CT features of abdominal manifestations of primary antiphospholipid syndrome

PURPOSE

The purpose of this work was to evaluate the CT features of the abdominal manifestations of primary antiphospholipid syndrome (PAPS).

METHOD

Of the 32 patients who were confirmed to have PAPS among 751 patients with elevated antiphospholipid antibodies during a 2 year period, we retrospectively reviewed the 14 patients who underwent abdominal CT. The clinical indications for abdominal CT included abdominal pain, abdominal distension, or lower leg swelling. CT findings were analyzed with regard to the abdominal vascular system and abdominal organ involvement patterns as well as ancillary findings.

RESULTS

Of the 14 patients with PAPS, 10 had involvement of the venous system (72%), 2 of the arterial system (14%), and 2 of both systems (14%). Of the 12 patients who had venous system involvement, 4 had thrombosis in the inferior vena cava (IVC), 2 in both the IVC and the hepatic vein, 1 in the IVC and splenic and portal veins, 1 in the IVC and hepatic and adrenal veins, 1 in the hepatic, portal, and renal veins, and 3 in the portal and superior mesenteric veins. Budd-Chiari syndrome developed in five of the nine patients who had thrombosis of the IVC or hepatic vein. Arterial thrombosis was noted in four patients, hepatic artery in two, aorta in one, renal artery in one, pancreatic arcade in one, and splenic artery in one, with infarct of multiple organs including the liver, jejunum, colon, kidney, and adrenal gland. Seven of the 14 patients (50%) manifested thrombosis or infarct of multiple extra-abdominal organs.

CONCLUSION

PAPS should be included in the differential diagnosis when CT demonstrates infarcts in multiple organs or patients have recurrent episodes of venous or arterial thrombosis.

The mechanism of rhythmic ethylene production in sorghum. The role of phytochrome B and simulated shading

Mutant sorghum (Sorghum bicolor [L.] Moench) deficient in functional phytochrome B exhibits reduced photoperiodic sensitivity and constitutively expresses a shade-avoidance phenotype. Under relatively bright, high red:far-red light, ethylene production by seedlings of wild-type and phytochrome B-mutant cultivars progresses through cycles in a circadian rhythm; however, the phytochrome B mutant produces ethylene peaks with approximately 10 times the amplitude of the wild type. Time-course northern blots show that the mutant's abundance of the 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase mRNA SbACO2 is cyclic and is commensurate with ethylene production, and that ACC oxidase activity follows the same pattern. Both SbACO2 abundance and ACC oxidase activity in the wild-type plant are very low under this regimen. ACC levels in the two cultivars did not demonstrate fluctuations coincident with the ethylene produced. Simulated shading caused the wild-type plant to mimic the phenotype of the mutant and to produce high amplitude rhythms of ethylene evolution. The circadian feature of the ethylene cycle is conditionally present in the mutant and absent in the wild-type plant under simulated shading. SbACO2 abundance in both cultivars demonstrates a high-amplitude diurnal cycle under these conditions; however, ACC oxidase activity, although elevated, does not exhibit a clear rhythm correlated with ethylene production. ACC levels in both cultivars show fluctuations corresponding to the ethylene rhythm previously observed. It appears that at least two separate mechanisms may be involved in generating high-amplitude ethylene rhythms in sorghum, one in response to the loss of phytochrome B function and another in response to shading.

Paraneoplastic pemphigus associated with follicular dendritic cell sarcoma arising from Castleman's tumor

Paraneoplastic pemphigus (PNP) is associated with various forms of underlying neoplasia. We report a patient with PNP associated with an intraabdominal follicular dendritic cell sarcoma that developed from a Castleman's tumor that had preexisted for 40 years.

