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Biomedical subjects

H K Choi

Publications and source records attributed to H K Choi.

At least 91 records · Page 5Linked to original sources
PubMed1996

An open clinical trial of fluoxetine in the treatment of premature ejaculation.

There have been an increased number of recent reports on orgasm-related sexual dysfunction coincident with selective serotonin reuptake inhibitor (SSRI) treatment. In contrast, it has also been reported that SSRIs improve sexual dysfunction. Low doses of clomipramine and paroxetine, potent 5-hydroxytryptamine reuptake blockers, have been found to retard ejaculation time. We hypothesized that the SSRI fluoxetine might be effective in treating premature ejaculation. In an 8-week open-label clinical study, 11 male patients with premature ejaculation were treated with fluoxetine. After a washout period of 2 weeks, each patient was assigned to receive fluoxetine, 20 mg/day for 2 weeks, and then titrated to 60 mg/day, depending on the patient's tolerability and clinical response. A within-subjects comparison of pre- and posttreatment intravaginal ejaculation latency time revealed a significant improvement. Fluoxetine treatment produced significant improvements in self-visual analogue scale scores for sexual desire, anxiety for rapid ejaculation, and partner's satisfaction with ejaculation and overall sexual function. These data suggest that serotonergic antidepressants may be effective in treating rapid ejaculation in men and underline the need to carry out a double-blind, placebo-controlled trial to confirm these results.

Adult↗
PubMed1996

The effects of SS-cream and its individual components on rabbit corpus cavernosal muscles.

SS-cream (Severance Secret cream) is made up of extracts from 9 natural products for treating premature ejaculation (PE). SS-cream has been proved to be effective in the treatment of PE in pilot clinical studies. It has also been found to have a potentiating effect of their erectile capacity in some patients. Therefore, we investigated the pharmacological actions of SS-cream and the extracts of its individual components in rabbit corpus cavernosal smooth muscle to realize the effect of SS-cream on penile erection. Extracts of Bufonis Venenum induced a dose-related contraction of rabbit corpus cavernosal muscle, which was significantly inhibited by phentolamine. Extracts of Caryophylli Flos induced a dose-related relaxation in the muscle strips precontracted with phenylephrine (5 x 10(-6)M; PHE). Caryophylli Flos caused a dose-dependent inhibition of the PHE induced contraction and also inhibited the contractility of Bufonis Venenum. Other extracts, when used individually or in a mixture, induced a dose-related relaxation in the precontracted muscle strips with PHE. SS-cream began to exert a relaxing effect at the concentration of 0.05 mg/ml in the muscle strips precontracted muscle strips with PHE (5 x 10(-6)M); causing dose-dependent relaxation with a maximal effect at 0.2 mg/ml. The relaxation effect of SS-cream was partially inhibited by endothelial disruption and by pretreatment with methylene blue, pyrogallol, atropine, and indomethacin, although they were not statistically significant. The results show that SS-cream has a relaxing effect on cavernosal smooth muscle. And it is partly related with enhancing the NO/cyclic GMP pathway although the relaxation mechanism in detail remains to be elucidated. Therefore, SS-cream may be effective for future treatment of mild erectile dysfunction, in addition to its role for premature ejaculation.

Animals↗
PubMed1996

Penile sensitivity in patients with primary premature ejaculation.

PURPOSE: We investigated penile sensory levels in patients with primary premature ejaculation to determine whether there is an etiological basis for this condition. MATERIALS AND METHODS: Penile biothesiometry was performed in 120 patients with primary premature ejaculation without erectile dysfunction and neurological deficit, and in 66 normal potent male volunteers. Vibratory thresholds were recorded at the glans penis, penile shaft, scrotum and index finger using a biothesiometer. RESULTS: On the glans penis and penile shaft the values in patients with premature ejaculation were significantly less than those in normal potent men (p < 0.001). In normal potent men an age dependency of biothesiometric parameters was noted, with a significant increase in vibratory threshold at the glans penis and penile shaft in older patients. However, in patients with premature ejaculation there were consistently decreased values without age dependency at the glans penis and penile shaft (p > 0.05). CONCLUSIONS: Patients with primary premature ejaculation have penile hypersensitivity, which provides further implications for an organic basis of premature ejaculation.

