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Biomedical subjects

H W Huang

Publications and source records attributed to H W Huang.

At least 19 recordsLinked to original sources
PubMed2001

Lactate dehydrogenase genes of caiman and Chinese soft-shelled turtle, with emphasis on the molecular phylogenetics and evolution of reptiles.

L-Lactate dehydrogenase (LDH) cDNAs encoding for LDH-A(4) (muscle) and LDH-B(4) (heart) isozymes from caiman (Caiman crocodilus apaporiensis) belonging to the order Crocodilia and Chinese soft-shelled turtle (Pelodiscus sinensis) belonging to the order Chelonia were sequenced. The phylogenetic relationships of the newly determined cDNA and their deduced protein sequences, as well as the previously published sequences of vertebrate LDH isozymes, were analyzed by various phylogenetic tree construction methods. These results indicated that Chelonia is indeed more closely related to Crocodilia. The divergent times between caiman and alligator, turtle and soft-shelled turtle, and Chelonia and Crocodilia were estimated to be approximately 36, 100 and 177 million years, respectively.

Alligators and Crocodiles↗
PubMed2001

Site-directed mutation of the highly conserved region near the Q-loop of the cytochrome bd quinol oxidase from Escherichia coli specifically perturbs heme b595.

Cytochrome bd is one of the two quinol oxidases in the respiratory chain of Escherichia coli. The enzyme contains three heme prosthetic groups. The dioxygen binding site is heme d, which is thought to be part of the heme-heme binuclear center along with heme b(595), which is a high-spin heme whose function is not known. Protein sequence alignments [Osborne, J. P., and Gennis, R. B. (1999) Biochim. Biophys Acta 1410, 32--50] of cytochrome bd quinol oxidase sequences from different microorganisms have revealed a highly conserved sequence (GWXXXEXGRQPW; bold letters indicate strictly conserved residues) predicted to be on the periplasmic side of the membrane between transmembrane helices 8 and 9 in subunit I. The functional importance of this region is investigated in the current work by site-directed mutagenesis. Several mutations in this region (W441A, E445A/Q, R448A, Q449A, and W451A) resulted in a catalytically inactive enzyme with abnormal UV--vis spectra. E445A was selected for detailed analysis because of the absence of the absorption bands from heme b(595). Detailed spectroscopic and chemical analyses, indeed, show that one of the three heme prosthetic groups in the enzyme, heme b(595), is specifically perturbed and mostly missing from this mutant. Surprisingly, heme d, while known to interact with heme b(595), appears relatively unperturbed, whereas the low-spin heme b(558) shows some modification. This is the first report of a mutation that specifically affects the binding site of heme b(595).

Alanine↗
PubMed2001

Collective dynamics in fully hydrated phospholipid bilayers studied by inelastic x-ray scattering.

The short wavelength density fluctuation of DLPC (dilaurylphosphatidylcholine) bilayers close to full hydration has been studied by the inelastic x-ray scattering technique below and above the main transition temperature. The analysis based on a generalized three effective eigenmode theory allows us to construct the dispersion relation of the high frequency sound mode for the first time. The marked softening of the excitation near k = 14 nm(-1), corresponding to the lipid chain-chain correlation peak in the structure factor, in the L(alpha) phase implies prevalent occurrences of short-wavelength in-plane motions of lipid chains that might be of importance for transportation of small molecules across membranes.

Lipid Bilayers↗
PubMed2001

Barrel-stave model or toroidal model? A case study on melittin pores.

Transmembrane pores induced by amphiphilic peptides, including melittin, are often modeled with the barrel-stave model after the alamethicin pore. We examine this assumption on melittin by using two methods, oriented circular dichroism (OCD) for detecting the orientation of melittin helix and neutron scattering for detecting transmembrane pores. OCD spectra of melittin were systematically measured. Melittin can orient either perpendicularly or parallel to a lipid bilayer, depending on the physical condition and the composition of the bilayer. Transmembrane pores were detected when the helices oriented perpendicularly to the plane of the bilayers, not when the helices oriented parallel to the bilayers. The evidence that led to the barrel-stave model for alamethicin and that to the toroidal model for magainin were reviewed. The properties of melittin pores are closely similar to that of magainin but unlike that of alamethicin. We conclude that, among naturally produced peptides that we have investigated, only alamethicin conforms to the barrel-stave model. Other peptides, including magainins, melittin and protegrins, all appear to induce transmembrane pores that conform to the toroidal model in which the lipid monolayer bends continuously through the pore so that the water core is lined by both the peptides and the lipid headgroups.