Complement-fixing abilities and IgG subclasses of autoantibodies in epidermolysis bullosa acquisita

Epidermolysis bullosa acquisita (EBA) is an autoimmune-mediated subepidermal bullous disease in which the target of the autoantibodies is type VII collagen, a major component of anchoring fibrils. The purpose of this study was to evaluate the complement-fixing abilities and IgG subclass distribution of autoantibodies in EBA, and to also attempt to investigate the relation between inflammation, complement fixation and IgG subclass distribution in EBA patients. Only 2 sera of 18 patients (11%) showed weak complement-fixing abilities. IgG1 and IgG4 were the most frequently and intensely stained IgG subclasses in EBA sera. We could not find any relationship between the clinico-pathologic types, complement-fixing abilities and IgG subclasses in EBA. These results suggested that complement activation may not be a key factor of bulla formation in EBA.

Localized mucosal involvement and severe pulmonary involvement in a young patient with paraneoplastic pemphigus associated with Castleman's tumour

We describe a 19-year-old female patient who developed recurrent ulcerations limited to the orogenital mucosa for the last 3 years. She also developed dyspnoea 5 months after the onset of the orogenital lesions. Castleman's tumour of the retroperitoneum was found incidentally during routine physical examination. The diagnosis of paraneoplastic pemphigus (PNP) was made by pathological and immunological studies. The orogenital ulceration responded well to corticosteroid therapy, but severe bronchiolitis obliterans progressed despite intensive care. The patient eventually died from respiratory failure. This case demonstrates the diversity of clinical features of paraneoplastic pemphigus.

Photoperiod control of gibberellin levels and flowering in sorghum

Regulation of rhythmic peaks in levels of endogenous gibberellins (GAs) by photoperiod was studied in the short-day monocot sorghum (Sorghum bicolor [L.] Moench). Comparisons were made between three maturity (Ma) genotypes: 58M (Ma1Ma1, Ma2Ma2, phyB-1phyB-1, and Ma4Ma4 [a phytochrome B null mutant]); 90M (Ma1Ma1, Ma2Ma2, phyB-2phyB-2, and Ma4Ma4); and 100M (Ma1Ma1, Ma2Ma2, PHYBPHYB, and Ma4Ma4). Plants were grown for 14 d under 10-, 14-, 16-, 18-, and 20-h photoperiods, and GA levels were assayed by gas chromatography-mass spectrometry every 3 h for 24 h. Under inductive 10-h photoperiods, the peak of GA20 and GA1 levels in 90M and 100M was shifted from midday, observed earlier with 12-h photoperiods, to an early morning peak, and flowering was hastened. In addition, the early morning peaks in levels of GA20 and GA1 in 58M under conditions allowing early flowering (10-, 12-, and 14-h photoperiods) were shifted to midday by noninductive (18- and 20-h) photoperiods, and flowering was delayed. These results are consistent with the possibility that the diurnal rhythm of GA levels plays a role in floral initiation and may be one way by which the absence of phytochrome B causes early flowering in 58M under most photoperiods.

Molecular characterization of fetal alcohol syndrome using mRNA differential display

The molecular pathogenesis of fetal alcohol syndrome (FAS) has not been well elucidated. The technique of mRNA differential display was used to characterize the etiology and to identify potential markers for FAS. Out of approximately 1,080 mRNA transcripts in mouse embryos that were analyzed, the levels of three mRNAs were altered by ethanol. Two of these mRNAs (one novel and one encoding heat shock protein 47) were also modulated by another teratogen, 3-methylcholanthrene. The third mRNA, encoding alpha-tropomyosin, was specifically up-regulated by ethanol. Consistent with the Northern blot data, immunoblot analysis demonstrated that the level of alpha-tropomyosin protein (31 kDa, most likely a brain specific isoform) was elevated in the embryos exposed to ethanol.