Adult↗
PubMed1995

cDNA cloning and gene expression of lebocin, a novel member of antibacterial peptides from the silkworm, Bombyx mori.

A cDNA encoding lebocin, a novel member of insect antibacterial peptides, was isolated from the fat body cDNA library of Bombyx mori larvae immunized with Escherichia coli. The cDNA was 844 bp long and had an open reading frame (ORF) containing a probable signal peptide (16 amino acids), a putative prosegment (104 amino acids) and a mature peptide (32 amino acids) followed by 27 additional amino acids at its carboxyl-terminus. Northern blot analysis showed that lebocin gene expression was inducible by bacterial injection, occurred tissue-specifically in the fat bodies and continued at least for 48 h post-infection. These results suggest that lebocin has a unique precursor structure and shows typical gene expression pattern as insect antibacterial peptide.

Amino Acid Sequence↗
PubMed1995

Intermittent plasma growth hormone triggers tyrosine phosphorylation and nuclear translocation of a liver-expressed, Stat 5-related DNA binding protein. Proposed role as an intracellular regulator of male-specific liver gene transcription.

Growth hormone (GH) exerts sexually dimorphic effects on liver gene transcription that are regulated by the temporal pattern of pituitary GH release, which is intermittent in male rats and nearly continuous in females. To investigate the influence of these GH secretory patterns on intracellular hepatocyte signaling, we compared the pattern of liver nuclear protein tyrosine phosphorylation in male and female rats. An M(r) approximately 93,000 polypeptide, p93, was found to be tyrosine phosphorylated to a high level in male but not female rats. GH, but not prolactin, rapidly stimulated p93 tyrosine phosphorylation in hypophysectomized rats. Intermittent plasma GH pulses triggered repeated p93 phosphorylation, while continuous GH exposure led to desensitization and a dramatic decline in liver nuclear p93. p93 was cross-reactive with two monoclonal antibodies raised to mammary Stat 5, whose tyrosine phosphorylation is stimulated by prolactin. Intermittent GH pulsation translocated liver Stat 5/p93 protein from the cytosol to the nucleus and also activated its DNA binding activity, as demonstrated using a mammary Stat 5-binding DNA element derived from the beta-casein gene. p93 is thus a liver-expressed, Stat 5-related DNA binding protein that undergoes tyrosine phosphorylation and nuclear translocation in response to intermittent plasma GH stimulation and is proposed to be an intracellular mediator of the stimulatory effects of GH pulses on male-specific liver gene expression.

Animals↗
PubMed1995

Nucleocapsid and glycoprotein organization in an enveloped virus.

Alphaviruses are a group of icosahedral, positive-strand RNA, enveloped viruses. The membrane bilayer, which surrounds the approximately 400 A diameter nucleocapsid, is penetrated by 80 spikes arranged in a T = 4 lattice. Each spike is a trimer of heterodimers consisting of glycoproteins E1 and E2. Cryoelectron microscopy and image reconstruction of Ross River virus showed that the T = 4 quaternary structure of the nucleocapsid consists of pentamer and hexamer clusters of the capsid protein, but not dimers, as have been observed in several crystallographic studies. The E1-E2 heterodimers form one-to-one associations with the nucleocapsid monomers across the lipid bilayer. Knowledge of the atomic structure of the capsid protein and our reconstruction allows us to identify capsid-protein residues that interact with the RNA, the glycoproteins, and adjacent capsid-proteins.

Freezing↗
PubMed1995

Occurrence of novel types of nitric oxide synthase in the silkworm, Bombyx mori.

Nitric oxide (NO) synthase activity was detected in fat body and the Malpighian tubles of the silkworm, Bombyx mori. Main NO synthase activity in the fat body was Ca(2+)/calmodulin-dependent, inducible by bacterial lipopolysaccharide (LPS) and required NADPH, FAD, FMN, dithiothreitol (DTT) and tetrahydrobiopterin (BH4) as cofactors for the full expression of the activity. The Malpighian tubles contained two types of NO synthase. One was Ca(2+)-independent, calmodulin-dependent and constitutive and the other was Ca(2+)-dependent and constitutive. The former NO synthase required the same cofactors as fat body NO synthase. The activity of Malpighian tuble NO synthases increased dramatically at the end of the last instar period, just prior to spinning. These results indicate that B. mori contains new types of NO synthase, suggesting the wide distribution and different characteristics of this enzyme among vertebrates and invertebrates.

