viral DNA, although of a size not seen in SV101. We conclude that defective viral DNA plays a role in generating the anchorage-independent phenotype. In earlier studies, we have reported that anchorage-transformed mouse lines contain a variant (100kDa) T antigen. The possible role of defective viral DNA in generating this T antigen is discussed.
Animals↗
Duct-obliterated canine pancreatic segmental transplantation.
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Amylases↗
Pre-crisis mouse cells show strain-specific covariation in the amount of 54-kilodalton phosphoprotein and in susceptibility to transformation by simian virus 40.
We have used several inbred mouse strains to examine the role of the 54-kilodalton (kDa) cellular phosphoprotein in transformation by the papovavirus simian virus 40. We have measured the endogenous 54-kDa phosphoprotein in cells obtained from these inbred mouse strains. To study the effect of passage, cell cultures were measured for amount of the 54-kDa phosphoprotein at the 2nd and 12th passages. In the absence of any transforming agent, the amount of endogenous 54-kDa phosphoprotein in early pre-crisis mouse cells varied in a strain-specific way. Transformation frequency varied coordinately with endogenous 54-kDa expression. Mouse strains whose cells produced a high level of endogenous 54-kDa phosphoprotein on passage did not further increase its expression after simian virus 40 transformation.
Animals↗
A frameshift mutation affecting the carboxyl terminus of the simian virus 40 large tumor antigen results in a replication- and transformation-defective virus.
We have constructed a frameshift mutation in the simian virus 40 early region using a novel method of oligonucleotide-directed mutagenesis. The mutated DNA specifies an 84,000-dalton large tumor antigen that consists of approximately equal to 75,000 daltons encoded by the wild-type reading frame and 9,000 daltons, by the alternative reading frame (wild-type large tumor antigen is approximately equal to 82,000 daltons). The frameshifted carboxyl terminus of the protein bears a strong similarity to the same region of polyoma virus middle-sized tumor antigen. We have found that the mutant DNA is unable to replicate when introduced into permissive monkey cells and incapable of transforming nonpermissive mouse cells.
Amino Acid Sequence↗
Effects of temperature on arachidonic acid-induced cellular edema and membrane perturbation in rat brain cortical slices.
The effects of temperature on arachidonic acid-induced cellular edema in the first cortical brain slices of rats were studied. Incubation of the cortical slice in arachidonic acid at 37 degrees C induced cellular swelling, and increased intracellular Na+ and lactic acid contents concomitant with decreased intracellular K+. When the incubation temperature was reduced these changes were reduced in severity. The uptake of [3H]arachidonic acid in cortical slices was temperature-dependent. The incorporation of [3H]arachidonic acid into various lipid fractions was further studied by HPLC. The majority of [3H]arachidonic acid was incorporated into triacylglycerol and phosphatidylinositol (PI), but the incorporation of [3H]arachidonic acid into PI was temperature-dependent, unlike that into other phospholipids and neutrolipids. Further, cortical (Na+ + K+)-ATPase activity was inhibited whereas its subunit K+-activated p-nitrophenyl-phosphatase was activated by arachidonic acid at various incubation temperatures. The effects of arachidonic acid on these enzymes is similar to that of thimerosal, a lipid removal agent. These data suggest that both temperature and arachidonic acid play an important role in the development of cellular edema associated with membrane perturbation and inactivation of (Na+ + K+)-ATPase activity.
4-Nitrophenylphosphatase↗
A functional simian virus 40 origin of replication is required for the generation of a super T antigen with a molecular weight of 100,000 in transformed mouse cells.
We used two recombinant plasmids, one containing wild-type simian virus 40 DNA (pSVR1) and the other containing a simian virus 40 genome with a defective origin of replication (pSVR1-origin-minus) to transfect NIH3T3 cells. Quantitation of T-antigen synthesis by indirect immunofluorescence at 48 h after transfection with either DNA revealed the same percentage of T-positive nuclei. The transformation frequencies observed were also similar with both plasmids. Immunoprecipitation of [35S]methionine-labeled cell extracts showed the expected 94,000-dalton (94K) T and 17K t antigens in all clones examined. In pSVR1-generated transformants, a 100K super T antigen was also detected. Transformants isolated from pSVR1-origin-minus transfection, however, never expressed this 100K super T antigen, and some of these clones originally also showed greatly reduced levels of 94K T antigen. However, after growth in culture for several generations, the levels of 94K T antigen synthesis in these underproducer clones were dramatically increased. A direct correlation between the amounts of T antigen synthesized and the ability to grow independently of anchorage was observed. The mechanism which brings about increasing levels of T-antigen synthesis in some of the clones is not clear, but it appears not to be due to changes in either the copy number or the methylation pattern of the integrated simian virus 40 DNA.
Animals↗