Analysis of the myogenin promoter reveals an indirect pathway for positive autoregulation mediated by the muscle-specific enhancer factor MEF-2

Transcriptional cascades that specify cell fate have been well described in invertebrates. In mammalian development, however, gene hierarchies involved in determination of cell lineage are not understood. With the recent cloning of the MyoD family of myogenic regulatory factors, a model system has become available with which to study the dynamics of muscle determination in mammalian development. Myogenin, along with other members of the MyoD gene family, possesses the apparent ability to redirect nonmuscle cells into the myogenic lineage. This ability appears to be due to the direct activation of an array of subordinate or downstream genes which are responsible for formation and function of the muscle contractile apparatus. Myogenin-directed transcription has been shown to occur through interaction with a DNA consensus sequence known as an E box (CANNTG) present in the control regions of numerous downstream genes. In addition to activating the transcription of subordinate genes, members of the MyoD family positively regulate their own expression and cross-activate one another's expression. These autoregulatory interactions have been suggested as a mechanism for induction and maintenance of the myogenic phenotype, but the molecular details of the autoregulatory circuits are undefined. Here we show that the myogenin promoter contains a binding site for the myocyte-specific enhancer-binding factor, MEF-2, which can function as an intermediary of myogenin autoactivation. Since MEF-2 can be induced by myogenin, these results suggest that myogenin and MEF-2 participate in a transcriptional cascade in which MEF-2, once induced by myogenin, acts to amplify and maintain the myogenic phenotype by acting as a positive regulator of myogenin expression.

Exposure to residential electric and magnetic fields and risk of childhood leukemia

The relation between exposure to electric and magnetic fields in the home, as assessed by measurements, wiring configuration, and self-reported appliance use, and risk of leukemia was investigated in a case-control study among children from birth to age 10 years in Los Angeles County, California. Cases were ascertained through a population-based tumor registry from 1980 to 1987. Controls were drawn from friends and by random digit dialing. Interviews were obtained from 232 cases and 232 controls. Available for analysis were measurements of the magnetic field in the child's bedroom over 24 hours or longer (164 cases and 144 controls), spot measurements of magnetic and electric fields (140 cases and 109 controls), and wiring configuration (219 cases and 207 controls). No clear associations between leukemia risk and measured magnetic or electric fields were seen. An association between the Denver Wertheimer-Leeper wiring configuration and childhood leukemia risk was observed (odds ratio for very high relative to very low current and underground configuration combined = 2.15, 95% confidence interval 1.08-4.28; p for trend = 0.008) and was not substantially altered by adjustment for potential confounding factors. Cases were more likely than controls to report use of several appliances that produce high electric and magnetic fields. Our results support an association between childhood leukemia risk and wiring configuration, but not direct measurements of electric and magnetic fields.

Molecular control of myogenesis: antagonism between growth and differentiation

Insight into the molecular mechanisms that control establishment of the skeletal muscle phenotype has recently been obtained through cloning of a family of muscle-specific regulatory factors that can activate myogenesis when transfected into non-muscle cells. This family of factors, which includes MyoD, myogenin, myf-5, and MRF4, can bind DNA and transactivate muscle-specific genes in collaboration with ubiquitous cellular factors. Growth factors play an antagonistic role in myogenesis by suppressing the actions of the myogenic regulatory factor family. This review will focus on the regulation and mechanism of action of this family of myogenic regulatory factors and on the central role of peptide growth factors in modulating their expression and biological activities.

Stomach and duodenal alcohol and aldehyde dehydrogenase isozymes in Chinese

Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) isozyme phenotypes were determined in surgical and endoscopic biopsies of the stomach and duodenum by agarose isoelectric focusing. gamma-ADH was found to be the predominant form in the mucosal layer whereas beta-ADH was predominant in the muscular layer. Low-Km ALDH1 and ALDH2 were found in the stomach and duodenum. High-Km ALDH3 isozymes occurred only in the stomach but not in the duodenum. The isozyme patterns of gastric mucosal ALDH2 and ALDH3 remained unchanged in the fundus, corpus, and antrum. The stomach ALDH3 isozymes exhibited a Km value for acetaldehyde of 75 mM, and an optimum for acetaldehyde oxidation at pH 8.5. Since the Km value was high, ALDH3 contributed very little, if any, to gastric ethanol metabolism. The activities of ALDH in the gastric mucosa deficient in ALDH2 were 60-70% of that of the ALDH2-active phenotypes. These results indicate that Chinese lacking ALDH2 activity may have a lower acetaldehyde oxidation rate in the stomach during alcohol consumption.