Amino Acid Oxidoreductases↗
PubMed1995

Percutaneous absorption and dermal delivery of cyclosporin A.

The present study deals with attempts to deliver cyclosporin A into the deeper skin and some of the fundamental reasons why this proves so difficult. Because of different physicochemical requirements for the solution and activity of cyclosporin A and the enhancer, n-decylmethyl sulfoxide, it was hard to demonstrate increases in permeation of cyclosporin A by the enhancer in either aqueous or ethanol/water formulation. Cyclosporin A was prohibitively insoluble in aqueous media and the activity of the enhancer is diminished to ineffectiveness when it is applied in alcoholic media. However, n-decylmethyl sulfoxide action on the stratum corneum could be obtained by pretreating the skin. The effect of pretreatment with this compound on the permeation of cyclosporin A through hairless mouse skin and human skin was studied with side-by-side diffusion cells. The skin was pretreated with 10 mM n-decylmethyl sulfoxide for various durations. Cyclosporin A in an ethanol/water formulation was then placed in the donor cell, with the amount of ethanol being controlled to maintain the highest possible thermodynamic activity. Accumulations of cyclosporin A in receiver cell media, aqueous or ethanol/water, were then assessed. Permeation from two different concentrations of cyclosporin A was compared. The permeability of hairless mouse skin to cyclosporin A was increased by the pretreatment, but results with human skin were more equivocal. It appears that it will take very long pretreatments to ready human skin for topical cyclosporin A therapy.

Administration, Cutaneous↗
PubMed1995

Sensory evoked potential and effect of SS-cream in premature ejaculation.

The cause of premature ejaculation (PE) has been thought to be psychological in the majority of patients but we investigated penile hypersensitivity for an organic basis of PE. For another organic basis of PE, we have suggested hyperexcitability of the ejaculation center. SS-cream is a topical agent containing 9 oriental herbs for treating PE. Clinically SS-cream has been effective in the treatment of PE. Therefore, in order to implicate the organic basis of PE and realize the effect of SS-cream on PE, we investigated the somatosensory evoked potential (SEP) in patients with PE(16 cases) and the effects of SS-cream on SEP for treating PE. The latencies and amplitudes of the evoked responses were measured by two different places in stimuli, one was on the penile shaft with ring electrode and the other on the glans penis with a surface electrode. The latency of SEP stimulated at the glans penis was significantly longer than that stimulated at the penile shaft (p < 0.05). The latency stimulated at the glans penis after applying SS-cream was significantly longer than before applying SS-cream (p < 0.05), which was near the level of a normal potent man. But the latency stimulated at the penile shaft has no significant difference between before and after the application of SS-cream (P > 0.05). The amplitudes of the evoked responses stimulated at the glans penis were significantly higher than those stimulated at penile shaft (p < 0.05). And both these amplitudes were significantly reduced with the application of SS-cream (p < 0.05). With these result, we can suggest that the patients with PE have glans penile hyperexcitability and it provides further implications for an organic basis of PE, SEP stimulated at the glans penis can be a very useful method to evaluate PE, along with SEP stimulated a penile shaft and SS-cream prolongs the sensory conduction and reduces the penile hyperexcitability of the patient with PE.

Adult↗
PubMed1995

Grading of transitional cell bladder carcinoma by image analysis of histological sections.

Image analysis of histological sections was used to achieve a more objective malignancy grading of transitional cell carcinoma of the bladder. Images from Feulgen-stained sections from a clinical material of 197 tumours were analyzed. Features at various levels of analysis, e.g. mainly related to individual objects, neighbouring objects and the entire image, were analyzed. The features used were based on relational rather than individual nuclear features. With this technique, typical tissue architecture and degree of order/disorder can be described. These characteristics were compared by means of multivariate statistical methods with the subjective grading of the pathologists at our institution. This comparison provided the best subset of features and the agreement between the subjective and computer-based classification was 73%. The size, orientation and variation of the grey scale of the nuclei were particularly powerful. On a continuous scale, from grade 1 to 2A and 2B to 3, the four grades formed two distinct classes, low and high grade. In this distribution, the intermediate grade 2A was identified as a displaced grade 1 and the other intermediate grade 2B as a displaced grade 3.

Carcinoma, Transitional Cell↗
PubMed1995

Clinical efficacy of Korean red ginseng for erectile dysfunction.