C2H2-171: a novel human cDNA representing a developmentally regulated POZ domain/zinc finger protein preferentially expressed in brain

We describe a novel human zinc finger cNDA. C2H2-171. This cDNA represents an mRNA which encodes a protein of 484 amino acids and a calculated molecular weight of 54 kD. Four zinc finger-like domains are found in the C-terminal end of the protein. At the N-terminus, C2H2-171 contains a POZ/tramtrack-like domain similar to that found in the tumor associated zinc finger proteins LAZ-3/BCL-6 and PLZ-F, as well as in non-zinc finger proteins. C2H2-171 RNA is preferentially expressed in the brain, and increases during the course of murine development, with maximal expression in the adult. C2H2-171 RNA is differentially expressed in brain regions, with the highest level of expression in the cerebellum. C2H2-171 RNA was expressed at high levels in primary cerebellar granule cell neurons compared to astrocytes. The gene encoding C2H2-171 is highly conserved in vertebrates, and maps to the terminus of human chromosome 1 (1q44-ter). This chromosomal location is associated with a number of cytogenetic aberrations including those involving brain developmental anomalies and tumorigenesis. These data suggest that C2H2-171 may play an important role in vertebrate brain development and function.

cDNA cloning of the 210-kDa paraneoplastic pemphigus antigen reveals that envoplakin is a component of the antigen complex

Although the 210 and 190-kDa proteins are the most frequently detected antigens reacting with sera of patients with paraneoplastic pemphigus (PNP) in immunoblot analysis, there is still uncertainty as to the nature of these PNP antigens. To isolate and characterize a cDNA clone encoding the 210-kDa PNP antigen, we screened a human keratinocyte lambda gt 11 cDNA expression library by the immunoperoxidase method with serum IgG from a PNP patient. The IgG used for the immunoscreening of a keratinocyte cDNA expression library recognized 210- and 190-kDa antigens by immunoblotting. A single clone, called here the PNP clone, producing a fusion protein that reacted strongly with the patient's IgG, was further characterized. Only the PNP patient's IgG, but not IgG from a normal control, pemphigus foliaceus, or pemphigus vulgaris patients, bound the plaques of this positive clone. Furthermore, PNP IgG affinity purified on plaques of this clone, but not unrelated clones, bound to keratinocyte cell surfaces by immunofluorescence and reacted with the 210-kDa PNP antigen by immunoblotting. EcoRI digestion of the clone's cDNA insert demonstrated a 1.4-kbp fragment. This cDNA insert was placed into a M13 mp 18 vector and sequenced. Sequence analysis revealed that the cDNA insert of the PNP clone encodes a part of the central rod domain and the COOH-terminal C domain of envoplakin, a newly defined precursor of the cornified envelope that is homologous to desmoplakin. This result demonstrates that the 210-kDa PNP antigen is envoplakin and PNP is an autoimmune disease that produces autoantibodies against intermediate filament-associated proteins in desmosomes and hemidesmosomes, desmoplakin, bullous pemphigoid antigen 1 (BPAG 1), and envoplakin.

Isolation and characterization of murine vav2, a member of the vav family of proto-oncogenes

We describe the isolation and characterization of a cDNA encoding murine vav2. vav2 shares 63% and 55% identity at the nucleic acid and amino acid levels, respectively, with vav, a proto-oncogene that plays an essential role in embryonic development and hematopoietic signal transduction. The 100 kDa Vav2 protein contains the characteristic array of structural motifs found in Vav. However, unlike vav, vav2 transcripts are widely distributed in both hematopoietic and non-hematopoietic tissues. In the adult, vav2 mRNA is found at high levels in the spleen, liver, testes and placenta. Northern blot analysis reveals two vav2 mRNA species (designated alpha and beta). The alpha species is expressed throughout development while the alpha and beta species are expressed tissue-specifically in adults. Transfection of NIH3T3 cells with expression vectors containing vav2 deletions demonstrate that elimination of 183 amino terminal residues of Vav2 is sufficient to activate its oncogenic potential. Vav2-induced transformation is characterized by the appearance of foci composed of cells in which cytokinesis and karyokinesis are uncoupled. This phenotype is comparable, but not identical, to morphological changes induced by Vav and other members of the DbI family of oncoproteins. Our results suggest that Vav family members mediate functions important in the regulation of cell architecture and proliferation in most, if not all, tissues.

