Reappraisal of effective refractory period testing

To test the hypothesis that effective refractory period (ERP) testing is an accurate and reproducible measure of the cardiac refractory period, 4 pigs and 12 dogs were studied. We define the conventional ERP as the longest S1-S2 interval associated with noncapture and the triplicate ERP as the average of three ERP values determined by the up-down algorithm. We also determined the probability curve for noncapture after testing multiple S1-S2 intervals. The results showed that the difference between the coupling intervals associated with a 0 and a 100% probability of noncapture was 13 +/- 1 (range 12-16) ms for pigs and 9 +/- 2 (range 4-12) ms for dogs. The conventional and the triplicate ERP were associated with a 71 +/- 20% (range 26-100%) and a 60 +/- 21% (range 12-100%) probability of noncapture, respectively. We conclude that the ERP is a probability function. Therefore a single ERP determination cannot be used as an accurate and reproducible measure of cardiac refractory period unless it is used to detect potential differences in ERP that exceed 16 ms in pigs or 12 ms in dogs. A probability function curve determination will be needed if smaller differences in the ERP are to be detected.

Nylestriol replacement therapy in postmenopausal women. A three-year prospective study

A three-year prospective study was carried out in 283 postmenopausal women to evaluate the effects of a long-acting estriol derivative-nylestriol. The women were randomly assigned into 3 groups: group A (136 cases, nylestriol 2 mg/2 wk), group B (97, nylestriol 1 mg/2 wk) and group C (50, placebo/2wk). LDL-C decreased and HDL-C increased after 3 months of medication (P < 0.05), but TC and TG not significantly changed in any group (P > 0.05). No changes of lipids were found in group C (P > 0.05). Serum ALP, Ca/Cr and Hpr/Cr in fasting urine decreased in 3 months in both group A and B (P < 0.05), but not in group C (P > 0.05). Forearm bone mineral content loss was restrained in groups A and B (P > 0.05), but decreased markedly in group C (P < 0.01). The Kupperman index scores decreased by about 50% after 3 months and 80% in 12 months in groups A and B. Nylestriol induced mild stimulatory effect on the uterine endometrium, and addition of 6 mg of provera daily for 7-10 days every 6 months is recommended. Nylestriol exhibited no obvious effect on the breast. This study demonstrated that nylestriol can be used as an effective and acceptable estrogen replacement therapy for postmenopausal women.

Characterization of selective glucocorticoid-dependent responses in a glucocorticoid-resistant smooth muscle tumor cell line

The DDT1 MF2 smooth muscle cell line was derived from an estrogen/androgen-induced leiomyosarcoma arising in the hamster ductus deferens. Growth of this cell line is arrested in G0/G1 by treatment with glucocorticoids. To facilitate the study of the mechanism of glucocorticoid-induced cell growth arrest, a glucocorticoid-resistant variant cell line, DDT1 MF2 GR1 (GR1), was developed by genetic selection. Growth of this mutant cell line is completely resistant to the inhibitory action of glucocorticoids. However, we now demonstrate that both primary and secondary glucocorticoid-induced events still exist in the GR1 cell line. By analyzing the expression and genetic pattern of glucocorticoid receptor, no detectable rearrangement of the glucocorticoid receptor gene was found although the expression of both mRNA and protein levels of the receptor were lower in the variant compared to wild-type cells. In addition, we found that the expression of two growth-associated genes, Ha-ras and transforming growth factor beta 1 (TGF-beta 1) are down-regulated by glucocorticoids in wild-type DDT1 MF2 cells but not in GR1 cells. These results indicated that the function or activity of glucocorticoid receptor in the GR1 cells is not qualitatively altered. Our data suggest that a lower glucocorticoid receptor level is not the real cause or at least not the single cause for the GR1 cell's loss of sensitivity to the inhibitory action of glucocorticoid. Instead, we postulate the existence of a defect downstream of the primary site of action of glucocorticoid receptor complexes in GR1 cells.