Isolation of high-Km aldehyde dehydrogenase isoenzymes from human gastric mucosa

Human stomach aldehyde dehydrogenase-3 isoenzymes were isolated by DEAE-cellulose, CM-Sephadex, and 5' AMP-Sepharose chromatographies to apparent homogeneity. The subunit of the isoenzymes was determined to be 55,000 daltons by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The kinetic constants for oxidation of various aliphatic and aromatic aldehydes were determined. The Km value for straight-chain aldehydes decreased over 9,000 fold when chain length increased from C2 to C7. The Vmax/Km value for heptaldehyde was 10-fold higher than that for benzaldehyde. NAD+ was a much better cosubstrate than NADP+. The human stomach aldehyde dehydrogenase-3 isoenzymes were insensitive to disulfiram inhibition and were not activated or inhibited by magnesium ions.

High energy laser irradiation and electric surgery for obstructive gastrointestinal cancer

A total of 35 patients with advanced obstructive gastrointestinal cancer received monopolar electrosurgery and Nd: YAG laser therapy from January 1985 to June 1988. These included 13 cases of esophageal cancer (U/3 6, M/3 2, L/3 5), 14 case of gastric cancer (cardia 7, corpus 3, antrum 4), and 8 cases of rectal cancer. Twenty (esophageal 9, stomach 8, rectal 3) of 35 patients had much improved results, with the size of the lesion reduced over 90%, and the endoscope could smoothly pass through the stenotic area after electrosurgery or laser therapy. The other 12 patients had partially improved results with the tumor size being reduced 50-90% and the patients could take semiliquid food easily. Both groups of much improved or partial improved had a statistically significant difference (P less than 0.01) compared to the group of failures to treatment. Two patients developed bleeding after treatment. Twenty-one patients died of causes other than complications of electrosurgery or laser therapy. The average survival was 6.8 months. Nd: YAG laser and electrosurgery can provide good palliative results and contribute to a good quality of life in advanced obstructive gastrointestinal cancer.

Ultrastructural evidence for the destruction of Schistosoma mansoni sporocysts associated with elevated lysosomal enzyme levels in Biomphalaria glabrata

The activity levels of serum acid phosphtase, aminopeptidase, and lysozyme in a Brazilian strain of Biomphalaria glabrata were ascertained at 1, 2, and 3 hr after mechanical wounding or injection with albumin on the 30th day postexposure to a compatible strain of Schistosoma mansoni miracidia and found to be elevated. Parallel transmission electron microscope studies on daughter sporocysts and developing cercariae at these time intervals revealed progressive disintegration of the parasites that was associated with increased numbers of host granulocytes abutting the sporocyst surfaces. Furthermore, host granulocytes were observed to have passed through eroded sporocyst walls and attacked developing cercarial embryos. It is proposed that the elevated levels of lysosomal hydrolases released from activated host granulocytes as a result of challenge altered the parasite's surfaces so that these were recognized as nonself. Consequently, additional host granulocytic response, which included additional release of lysosomal enzymes into serum as well as phagocytosis of remnants of both sporocysts and developing cercariae, was elicited.

Dosimetry of high dose rate intracavitary radiation therapy using Co-60 and Ir-192 sources

For decades, the high dose rate sources of Co-60 and Ir-192 have been used in remote controlled afterloading brachytherapy. A small volume ion chamber was used to measure the dose rate in varying distances from the sources. The entire dose distribution around the source was tabulated and the data were used to calculate the treatment time for individualized patient setting. A solid diode detector was used to plot the relative distance dose and the symmetrical dose distribution of the sources. Thermoluminescence dosimetry (TLD) was used for spot-checking of the dose. The dose distribution in the clinically useful range of 2-5 cm was carefully estimated. When normalized at 2.0 cm from the source, the dose rate at 5.0 cm was 17.1% for the Co-60 source and 18.4% for the Ir-192 source. It is clearly demonstrated that Ir-192 offers no dosimetric advantages, which is contrary to what used to be believed by some clinicians. The parameters of the computer treatment planning system have to be corrected and then adopted into clinical application.