To investigate the efficacy in treating erectile dysfunction and to develop a natural drug without complications, the results of ginseng treatments are compared to placebo and other drug. A total of 90 patients with 30 patients in each group were closely followed. Changes in symptoms such as frequency of intercourse, premature ejaculation, and morning erections after treatment were not changed in all three groups (p > 0.05). However in the group receiving ginseng, changes in early detumescence and erectile parameters such as penile rigidity and girth, libido and patient satisfactions were significantly higher than that of other groups (p < 0.05). The overall therapeutic efficacies on erectile dysfunction were 60% for ginseng group and 30% for placebo and trazodone treated groups, statistically confirming the effect of ginseng (p < 0.05). No complete remission of erectile dysfunction was noted, but partial responses were reported. No cases of aggravation of symptoms were reported. AVS-penogram, which is a recording of penile hemodynamic changes during the natural erection after audiovisual erotic stimulation, is not changed after administration of ginseng. However if administered for a prolonged period of time, the cummulative effect on vascular flow might be seen. The administration of Korean red ginseng has shown to have superior effects compared to the placebo or trazodone. Definitely more researches are required to elucidate the mechanism of ginseng. The effects of saponin, extracted from ginseng, on smooth muscle of erectile tissues, can be evaluated using organ chamber or nitric oxide titration, thereby pinpointing the exact action mechanism of saponin. As more informations are available, possible breakthrough in treatment of erectile dysfunction could be arisen from active saponin extracted from red ginseng, bringing hopes to many sufferers of erectile dysfunction.

Adult↗
PubMed1994

Ten years of experience with various penile prosthesis in Korean.

Currently there are more than 10 types of penile prosthesis available, ranging from the very simple to the very sophisticated. We review our experiences with various penile prosthesis, with particular regard to the complication rate. From Dec. 1983 to Jul. 1993, we implanted 295 penile prosthesis of eight different types. The average age of patients was 44 years. Every patient was evaluated with various multidisplinary diagnostic approaches. The etiologies of impotence were vasculogenic 29%, diabetogenic 22%, spinal cord injury 16%, pelvic bone injury 11%, etc. The types of implanted prosthesis were AMS malleable 143, Jonas 42, Dynaflex 36, Hydroflex 8, Uni-Flate 1000 2, AMS 700 CXM 58, Ultrex 3, Mentor alpha-1 3 and the mean follow-up period was 34 months. The diameters of implanted prosthesis were from 9.5 mm to 13 mm, mostly 9.5 mm (52.9%). The length of implanted prosthesis were from 10 cm to 20 cm, mostly 16 approximately 18 cm (68.8%). Cases with uneven diameters or lengths were 20 (6.8%). The int aoperative complications were 1 corporeal rupture and 1 bladder rupture, and the postoperative complications were 2 prosthesis infections, 2 mechanical failures, and 1 prosthesis infection with mechanical failure. In those 4 patients reimplantations were successful. More than 99% (290/291) patients still have functioning prosthesis. Every prosthesis has their advantages and disadvantages. Factors to be analysed in the selection of proper prosthesis should include patients economic status, education, personality, social activity, hand dexterity, and penile size.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Psychogenic versus primary organic impotence.

The origin of impotence in unmarried patients is believed to be mostly psychogenic and has been diagnosed as such. However, we occasionally found that some of these patients showed clinical findings strongly suggesting an organic cause. We investigated the clinical spectrums of 160 unmarried impotent patients (145 psychogenic impotent patients and 15 primary organic impotent patients). The primary organic impotent patients had a history of unsuccessful sustained erections and intercourse without any trauma or definite associated medical disease, and showed abnormal findings in the audiovisual stimulation penogram (AVS-penogram), whereas only 66% (96/145) of the psychogenic group showed abnormal classification. The most common cause of primary organic impotence was vasculogenic. Primary organic impotence should be considered a specific disease for which comprehensive diagnostic methods are needed in unmarried impotent patients to differentiate it from psychogenic impotence.

Adult↗
PubMed1994

Grading of transitional cell bladder carcinoma by texture analysis of histological sections.