Protein kinase C activity and its relationship to myo-inositol uptake during hyperglycemic conditions in cultured bovine lens epithelial cells

Incubation of cultured bovine lens epithelial cells (BLECs) in minimal essential medium (MEM) containing 40 mM galactose for 20 hr results in an attenuation of 3H-myo-inositol (3H-MI) concentrating ability. Decreased MI uptake could negatively impact on normal phosphoinositide turnover and diacylglycerol production, and presumably, protein kinase C (PKC) activation. The present report examines the relationship between PKC activity, myo-inositol transport and hyperglycemic conditions. PKC activities in the cytosol and particulate fractions of bovine lens epithelial cells in culture were quantitated using a mixed micelle assay following DEAE-cellulose (DE52) and Sephadex G-25 chromatography. Protein kinase C activity was assessed as Ca2+ and phospholipid-dependent Ac-myelin basic protein substrate peptide phosphorylation and confirmed using a PKC pseudosubstrate inhibitor peptide (PKC 19-36). Total PKC activity was similar in galactose-incubated cells (871 +/- 64 pmol/mg total protein/min) and control cells (881 +/- 8 pmol/mg total protein/min) after 20 hr. In unstimulated cells, approximately 90% of the total cellular PKC activity was recovered in the cytosolic fraction. Enzyme translocation was induced with the tumor promoting phorbol ester, phorbol 12-myristate 13-acetate (PMA), resulting in a 6-fold increase in membrane-associated PKC activity. A similar PMA-induced translocation was observed in BLECs incubated with 40 mM galactose MEM-maintained cells briefly treated with PMA or the non-phorbol PKC activators, SC-10 and mezerein, displayed a rate of 3H-MI uptake similar to the untreated control cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Localization of epidermal growth factor and its receptor in mandibular molars of the rat prior to and during prefunctional tooth eruption

Immunoperoxidase localization of epidermal growth factor receptors (EGFR) and epidermal growth factor (EGF) itself was examined in rat first and second mandibular molars postnatally from day 0 to 12. The results showed that the dental follicle stained heavily for EGFR from day 0 to 8, declined in staining at day 9, and was devoid of stain from day 10 onward. Preosteoblasts and osteoblasts of alveolar bone also stained and lesser staining of ameloblasts and odontoblasts was observed. Except for staining of occasional isolated cells, the stellate reticulum did not stain. Light staining of the dental pulp of the first mandibular molar was seen from day 0 onward but the pulp of the second molar did not stain until approximately day 6. With respect to EGF, the dental follicle also stained for it until day 12. The ameloblasts stained more intensely for EGF than for EGFR. Because injections of EGF cause premature eruption of teeth and because the presence of a dental follicle is necessary for eruption, this study suggests that EGF could have its effect on the follicle as seen by the presence of EGFR receptors on the follicle. Moreover, because EGF exerts its effects early (day 0-3) to cause eruption and because the influx of monocytes into the follicle to form osteoclasts for bone resorption for eruption occurs early, the heavy staining for EGFR in the follicle early followed by the absence of staining at day 10 correlates chronologically with the key molecular and cellular events of eruption. Finally, the presence of EGF in the follicle, as well as enamel organ, could provide an endogenous source of EGF to regulate tooth eruption, either by an autocrine or a paracrine effect. Thus, the localization of EGFR and EGF in the dental follicle coupled with the chronology of localization suggests that EGF could play a physiological role in tooth eruption.

Granule proteins of the dental follicle and stellate reticulum inhibit tooth eruption and eyelid opening in postnatal rats

Electron-dense granules within cells of the dental follicle and stellate reticulum of rat mandibular molars can be isolated; their major components are 167 and 200 kDa proteins. Injecting these granule proteins into postnatal rats results in a delay of incisor eruption and eyelid separation. These inhibitory effects were most pronounced with the 167 kDa protein (a delay of 3 days in incisor eruption and of 2 days in eyelid opening) and were opposite to the stimulatory effects of epidermal growth factor. Thus, these granules may play an inhibitory part in tooth eruption.

Isolation of granule proteins from cells of the dental follicle and stellate reticulum of rat mandibular molars

The presence of a dental follicle is required for eruption of teeth of limited eruption but it is uncertain if any molecules indigenous to the follicle regulate this eruption. However, electron-dense granules of unknown composition and function are present in the fibroblasts of the dental follicle of rat molars, as well as the adjacent stellate reticulum, before and during tooth eruption. Here the granules have been isolated; two proteins, of 167 and 200 kDa, have been determined by biochemical and immunological methods to be major components of the granules.