Animals↗
PubMed2001

Hematometra of the rudimentary horn of a unicornuate uterus resulting from cesarean section.

A 30-year-old woman complained of increasing dysmenorrhea and progressive right lower-quadrant pain after cesarean section. A pelvic mass was observed and subsequently a congenital müllerian anomaly was diagnosed upon serial examination. We report the first apparent case of hematometra of the rudimentary horn of a unicornuate uterus resulting from cesarean section.

Adult↗
PubMed2001

Effect of chromium supplementation and exercise on body composition, resting metabolic rate and selected biochemical parameters in moderately obese women following an exercise program.

OBJECTIVE: To investigate the effect of chromium picolinate (CP) supplementation on body composition, resting metabolic rate (RMR), selected biochemical parameters and iron and zinc status in moderately obese women participating in a 12-week exercise program. METHODS: Forty-four women, 27 to 51 years of age, were randomly assigned to two groups based on their body mass index. Subjects received either 400 microg/day of chromium as a CP supplement or a placebo in double-blind fashion and participated in a supervised weight-training and walking program two days per week for 12 weeks. Body composition and RMR were measured at baseline, 6 and 12 weeks. Selected biochemical parameters and iron and zinc status were measured at baseline and 12 weeks. RESULTS: Body composition and RMR were not significantly changed by CP supplementation. No significant differences in fasting plasma glucose, serum insulin, plasma glucagon, serum C-peptide and serum lipid concentrations or in iron and zinc indices were found between the two groups over time. Serum total cholesterol concentration significantly decreased (p = 0.0016) over time for all subjects combined, probably as a result of the exercise training. Exercise training significantly reduced total iron binding capacity (TIBC) by 3% for all subjects combined (p = 0.001 1). CONCLUSIONS: Twelve weeks of 400 microg/day of chromium as a CP supplement did not significantly affect body composition, RMR, plasma glucose, serum insulin, plasma glucagon, serum C-peptide and serum lipid concentrations or iron and zinc indices in moderately obese women placed on an exercise program. The changes in serum total cholesterol levels and TIBC were a result of the exercise program.

Adult↗
PubMed2001

Protective mechanisms induced by a Japanese encephalitis virus DNA vaccine: requirement for antibody but not CD8(+) cytotoxic T-cell responses.

We have previously shown that a plasmid (pE) encoding the Japanese encephalitis virus (JEV) envelope (E) protein conferred a high level of protection against a lethal viral challenge. In the present study, we used adoptive transfer experiments and gene knockout mice to demonstrate that the DNA-induced E-specific antibody alone can confer protection in the absence of cytotoxic T-lymphocyte (CTL) functions. Plasmid pE administered by either intramuscular or gene gun injection produced significant E-specific antibodies, helper T (Th)-cell proliferative responses, and CTL activities. Animals receiving suboptimal DNA vaccination produced low titers of anti-E antibodies and were only partially or not protected from viral challenge, indicating a strong correlation between anti-E antibodies and the protective capacity. This observation was confirmed by adoptive transfer experiments. Intravenous transfer of E-specific antisera but not crude or T-cell-enriched immune splenocytes to sublethally irradiated hosts conferred protection against a lethal JEV challenge. Furthermore, experiments with gene knockout mice showed that DNA vaccination did not induce anti-E titers and protective immunity in Igmu(-/-) and I-Abeta(-/-) mice, whereas in CD8alpha(-/-) mice the pE-induced antibody titers and protective rate were comparable to those produced in the wild-type mice. Taken together, these results demonstrate that the anti-E antibody is the most critical protective component in this JEV challenge model and that production of anti-E antibody by pE DNA vaccine is dependent on the presence of CD4(+) T cells but independent of CD8(+) T cells.

Adoptive Transfer↗
PubMed2001

Prenatal diagnosis of persistent fetal bradycardia: report of four cases.

