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Biomedical subjects

H M Chung

Publications and source records attributed to H M Chung.

84 records · Page 5Linked to original sources
PubMed1978

Developmental studies on an apparent cell-lethal mutant gene-ut-in the Mexican axolotl, Ambystoma mexicanum.

The discovery of a new mutant gene in stocks of the Mexican axolotl derived from breeding stock of the Hubrecht Laboratory, the Netherlands, is described. The gene appears to be a simple recessive and displays complete penetrance. ut/ut larvae develop normally through hatching, but begin to lag in growth and display characteristics defects in gill and limb formation shortly thereafter. The results of parabiosis of normal and mutant embryos, as well as embryological transplants of mutant limb and branchial rudiments, support the conclusion that the gene ut is expressed as an 'autonomous-cell lethal'. Despite gross morphological defects in ut/ut larvae, comparisons between normal and mutant animals of the protein spectra of various tissues and organs revealed no substantial differences. A subtle change in the metabolism of ut/ut larvae apparently, therefore, leads to developmental arrest.

Ambystoma↗
PubMed1978

Home treatment of uremia with gastrointestinal dialysis.

Twenty patients with end-stage renal disease and a creatinine clearance of less than 5 ml/min were tre ated with oral gastrointestinal (GI) dialysis. The dialyzate contained an electrolyte solution with 180-220mmoles/l of mannitol. In fasting state in the morning the self-prepared 7 liters of dialyzate was drunk at a rate of one glass every 5 minutes for about 3 hours. Intermittent diarrhea with passage of watery fluid occurred during the whole period. After each treatment the average drop in BUN in individual patients was 11--22%, but no significant decrease in serum creatinine. With twice to thrice weekly GI dialysis uremic symptoms such as anorexia, nauseal and vomiting were usually improved with slight prolongation of life. However, treatment is usually difficult when the patient becomes oliguric or anuric, so its value in long-term management of chronic uremia is limited. Most of our patients either died or shifted to hemodialysis within a few months of institution of the therapy.

Adult↗
PubMed1977

Genetic and experimental studies on three associated mutant genes in the Mexican axolotl: st (for stasis), mi (for microphthalmic) and h (for hand lethal).

Three mutant genes, st, mi, and h, were discovered in an axolotl male received from Mexico City. All three are recessive to their normal alleles, and appear to segregate independently. Larvae homozygous for st (for stasis) suffer blockage of the circulation at hatching or shortly after, and the majority soon die; any surviving live only a few weeks at most. The mi/mi (microphthalmic) can be identified at the feeding stage. None survives more than a few days. The h/h (hand lethals) live until the digits have appeared on the forelimb. They may then be recognized by the thumb-like orientation of digit 1. Transplants from st/st embryos into normal produce normal structures which persist indefinitely. Those from mi/mi and h/h donors do not survive. The structures (forelimb, gills) derived from h/h donors grow for a relatively long time, and their final death and degeneration result in defects leading to death of most of the recipients. Parabiosis is of no benefit to st/st or h/h mutants and leads to the death of the normal twin; mi/mi mutants undergo a gradual absorption by the normal twin.

Ambystoma↗
PubMed1975

Experimental studies on a lethal gene (1) in the Mexican axolotl, Ambystoma mexicanum.

1. Gene ł is a recessive lethal factor found in the white strain of axolotls. Animals heterozygous for the gene are phenotypically normal. When mated with each other they give offspring 25% of which exhibit the lethal effects of the gene. 2. The ł/ł homozygotes develop normally to an advanced embryonic stage (Harrison stage 40) before the effects of the gene are first manifested. They then come to display a characteristic combination of abnormalities, including a disproportionately small head, small and poorly developed eyes, abnormal poorly developed gills, undifferentiated limb buds, and reduced overall growth rate. They may feed briefly, but soon stop and invariably die within a few weeks of the time of hatching. 3. The action of gene ł has been analyzed by parabiosing mutant and normal embryos, and by grafting various organ primordia reciprocally between mutant and normal embryos. Parabiosis to normal embryos fails to correct the abnormalities of the mutants, although their survival may be somewhat prolonged. Grafts of mutant organ primordia (eye, limb, gill, pronephros, gonad, head) also invariably fail to show improved development or to survive on normal hosts; normal organ primordia develop normally on mutant hosts so long as the mutant survives. These experiments indicate that gene ł is a recessive autonomous cell lethal affecting all of the organ systems during late embryonic and early larval development.

Ambystoma↗
PubMed1975

Association of an ultraviolet irradiation sensitive cytoplasmic localization with the future dorsal side of the amphibian egg.