Conventional subjective visual grading of malignancy in bladder carcinoma suffers from poor standardization. In an attempt to improve this by image analysis we carried out a texture analysis of a total of 197 images from Feulgen-stained histological tissue sections. The textural features used were based on the spatial gray-tone co-occurrence probability matrices for step-lengths 3, 4 and 6 pixels. These features were compared to the subjective grading by multivariate statistical methods. Using a two-stage hierarchical classifier 84.3% agreement was obtained between the subjective and computer-based classification. This was verified through the jackknifed classification technique.

Carcinoma, Transitional Cell↗
PubMed1993

Dopaminergic neurons grown in three-dimensional reaggregate culture for periods of up to one year.

The use of three-dimensional (3-D) reaggregate cultures of mesencephalic fetal dopaminergic neurons in co-culture with their target cells of the corpus striatum (CS) has permitted examination of the development and survival of such neurons for periods of up to 1 year. Dopaminergic neurons grown in dialyzed serum in reaggregate cultures show an increase in neurotransmitter level over the first 2 months in culture, and these levels of dopamine are maintained or increased over the next 4-12 months. While there is an apparent decrease in the numbers of dopaminergic neurons by 1 year in culture, many dopaminergic neurons survive and can be visualized at the light and electron microscopic level by tyrosine hydroxylase immunocytochemistry and their processes assessed by histofluorescent techniques. The survival of dopaminergic neurons in an organized culture system in which they demonstrate a normal developmental pattern and establish synaptic contact with appropriate target cells provides an approach to the experimental examination of a substantial portion of the life history of these neurons.

Animals↗
PubMed1993

Sequence of a cDNA and expression of the gene encoding epidermal and gut chitinases of Manduca sexta.

Insects use chitinolytic enzymes to digest chitin in the exoskeleton during the molting process. We have isolated and sequenced a chitinase-encoding cDNA from the tobacco hornworm, Manduca sexta, compared its sequence with genes encoding chitinolytic enzymes from other sources, and studied chitinase gene expression and hormonal regulation during the larval-pupal transformation. The insert DNA in this clone is 2452 nucleotides long with an open reading frame of 1662 nucleotides that encodes a protein of 554 amino acids with a molecular weight of 62 kDa. Several regions of the amino acid sequence in this protein are similar to sequences in yeast, cucumber and bacterial endo-beta-N-acetylglucosaminidases. Hybrid-selection of mRNA and in vitro translation yielded an immunoreactive protein with an apparent molecular mass of 75 kDa, which is similar to the size of a chitinase present in pharate pupal molting fluid. Southern blot analysis indicated that one or two genes related to the cDNA clone are encoding chitinases in the Manduca genome. The major tissues expressing chitinase genes were the epidermis and gut with mRNA levels highest on c. days 5-7 during the fifth larval instar. Injection of 20-hydroxyecdysone into ligated fifth instar abdomens caused about a 10-fold increase in mRNA levels in both epidermis and gut, and topical application of the juvenile hormone mimic, fenoxycarb, suppressed the ecdysteroid-induced accumulation of chitinase RNA.

Amino Acid Sequence↗
PubMed1992

Specific modulation of dopamine expression in neuronal hybrid cells by primary cells from different brain regions.

MN9D is an immortalized dopamine-containing neuronal hybrid cell line. When MN9D cells were coaggregated with primary embryonic cells of optic tectum, a brain region that does not receive a dopaminergic innervation, there was a marked reduction in their dopamine content, tyrosine hydroxylase immunoreactivity, and tyrosine hydroxylase mRNA. Similar reductions in dopamine content were produced by coaggregation with cells from embryonic thalamus, another brain region devoid of dopaminergic innervation. Coaggregation of MN9D cells with dopaminoceptive cells from the corpus striatum or the cortex did not have a demonstrable stimulatory effect on the dopamine content of MN9D cells. The decrease in MN9D dopamine content produced by optic tectum cells was not reversed by addition of corpus striatum cells. Thus, the MN9D hybrid cells are able to respond to an inhibitory factor(s) from cells derived from brain areas that are not targets for dopaminergic neurons. Catecholamine-producing PC12 cells did not respond in a similar manner, suggesting that the response of MN9D cells is a function of their mesencephalic origin. Given the selective response of MN9D cells to different brain cell populations, this hybrid cell line should facilitate investigations of cell-cell interactions in the central nervous system that may be involved in the expression of neurotransmitter phenotype and establishment of specific neuronal connections.

Animals↗