Persistent fetal bradycardia is infrequent in prenatal life and difficult to manage optimally. It is generally attributable to sinus bradycardia due to fetal distress, blocked atrial extrasystoles, and congenital complete heart block. We reported four cases of persistent fetal bradycardia from 1995 to 1999 in our hospital. The first, second, and third cases of sustained fetal bradycardia had congenital complete heart block with positive titers for anti-Ro/SSA antibodies in both mothers and fetuses. Because of progressive fetal hydrops in the second case, the pregnancy was terminated. The first and third cases were isolated congenital complete heart block without structural anomaly. After prenatal examination the babies were followed up closely until term and both had a good prognosis without any implantation of pacemaker. In the fourth case there was no clinically known etiology associated with sustained fetal bradycardia. The fetal heart rate returned to normal after 6 weeks of follow-up and the baby was delivered without any cardiac problems. Congenital complete heart block is the most common cause of persistent fetal bradycardia. Prenatal detailed monitoring until delivery is necessary before heart failure develops. Treatment strategies (corticosteroids, ritodrine, and plasmapheresis) are debatable and may include prophylactic therapy for high-risk pregnant women.

Adrenal Cortex Hormones↗
PubMed2001

[Culture of human muscle satellite cell].

OBJECTIVE: To investigate the biological characteristics of human muscle satellite cell cultured in vitro. METHODS: Human muscle satellite cells were obtained from skeletal muscle biopsies of six patients during corrective orthopedic surgery, cultivated in growth medium for ten days, then in differentiation medium for additional five days. Human satellite cells were identified with monoclonal antibody against desmin. Cells were observed under phase contrast microscopy. RESULTS: Human muscle satellite cells proliferated in growth medium, and fused to form myotubes in differentiation medium. After 24 hours in differentiation medium, the confluent satellite cells began to fuse actively and achieved the top level at 72 hours. CONCLUSION: Human muscle satellite cell can proliferate and differentiate in appropriate culture condition. Immunocytochemical detection of desmin is the effective early method to determine satellite cell.

Adolescent↗
PubMed2001

Isolated craniosynostosis: prenatal ultrasound of scaphocephaly with polyhydramnios.

Craniosynostosis is an abnormal shape or dimension of the skull caused by premature closure of one or more skull sutures. It includes scaphocephaly, brachycephaly, oxycephaly, plagiocephaly, trigonocephaly, turricephaly, and a cloverleaf-shaped head. The only cases of craniosynostosis that have been reported concern fetuses with complex and marked craniosynostosis syndromes such as acrocraniofacial dysostosis, Apert's syndrome, Beare-Stevenson cutis gyratum syndrome, Calabro's syndrome, etc. Isolated or simple craniosynostosis, however, is a developmental anomaly rarely found on routine ultrasound examination. We present a case that was diagnosed as scaphocephaly with moderate polyhydramnios by prenatal ultrasound. No other structural anomaly was detected, and the karyotyping was normal. So isolated sagittal craniosynostosis was diagnosed prenatally and was confirmed by postnatal skull radiography as well as 3-dimensional computed tomography. The infant underwent bilateral parietal craniectomy at the age of 3 months. He obtained a good result with no mental problems 4 years after the operation. To our knowledge, this is the second report on the prenatal detection of an isolated form of craniosynostosis.

Adult↗
PubMed2000

Order-disorder transition in bilayers of diphytanoyl phosphatidylcholine.

A comparative study on bilayers of diphytanoyl phosphatidylcholine (DPhPC) and bilayers of dimyristoyl phosphatidylcholine (DMPC) was made by X-ray lamellar diffraction as a function of temperature and the degree of hydration. An order-disorder phase transition of DPhPC reveals an interesting contrast to the standard model of DMPC. Electron density profiles allow us to deduce the conformational changes which occur in the headgroup-glycerol region and in the chain region. The important conclusion is that the lipid headgroup may have different conformational energetics in lipids of different chains. We explain why this is important to protein-membrane interactions.

Dimyristoylphosphatidylcholine↗
PubMed2000

Action of antimicrobial peptides: two-state model.

The argument and experimental evidence are presented for a two-state model that explains the action of both helical and beta-sheet antimicrobial peptides after they bind to the plasma membranes of cells. Each peptide has two distinct physical states of binding to lipid bilayers. At low peptide-to-lipid ratios (P/L), the peptide tends to adsorb in the lipid headgroup region in a functionally inactive state. At a P/L above a threshold value P/L, the peptide forms a multiple-pore state that is lethal to a cell. The susceptibility of a cell to an antimicrobial peptide depends on the value of P/L that is determined by the lipid composition of the cell membrane. This model provides plausible explanations for the experimental findings that the susceptibility of different bacteria to a peptide is not directly correlated to its binding affinity, different peptides preferentially kill different pathogens, and peptides exhibit varying levels of lytic activity against different eukaryotic cells.