Widespread differentiation stage-specific expression of the gene encoding phosphoprotein p19 (metablastin) in mammalian cells

p19 is a highly conserved 19 kD cytosolic protein that undergoes phosphorylation in response to diverse extracellular factors in mammalian cells. Its expression is abundant in brain and testis and is developmentally regulated. To gain insights regarding its function, we analyzed the expression of p19 mRNA in a variety of cell types during induction of differentiation. Murine erythroleukemia cells showed a moderate increase followed by a marked decrease in the abundance of p19 mRNA during induction of differentiation. In murine C2 myoblasts and primary fetal rat osteoblasts, p19 mRNA was abundant in replicating cells and decreased to undetectable levels during differentiation. In resting human peripheral blood lymphocytes, p19 mRNA was virtually undetectable but was strongly induced during blast transformation of both B and T cells. In rat liver, p19 mRNA was abundant on embryonic day 17 and decreased during early postnatal development. Upon fractionation of adult rat liver cells by centrifugal elutriation, p19 mRNA was not detected in hepatocytes while a low level was observed in a fraction enriched in non-parenchymal epithelial cells. CCl4-induced liver regeneration resulted in induction of p19 mRNA in hepatocytes. Primary cultures of embryonic and neonatal rat brain were analyzed by indirect immunofluorescence using co-staining with stage-specific markers. p19 expression was restricted to immature neurons and oligodendrocyte precursors. In contrast to the other cell types examined, the neuronal and glial precursors that express p19 were shown, using BrdU labeling, to be postmitotic both in primary culture and in vivo. The data demonstrate widespread, stage-specific expression of p19 and suggest that the protein exerts a general, lineage-independent function during induction of differentiation of mammalian cells. In view of the available evidence on the stimulation of serine phosphorylation of p19 by several growth factors, our working hypothesis is that phosphorylation of p19 may be involved in the mechanism by which growth factors control cell differentiation.

Cloning of a mu-class glutathione S-transferase gene and identification of the glucocorticoid regulatory domains in its 5' flanking sequence

The expression of a mu-class glutathione S-transferase gene (hGSTYBX) isolated from hamster smooth muscle tumor cells (DDT1 MF-2) is transcriptionally up-regulated by glucocorticoids, and this hormonal regulation is dependent upon protein synthesis. To study the mechanism of regulation, we have cloned and sequenced hGSTYBX genomic DNA including its 5' flanking region. The hGSTYBX gene contains nine exons dispersed over a 6.3-kilobase region. When linked to a chloramphenicol acetyltransferase (CAT) reporter gene, the 5' flanking region was able to direct transcription of the reporter gene. With 5' deletion studies, we have localized the major glucocorticoid-inducible regulatory element between nucleotides -353 and -239. Within this region no classic glucocorticoid response element (TGTTCT) was identified, but four potential helix-loop-helix binding domains are embedded in two 16-base-pair repeats. Another glucocorticoid regulatory domain has been localized between nucleotides -239 and -136. Cycloheximide blocks glucocorticoid-induced transcription of both the -353CAT and -239CAT reporter genes (nucleotides -447 to -12 and nucleotides -239 to -12 of hGSTYBX, respectively, ligated to a CAT reporter gene); therefore, our observations support previous results suggesting that hGSTYBX induction by glucocorticoids is a secondary response.

Effects of transforming growth factor-beta 1 on cultured dental follicle cells from rat mandibular molars

Analysis of the total proteins secreted by cultured dental follicle cells revealed that transforming growth factor-beta 1 (TGF-beta 1) stimulated them to secrete more extracellular matrix proteins into a serum-free medium than did follicle cells not exposed to the growth factor. Electrophoresis and scanning densitometry showed that secretion of all the major proteins was increased by exposure to the growth factor but the amounts ranged from a 66% increase for one of the procollagen chains to a 7% increase for fibronectin. Immunofluorescence using anti-type I collagen and anti-fibronectin showed that the intracellular concentration and intracellular localization of the antibodies was not changed by incubating the cells with the growth factor. The growth factor did not cause an increase in cell number but did modify the association of the cells in the culture, causing them to aggregate into clusters whereas the control cells formed a confluent monolayer. These results suggest that TGF-beta 1 may signal the fibroblasts of the dental follicle to secrete the extracellular matrix needed for its development into a periodontal ligament.