Transcriptional induction of the cytochrome P4501A1 gene by a thiazolium compound, YH439

The molecular mechanism of induction of cytochromes P4501A1/2 (CYP1A1/2) by a synthetic compound YH439 was studied in rodents as well as in cultured hepatoma cells. CYP1A1-mediated ethoxyresorufin-O-deethylase activity and amounts of its immunoreactive protein were increased in a time- and concentration-dependent manner after a single dose of YH439 (150 mg/kg). Northern blot analyses revealed that YH439 rapidly increased (< or = 2 hr) the levels of CYP1A1/2 mRNAs, resulting in an increase in CYP1A protein level by > 6-fold at 8 hr after injection. After YH439 administration, the levels of CYP1A1 and CYP1A2 mRNAs peaked at 8 hr and 16 hr, respectively, before returning to control levels at 16 and 24 hr. The CYP1A protein level, on the other hand, reached a maximum at 24 hr after YH439 treatment and returned to near-control levels at 72 hr. Nuclear run-on analyses revealed that YH439 induces CYP1A1/2 gene transcription as early as 2 hr after YH439 treatment. Cytosolic electrophoretic mobility shift assays suggested that YH439 activates the CYP1A1/2 genes through the aryl hydrocarbon (Ah) receptor and the xenobiotic response elements. The dependency on the Ah receptor for the induction of CYP1A1/2 by YH439 was confirmed by the lack of CYP1A1/2 induction in the Ah receptor knock-out mice (Ahr-1-) as well as in murine hepatoma cells without a functional Ah receptor. Molecular structural analysis of YH439 and several other compounds indicated that the planarity and size of a molecule are important in its interaction with the Ah receptor and subsequent CYP1A1/2 induction. YH439 is a thiazolium compound with little aromaticity and with a two-dimensional structure different from that of the Ahs. Therefore, it represents a new class of Ah receptor ligand and CYP1A inducer.

Transcriptional inhibition of cytochrome P4502E1 by a synthetic compound, YH439

The molecular mechanism of cytochrome P4502E1 (CYP2E1) inhibition by a synthetic compound, YH439, was studied. In rats treated with YH439, N-nitrosodimethylamine demethylase activity and the amount of immunoreactive CYP2E1 were rapidly decreased in time- and dose-dependent manners. Within 2 h after a single dose of YH439 (150 mg/kg), the CYP2E1-catalyzed activity in uninduced rats was decreased by about 30% and by 43% at 24 h after YH439 injection. YH439 treatment also reduced the elevation of CYP2E1 enzyme activity in starved (induced) animals by 34%. More profound inhibition of CYP2E1 protein levels was observed by immunoblot analysis. The level of CYP2E1 catalytic activity and immunoreactive protein remained suppressed for at least 48 h and returned to normal level at 72 h after YH439 treatment. The levels of immunoreactive CYP2B1/2 protein and catalytic activity were moderately increased while little change was observed in the levels of NADPH-dependent P450 oxidoreductase activity and its protein after treatment with YH439. Unlike competitive inhibitors of CYP2E1, YH439 rapidly (within 2 h) decreased the level of CYP2E1 mRNA, while malotilate, a structural analog of YH439, slightly suppressed its level. Nuclear run-on transcription analyses at 2, 4, and 8 h post-YH439 administration revealed that the inhibition of CYP2E1 by YH439 is at the level of transcription, indicating that YH439 is a new class of CYP2E1 inhibitor. Our data demonstrate that YH439 is a powerful inhibitor of CYP2E1 expression and is thus potentially useful as a pharmacological tool to study CYP2E1 function as well as a potential therapeutic agent.

Appearance of Sézary-like atypical lymphocytes in the regressing lesions of juvenile xanthogranuloma. Its role in the spontaneous regression

A case of juvenile xanthogranuloma of the skin was sequentially biopsied for 10 months. In the electron microscopic examination of the regressing lesions, we observed that cells with highly indented nuclei, Sézary-like cells, were in close apposition to vacuolated degenerating histiocytes in many foci. In immunohistochemical stain, the number of UCHL-1+ cells were increased in regressing lesions compared with early lesions. We speculate that these Sézary-like atypical lymphocytes may be closely related to the spontaneous regression of juvenile xanthogranuloma.