Adsorption↗
PubMed2000

cDNA cloning of pig testicular lactate dehydrogenase-C, thermal stability of the expressed enzyme, and polymorphism among strains.

Pig testicular lactate dehydrogenase-C (LDHC) cDNA was cloned and sequenced. The deduced sequence of 332 amino acids from pig LDHC shows 73% and 67% identity with that of pig LDHA (muscle) and LDHB (heart) respectively, whereas pig LDHA and LDHB isozymes shows 74% sequence identity. Pig and mouse LDHC cDNAs were subcloned into bacterial expression vector, and the expressed pig LDHC isozyme was shown to be as thermally stable as mouse LDHC isozyme. Pig genomic DNAs from Chinese Meishan, English Yorkshire, Danish Landrace and American Duroc were shown to exhibit polymorphic sites for restriction enzymes EcoRI, BamHI and PstI.

Animals↗
PubMed2000

Membrane thinning effect of the beta-sheet antimicrobial protegrin.

Lipid bilayers containing the antimicrobial peptide protegrin-1 (PG-1) were studied by lamellar X-ray diffraction. Previously, we have shown that the peptide exists in two distinct states when associated with lipid bilayers depending on the peptide concentration [Heller, W. T., Waring, A. J., Lehrer, R. I., and Huang, H. W. (1998) Biochemistry 37, 17331-17338]. For concentrations below a lipid-dependent threshold, PG-1 exhibits a unique oriented circular dichroism spectrum called the S state. X-ray experiments show that in this state PG-1 decreases the thickness of the lipid bilayer in proportion to the peptide concentration, similar to alamethicin's membrane thinning effect. This indicates that the S state is adsorbed in the headgroup region of the lipid bilayer, where the peptide is in an inactive state. For PG-1 above the threshold concentration, X-ray diffraction shows that the interaction between the peptide and the bilayer changes significantly. These results suggest that PG-1 has the same concentration-gated mechanism of action as alamethicin.

Alamethicin↗
PubMed2000

Crystallization of antimicrobial pores in membranes: magainin and protegrin.

Membrane pores spontaneously formed by antimicrobial peptides in membranes were crystallized for the first time by manipulating the sample hydration and temperature. Neutron diffraction shows that magainins and protegrins form stable pores in fully hydrated fluid membranes. At lower hydration levels or low temperature, the membrane multilayers crystallize. In one crystalline phase, the pores in each bilayer arrange in a regular hexagonal array and the bilayers are stacked into a hexagonal ABC lattice, corresponding to the cubic close-packed structure of spheres. In another crystalline phase, the bilayers are modulated into the rippled multilamellae, corresponding to a 2D monoclinic lattice. The phase diagrams are described. Crystallization of the membrane pores provides possibilities for diffraction studies that might provide useful information on the pore structures.

Amino Acid Sequence↗
PubMed2000

The independent effects of gravity and inertia on running mechanics.

It is difficult to distinguish the independent effects of gravity from those of inertia on a running animal. Simply adding mass proportionally changes both the weight (gravitational force) and mass (inertial force) of the animal. We measured ground reaction forces for eight male humans running normally at 3 m s(-)(1) and under three experimental treatments: added gravitational and inertial forces, added inertial forces and reduced gravitational forces. Subjects ran at 110, 120 and 130 % of normal weight and mass, at 110, 120 and 130 % of normal mass while maintaining 100 % normal weight, and at 25, 50 and 75 % of normal weight while maintaining 100 % normal mass. The peak active vertical forces generated changed with weight, but did not change with mass. Surprisingly, horizontal impulses changed substantially more with weight than with mass. Gravity exerted a greater influence than inertia on both vertical and horizontal forces generated against the ground during running. Subjects changed vertical and horizontal forces proportionately at corresponding times in the step cycle to maintain the orientation of the resultant vector despite a nearly threefold change in magnitude across treatments. Maintaining the orientation of the resultant vector during periods of high force generation aligns the vector with the leg to minimize muscle forces.

Adult↗