Drastic alterations in neural morphogenesis can be induced by ultraviolet irradiation of the amphibian egg. The target area of U.V. was determined either by direct irradiation of various regions of the egg or by comparing the area of the U.V. hit with the location of the dorsal lip. Axolotl eggs which displayed easily recognizable gray crescents were employed for the direct irradiation experiments and albino axolotl eggs were used for a comparison of the U.V. sensitivity of the animal and vegetal halves of the egg. Marked frog eggs were employed to determine the relationship between the sensitive area and the site of formation of the dorsal lip. It was concluded that the dorsal marginal zone of the fertilized, uncleaved egg was the most sensitive area of the egg. Ovarian homogenates provide a source of material for correcting, by microinjection, the effects of U.V.

Ambystoma↗
PubMed1975

Repair of ultraviolet irradiation damage to a cytoplasmic component required for neural induction in the amphibian egg.

Localized ultraviolet irradiation of the amphibian egg destroys a cytoplasmic component that is required for neural induction. Destruction of that component severely diminishes the inducing capacity of the dorsal lip at gastrulation, as determined by embryological assays. Repair of the ultraviolet lesion can be achieved by replacing the dorsal lip of the irradiated embyro with a lip from an unirradiated embryo.

Animals↗
PubMedDate not supplied

Sodium excretion in advanced cirrhosis: effect of expansion of central blood volume and suppression of plasma aldosterone.

Sodium excretion in 13 patients with decompensated cirrhosis was measured under baseline conditions of water loading (n = 13) and during conditions designed to improve effective blood volume including: head-out water immersion alone (n = 13); norepinephrine infusion alone (n = 6), and combined norepinephrine and head-out water immersion (n = 6). All 13 patients were in positive sodium balance under baseline conditions, with a mean plasma aldosterone concentration of 78.7 +/- 15.6 ng per dl. In only four patients was plasma aldosterone less than 50 ng per dl. During head-out water immersion alone, 5 patients achieved negative sodium balance and, in all 5, plasma aldosterone was less than 50 ng per dl (mean = 23.0 +/- 5.3 ng per dl). However, the mean plasma aldosterone during head-out water immersion in the eight patients who remained in positive sodium balance during this maneuver was 64.0 +/- 11.9 ng per dl (p less than 0.01). During norepinephrine alone, positive sodium balance was maintained in all patients, and plasma aldosterone was not significantly different from baseline. Combining norepinephrine and head-out water immersion resulted in the largest and most consistent negative sodium balance. The mean plasma aldosterone concentration was decreased significantly (78.7 +/- 15.6 to 32.6 +/- 9.9 ng per dl (p less than 0.05). Regardless of the maneuver performed, no patient in whom aldosterone exceeded 50 ng per dl achieved negative sodium balance. Furthermore, only in those studies utilizing head-out water immersion, with or without norepinephrine, was negative sodium balance seen.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldosterone↗
PubMedDate not supplied

Spatial expression of a DNA repair gene, N-methylpurine-DNA glycosylase (MPG) during development in mice.

BACKGROUND: DNA repair is a crucial phenomenon that maintains the chromosome integrity of genome which are continuously damaged by endogenous and exogenous alkylating agents. If the damaged DNA is not repaired, it may lead to mutation, chromosomal aberration, aging and cancer. N-methylpurine-DNA glycosylase (MPG), a ubiquitous DNA repair enzyme, removes N-methylpurine and other damaged purines in DNA. MATERIALS AND METHODS: MPG mRNA expression was revealed at various stages of mouse development from day 7.5 p.c. (post coitum) embryo to day 400 mature adult by Northern blot hybridization or RT-PCR. RESULTS: MPG transcripts were abundant in the mouse embryo during pregnancy and in adult testis and ovary. The MPG mRNA level in the testis was low in 1-week-old mice, but the level showed its maximum among the organs tested in 4-week-old young adults. In placenta, the level of MPG mRNA continuously decreased from day 7.5 p.c. to day 17.5 p.c. CONCLUSIONS: The spatial expression of MPG gene is highly regulated. Transcription of MPG is maximum in rapidly dividing and growing tissues during development. These data suggest that an elevated rate of MPG transcription is required for DNA replication.

Animals↗
PubMedDate not supplied

[The detection of cyanobacterial cells by a non-fluorescent in situ hybridization method].

Seven cyanobacterial strains (Anabaena macrospora NIER10016, Oscillatoria sp. NIER10042, Microcystis aeruginosa NIER10015, M. ichtyoblabe NIER10025 and NIER10040, M. novacekii NIER10029, and M. wesenbergii NIER10068) were tested by a non-fluorescent in situ hybridization method using two specific horseradish peroxidase--labeled oligonucleotide probes and two chromogenic substrates. This approach was shown to be appropriate for analysis of natural samples.

Cyanobacteria↗