Electronmicroscopic observation of the basement membrane zone in focal dermal hypoplasia

A 3-month-old boy had reticulated achromic and atrophic skin lesions on the right buttock and thigh, as well as partial syndactyly of the third and fourth toes of the right foot. With hematoxylin and eosin stain, an epidermal defect, abnormally located fat cell lobules, and absence of the upper and midportions of the dermis were observed, conforming to a typical histopathologic picture of focal dermal hypoplasia. Electron microscopic examination of the atrophic site showed loose collagen bundles, collagen fibers with loss of regular bands, abnormal fibroblasts, and disruption of the basement membrane zone. These defects in the basement membrane zone strongly suggest that abnormal formation of type IV collagen is associated with focal dermal hypoplasia, and that this abnormal formation of collagen is correlated with the clinical sign of skin atrophy.

Quantitative increases in DNA binding affinity and positional effects determine 9-cis retinoic acid induced activation of the retinoid X receptor beta homodimer

Retinoid X receptors (RXRs) exert transcriptional activities through heterodimerization with members of the nuclear hormone receptor superfamily. RXRs also act as homodimers and stimulate transcription from an RXR responsive element (RXRE) when bound to 9-cis-retinoic acid (9cRA). Here direct effects of 9cRA have been examined on biochemical and mechanistic parameters of RXR beta. It is shown that 9cRA significantly increases RXR beta homodimer binding affinity to an RXRE (Kd without ligand = 18 nM, Kd with ligand = 6 nM), while decreasing significantly the affinity of RXR beta/thyroid hormone receptor (T3R alpha) heterodimer binding to the same element. Effects on other response elements are also examined. The RXR beta homodimer was found to contact both halves of the RXRE direct repeat, irrespective of the effect of added ligand, while the RXR beta/T3R alpha heterodimer contacted the element only through a specific half-site. Binding of the homodimer to the element functionally activates RXR beta, since RXR beta enhanced transcription in vitro from a specific template in a ligand-dependent fashion. In agreement, transfection of RXR beta alone (but not RXR beta/T3R alpha) led to ligand-dependent activation of a reporter containing the RXRE. Taken together, 9cRA facilitates functional activation of the RXR beta homodimer in an element-dependent manner.

Different pharmacological characteristics of structurally similar benzylisoquinoline analogs, papaverine, higenamine, and GS 389, on isolated rat aorta and heart

In the present study, we compared the pharmacological properties of structurally similar benzylisoquinoline compounds, papaverine, higenamine, and GS 389, using isolated rat aorta and atrial preparations. The three benzylisoquinoline compounds, concentration dependently, relaxed phenylephrine (3 microM) induced contraction of rat aortic rings, with the rank order of potency being higenamine > papaverine > GS 389. They also relaxed high K+ (60 mM) induced contraction, with the rank order of potency being papaverine > GS 389 >> higenamine. The relaxation was not modified by the presence of endothelium. To assess whether these compounds directly interfere with Ca2+ influx, the effects of these compounds on Ca(2+)-induced contraction in Ca(2+)-free media were examined. Among the three compounds, papaverine most strongly inhibited Ca(2+)-induced contraction of both K+ stimulated and phenylephrine-stimulated aorta. Higenamine was least potent in inhibition of Ca(2+)-induced contraction in high K+ depolarized aorta. In atrial tissues, lower concentrations of papaverine increased spontaneous beats and isometric tension, whereas above 30 microM its action was reversed. GS 389 decreased heart rate without affecting the contractility. On the other hand, higenamine concentration dependently increased both heart rate and isometric tension, as well as cyclic AMP levels in atrial tissues as a result of beta-receptor activation. Cyclic AMP and cyclic GMP dependent phosphodiesterases from rat atrial and ventricular tissue homogenates were inhibited by papaverine and GS 389, but not by higenamine. These results suggest that calcium antagonistic action of these compounds is at least in part responsible for vasodilation action, but not for cardiac action.(ABSTRACT TRUNCATED AT 250 WORDS)