Clinical manifestations and prevalence of different types of supraventricular tachycardia among Chinese

Sixty-nine cases of paroxysmal supraventricular tachycardia (PSVT) were submitted to electrophysiological studies. The prevalence of different types of PSVT is as follows: 49% of the cases had atrioventricular reentry tachycardia (AV-RT), 14.5% atrioventricular nodal reentry tachycardia (AVN-RT), 28% AV + AVN - RT, and 8.5% other types. Altogether 77% in this group had atrioventricular accessory pathway, of which half are concealed pathway. Electrocardiographic characteristics during tachycardia give hints to diagnosis: (1) AV - RT has the fastest heart rate, with 62% 200 BPM or more, and 82% more than 188 BPM; (2) retrograde P waves can be detected in 64% of cases with AV bypass; (3) 50% of AV - RT shows QRS of bundle branch block pattern. Since accessory pathways are present in the majority of PSVT patients in China, the importance of treatment is stressed.

Culture and characterization of dental follicle cells from rat molars

Because the dental follicle is necessary for the eruption of teeth of limited eruption, it was the objective of this study to determine if the cells of the follicle could be cultured in vitro. To achieve this, dental follicles and associated enamel organs were dissected from the first and second mandibular molars of 6-7-day-old rats (secretory stage of amelogenesis), and then cultured in a medium that promotes fibroblast growth--the predominant cell type of the dental follicle. The cultured cells grew to confluency and were kept through 3 passages before experimentation. The cultured cells were fibroblastic in shape, elongate with processes, and transmission electron microscopy revealed that they contained an abundant rough endoplasmic reticulum, but did not form desmosomes. Immunofluorescent staining for anti-vimentin showed that all the cells stained and electron-microscopic immunogold labeling indicated that the antibody was associated with intermediate filaments. As revealed by SDS-polyacrylamide gel electrophoresis and Western blotting, the cultured cells synthesized and secreted the extracellular matrix molecules fibronectin and procollagens. Subsequent immunofluorescence staining of permeabilized and non-permeabilized cells confirmed the presence of fibronectin and type I collagen both intra- and extracellularly. Thus, based on all the above characteristics, the cultured cells appeared to be fibroblasts derived from the dental follicle, although a few of the fibroblasts may be derived from undifferentiated mesenchymal cells interposed between the alveolar bone and follicle. Experiments now can be conducted to determine how these cultured cells respond directly to growth factors that alter the rates of tooth eruption.

Evidence for separate networks of classical and novel basement membrane collagen. Characterization of alpha 3(IV)-alport antigen heterodimer

The COOH-terminal non-collagenous domains (NC1) of type IV collagen from glomerular basement membranes (GBM), lens capsule basement membranes, and Descemet's membrane varied in the distribution of their NC1 subunits. All of these basement membranes (BMs) contained both classical (alpha 1(IV) and alpha 2(IV)) and novel collagen chains (alpha 3(IV), alpha 4(IV) and the Alport antigen). Whereas GBM had a predominance of disulfide-bonded subunits, the lens capsule and Descemet's membrane were primarily monomeric, differences that are likely related to the functional and structural diversity of collagen in various tissues. A heterodimer formed from monomeric subunits of alpha 3(IV) and the Alport antigen exists in human and bovine GBM. This dimer represents an important cross-link of the NC1 domain of novel collagen. Additionally, immunoaffinity methodology showed that the novel BM collagen hexamers segregate into populations containing only novel BM subunits without the participation of the classical subunits (alpha 1(IV) and alpha 2(IV)). These data provided evidence for the presence of two separate networks of BM collagen: one containing alpha 1(IV) and alpha 2(IV), and the other consisting of the novel collagen chains.

Differential mRNA expression of the phosphoprotein p19/SCG10 gene family in mouse preimplantation embryos, uterus, and placenta

The p19/SCG10 gene family encodes two structurally related cellular proteins that are implicated in signal transduction during differentiation of mammalian cells. Previous evidence suggests that both genes are expressed in a stage-specific manner but that expression of p19 is widespread, whereas that of SCG10 is restricted to developing neurons. To determine at which developmental stage these two genes are first expressed, we have probed for mRNA transcripts in preimplantation embryos and the utero-placental unit of the mouse. As determined by polymerase chain reaction (PCR) to amplify reverse-transcribed RNA, expression of both genes was detected in preimplantation embryos, although the temporal pattern was distinct. p19 mRNA appeared transiently in 2-cell embryos, was undetectable in morulae and early blastocysts and reappeared in expanded blastocysts. In contrast, embryonic expression of SCG10 mRNA commenced in morulae and was maintained through to the blastocyst stage. Interestingly, only SCG10 expression could be detected in blastocysts derived from cultures of 2-cell embryos. During the post-implantation period, SCG10 transcripts were only detected in the uterus and placenta by reverse transcriptase-PCR, whereas p19 mRNA could be detected by Northern blotting and showed stage-specific expression in both tissues. The data confirm that, at later developmental stages, expression of p19 is widespread while that of SCG10 is more restricted. The expression of both genes in preimplantation embryos suggests distinct but possibly overlapping roles for p19 and SCG10 in early mammalian development.