A clinical controlled trial of endoscopic sclerotherapy for repeated esophageal variceal bleeding

Thirty-seven patients with postnecrotic cirrhosis of the liver and 13 patients with primary hepatoma were proven to have repeated bleeding from ruptured esophageal varices. Clinically controlled trials were performed by assigning patients to either sclerotherapy or control arms (25 patients each). Combined intra-variceal and para-variceal injection before an upper endoscopic examination was performed in the sclerotherapy group. In all 25 sclerotherapy cases (100%) hemostasis was successful, which was a statistically significant success rate compared to the control group (52.0%) (p less than 0.01). In the sclerotherapy group 20% (5/25 cases) developed rebleeding, which was less than the 48.0% (7 cases of continuous bleeding and 5 cases of rebleeding) of the control group (p less than 0.05). Four cases (16.0%) in the sclerotherapy group died of erosive gastritis with massive bleeding, compared to 8 fatalities (32.0%) in the control group, because of uncontrolled esophageal variceal bleeding. Endoscopic sclerotherapy is a very effective method for arresting bleeding esophageal varices, and for decreasing the rebleeding rate.

Diaphragmatic defect as a cause of massive hydrothorax in cirrhosis of liver

A 56-year-old woman with a 2-year history of cirrhosis of the liver and frequent right pleural effusion was admitted with intractable shortness of breath. Chest x-ray examination showed marked pleural effusion of the right lung field with a shift of the mediastinum to the left. Ascites was not conspicuous. Except for the liver cirrhosis, there was no clinical evidence of other underlying diseases. The patient died with a relatively short course after hospitalization. At autopsy, an apparent bleb with 1-mm hole in the tendinous portion of the right diaphragm was noted. We suggest that the ascitic fluid directly crossed the diaphragmatic defect to the pleural cavity, which contributed to the hydrothorax. In this article we review the pertinent literature.

Hepatitis B virus-associated membranous glomerulonephropathy

A variety of extrahepatic abnormalities have been described in patients with hepatitis B viral infection, including the prodromal arthritis (serum sickness-like) syndrome, polyarteritis nodosa, and glomerulonephropathy. Five patients with hepatitis B virus (HBV)-associated membranous glomerulonephropathy (MGN) were persistent carriers of HBsAg. The deposition of HBsAg in the renal lesions of these patients was proved by using monospecific antibody and immunofluorescence technique. These findings support the hypothesis of an etiological correlation of hepatitis B viral infection with some cases of MGN. HBV-associated MGN may be much more frequent in the world than previously reported, and more cases must be collected for the understanding of this unique entity.

Human stomach alcohol and aldehyde dehydrogenases (ALDH): a genetic model proposed for ALDH III isozymes

Isozyme phenotypes of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) from human gastroendoscopic as well as surgical gastric biopsies were determined by starch gel electrophoresis and agarose isoelectric focusing. gamma gamma ADH isozymes were expressed predominantly in the mucosal layer of the stomach, whereas beta beta isozymes were in the muscular layer. In the 56 gastroendoscopic mucosal biopsies examined, the homozygous ADH3 1-1 phenotype was found in 75% of the samples, and the heterozygous ADH3 2-1 phenotype in 25%. Accordingly, the gene frequencies of the alleles ADH1/3 and ADH2/3 were calculated to be 0.88 and 0.12, respectively. Using a modified agarose isoelectric focusing procedure, gastric ALDH I, ALDH II, and up to five ALDH III forms could be clearly resolved. The ALDH III isozymes accounted for more than 80% of the total ALDH activities in gastric mucosa and exhibited Km values in the millimolar range for propionaldehyde at pH 9.0. Forty-five percent of the 55 gastroendoscopic biopsies studied lacked ALDH I isozyme. The complex gastric ALDH III isozyme phenotypes seen in these biopsies fall into three patterns. They can be interpreted by a genetic hypothesis, based on a dimeric molecule, in which there are two separate genes, ALDH3a and ALDH3b, with the ALDH3b locus exhibiting polymorphism. The homozygous phenotypes ALDH3b 1-1 and ALDH3b 2-2 were found to be 4 and 76%, respectively, and the heterozygous ALDH3b 2-1 phenotype 20%, of the total. Therefore, the allele frequencies for ALDH1/3b and ALDH2/3b were calculated to be 0.14 and 0.86, respectively. Several lines of biochemical evidence consistent with this genetic model are discussed.

A case study of hospital operations management

This paper discusses a study to investigate various operations management problems in a newly opened, modern regional hospital in Hong Kong. The findings of the study reveal that there exist in the hospital a number of current and potential problem areas. Recommendations for solving these problems are suggested with a view to improving the overall operational efficiency and effectiveness of the hospital.