Recombinant thyroid hormone receptor and retinoid X receptor stimulate ligand-dependent transcription in vitro

The thyroid hormone and retinoid X receptors form a heterodimer with each other and mediate thyroid hormone (T3)-dependent transcription. Retinoid X receptor, in addition, forms a homodimer and mediates 9-cis-retinoic acid-dependent transcription. Here, recombinant thyroid hormone receptor and recombinant retinoid X receptor beta expressed from baculovirus vectors have been studied for ligand-mediated activation of transcription in vitro. We show that the two recombinant receptors, most likely as a heterodimer, cooperatively enhance transcription in vitro from a template containing functional T3 responsive elements. The enhancement was specific for the T3 responsive element and was greatest when T3 was added to the reaction (approximately 14-fold increase). Albeit to a lesser degree, the two receptors also directed transcription in the absence of T3. Template competition experiments suggest that the two receptors enhance formation of the preinitiation complex and that activation by T3 occurs when the ligand binds the receptor prior to (or during), but not after, the formation of the preinitiation complex. Although 9-cis-retinoic acid had no effect on the T3-dependent transcription, this ligand activated transcription in vitro directed by recombinant retinoic X receptor beta, most likely as a homodimer. This activation was observed when using nuclear extracts from embryonal carcinoma cells as a source of basal transcription factors, but not those from B lymphocytes. These results demonstrate that transcriptional activation mediated by T3 and 9-cis-retinoic acid can be reconstituted in vitro with the respective recombinant receptors.

Hypertrichosis universalis congenita: a separate entity, or the same disease as gingival fibromatosis?

Hypertrichosis universalis congenita is an extremely rare disorder characterized by generalized hypertrichosis. It is generally accepted as being inherited as an autosomal dominant trait with varying expression. Many aspects of this disease are still unknown. Several reports associating hypertrichosis and gingival fibromatosis raise the question of whether they are separate entities or the same disease with different expressions of the underlying process. Hypertrichosis universalis congenita occurred in a 6-year-old girl without known family history. Her facial features were simian-like and her gingiva was moderately hyperplastic. We pose the question of whether or not these phenomena are related.

NO- and NO2-carrying molecules potentiate photorelaxation in rat trachea and aorta

Photorelaxation elicited by ultraviolet light (366 nm) was investigated on isolated rat thoracic aorta and trachealis. Rat tracheal smooth muscle but not aorta did not show UV-induced photorelaxation. Both streptozotocin, NO-carrying molecule and N omega-nitro-L-arginine, NO2-carrying molecule significantly enhanced photorelaxation, concentration-dependently, in rat trachealis and aorta. Methylene blue (10 microM) inhibited the potentiation action of streptozotocin and N omega-nitro-L-arginine in both tissues. Superoxide dismutase (300 U/ml) enhanced streptozotocin- and N omega-nitro-L-arginine-potentiated photorelaxation in rat trachealis, while pyrogallol (0.1 mM), a potent O2- generating agent, inhibited streptozotocin-potentiated photorelaxation in trachealis. Streptozotocin was much more effective than N omega-nitro-L-Arginine in potentiating of photorelaxation elicited by UV light in both tissues. From these findings, we conclude that streptozotocin and N omega-nitro-L-arginine produce EDRF like labile substance(s) by UV irradiation.