Multiple types of cytokines constitutively produced by an established murine thymic epithelial cell line

An untransformed murine thymic epithelial cell line (MTEC1) has been established. Without exogenous stimulation, the MTEC1 cells constitutively produced multiple types of cytokines, including IL-1, IL-6, IL-7, GM-CSF and chemotactic factor(s). Of which, IL-6, GM-CSF and chemotactic factor(s) were abundant; IL-1, moderate; and IL-7 at low level. MTEC1 cells neither produced detectable IL-3 nor TNF alpha. Thus, the MTEC1 cells may be useful not only in the evaluation of the signals required for thymic selection in vitro, but also useful in the analysis of the endogenous regulation of the autocrine cytokine production cascade.

Age-related changes in the clinical and electrophysiologic characteristics of patients with Wolff-Parkinson-White syndrome: comparative study between young and elderly patients

The natural history of patients with Wolff-Parkinson-White (WPW) syndrome remains an intriguing question with respect to clinical decision-making, since serial electrophysiologic data spread over several decades in the same patient are not available in the literature. To study the age-related changes in WPW syndrome, we compared two separate groups of patients referred to this Medical Center for electrophysiologic studies because of a clinical presentation with significant arrhythmias. An elderly group of 42 patients aged 50 years or more were compared with a younger group of 51 patients aged 15 to 30 years. The groups were comparable in terms of clinical presentation, including the number of patients who had reported syncopal episodes and those requiring cardioversion of their tachyarrhythmias. Baseline electrophysiologic variables such as sinus rate; sinoatrial conduction time; corrected sinus node recovery time; AH interval; and effective refractory periods of the right atrium, atrioventricular (AV) node, and right ventricular muscle, were significantly greater in the elderly group. Similarly, the anterograde effective refractory period of the bypass tract, the shortest atrial pacing cycle length with 1:1 anterograde conduction via the bypass tract, retrograde effective refractory period of the bypass tract, the shortest ventricular pacing cycle length with 1:1 retrograde conduction via the bypass tract, the shortest consecutive preexcited R-R interval during atrial fibrillation, and the cycle length of orthodromic atrial ventricular reciprocating tachycardia were significantly greater in the elderly group.(ABSTRACT TRUNCATED AT 250 WORDS)

Eosin Y staining of proteins in polyacrylamide gels

A staining method is described in which various proteins in polyacrylamide gels can be stained by using eosin Y. After a brief incubation of a polyacrylamide gel in an acidic solution of 1% eosin Y, various proteins, including human erythrocyte membrane sialoglycoproteins which are not detectable by Coomassie blue R-250 (CB), can be detected with a sensitivity of 10 ng protein. This is far more sensitive than CB staining and is comparable to the sensitivity of silver staining. In a Western blot, the antigenicity of an eosin Y stained protein is retained. In addition, proteins on an immunoblot sheet can be detected by eosin Y staining. The method described is rapid, sensitive, and reproducible with various proteins in polyacrylamide gels and has the added advantage of also staining sialoglycoproteins.

Immunolocalization of transforming growth factor beta in rat molars

A prominent cellular event in tooth eruption is the influx of mononuclear cells (monocytes?) into the dental follicle at the onset of eruption. In the mandibular first molar of the rat, this influx of cells reaches its peak at three days postnatally. Because transforming growth factor-beta 1 (TGF-beta 1) is chemotactic for monocytes, we used immunocytochemical methods to determine its localization in the rat molar during postnatal days 1-4 and day 7. The results indicate that TGF-beta 1 displays both a spatial and temporal localization in the rat molar. It is present in the stellate reticulum (SR) on days 1 and 2 postnatally but is absent in all the subsequent days examined. None of the other soft tissue layers-ameloblasts, stratum intermedium or dental follicle--immunostain for TGF-beta 1. This localization of TGF-beta 1 in the SR at a time that just precedes that influx of monocytes into the dental follicle, coupled with the fact that fenestrated capillaries are abundant in the follicle adjacent to the SR, suggests that TGF-beta 1 could play a role in attracting monocytes from the peripheral blood into the follicle.