Endothelial potentiation of relaxation response to ascorbic acid in rat and guinea pig thoracic aorta

The role of the endothelium was evaluated in the relaxation of rat and guinea pig aortic rings induced by ascorbic acid. Ascorbic acid relaxed rat and guinea pig aortic rings that were previously contracted with submaximal dose of phenylephrine (PE), in a concentration dependent manner. Removal of the endothelium significantly reduced the sensitivity but not the magnitude of the response to ascorbic acid. Methylene blue, but not propranolol, blocked the endothelial augmentation of vascular relaxation to ascorbic acid. Vessels precontracted with potassium chloride (high K+) were also relaxed by ascorbic acid. Methylene blue also inhibited the response to ascorbic acid in the intact vessels precontracted with high K+. A23187 and acetylcholine, but not ADP, variably caused endothelium dependent component relaxation in guinea pigs, whereas all of these three probes constantly caused it. In Ca(2+)-free medium, Ca(2+)-induced contraction of high K(+)-depolarized rat aorta was inhibited by the presence of ascorbate, which was more pronounced in endothelium intact rings than in endothelium denuded ones. PE-induced contraction in the presence of different concentrations of ascorbate reduced both the sensitivity and the maximal contractile force in rat aorta. Ascorbic acid (0.125-32 mM) did not change the pH in the medium. From these findings, it is speculated that 1) receptor- and potential-operated Ca2+ channels may be modulated by ascorbate, 2) endothelium has a significant role in promoting relaxation induced by ascorbic acid.

Human fetal heart development after mid-term: morphometry and ultrastructural study

A total of 44 normally developed human fetal hearts aged from 17 to 40 weeks gestation were provided for routine ultrastructural and morphometric studies. For morphometric analysis, the maximal thicknesses of the anterior, lateral and posterior wall of both ventricles and that of interventricular septum were measured and the left-to-right thickness ratios calculated. The cross-sectional areas of both ventricles in the plane of the greatest heart diameter were measured with computerized image analysis system. Data were analyzed using linear regression and one-way analysis of variance. Myofibril formation occurred by attachment of thin filaments into amorphous Z materials which were presented in sarcolemmal plaques, sarcoplasmic condensations, desmosomes and in Z lines. From these Z centers, myofibrils radiated many directions and branched and anastomosed with further development. This pattern of myofibrillar development continued throughout the whole fetal period. A transverse tubule system was clearly evident in later fetal development. It occurred by invagination of sarcolemma into myocardial cells and formation of subsarcolemmal caveolae. Mitochondria, well-developed Golgi complexes, glycogen granules and well-developed microvessels were found throughout the whole fetal period. Binucleated myocytes appeared by 32 weeks gestation and this suggests that myocyte hyperplasia may cease before birth in humans. The growth of both ventricular walls, the interventricular septum and that of both ventricular cross-sectional areas showed linear regression, and the left-to-right wall thickness ratios were nearly constant. Also, there were no differences in morphometric data between the left and right ventricles. In conclusion, development of the myocyte is an ongoing process which may be continued in the post-natal period in humans, and our statistical results do not support the theory of the right ventricular dominance during the fetal period.

Two upstream elements activate transcription of a major histocompatibility complex class I gene in vitro

Expression of major histocompatibility complex (MHC) class I genes exhibits unique tissue and developmental specificity. In an effort to study molecular mechanisms of MHC class I gene regulation, an in vitro transcription system has been established. In B cell nuclear extracts a template DNA containing the mouse H-2Ld promoter sequence accurately directed RNA polymerase II-dependent transcription of a G-free cassette. A conserved class I regulatory complex previously shown to moderately enhance promoter activity in vivo enhanced transcription in vitro by 2-3 fold. Much of this enhancement was accounted for by a 40 bp fragment within the complex, which was capable of activating a basal H-2Ld promoter in either orientation. Farther downstream, another element called site B was identified, which independently activated MHC class I transcription in vitro by 2-4 fold. Site B bound a specific nuclear factor(s) through an NF-1 binding site but not through a neighboring CCAAT site. The functional significance of site B in vivo was demonstrated in transfection experiments in which site B enhanced MHC class I promoter activity to a degree comparable to that seen in vitro. With the identification of the two upstream activators, MHC class I genes may serve as a model to study roles of sequence-specific DNA-binding proteins in transcription in vitro.