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Biomedical subjects

K F Yip

Publications and source records attributed to K F Yip.

At least 19 recordsLinked to original sources
PubMed2006

A simple and secure method to fix laparoscopic trocars in children.

We introduce a simple method of fixing trocars to the abdominal wall in children. Before anchoring the trocar, a piece of Tegaderm polyurethrane adhesive (3M Healthcare, St. Paul, Minnesota) is attached to the trocar. A silk stitch is anchored to neighboring skin, and then transfixed over the shaft of the trocar through the adhesive. Both inward and outward movement of the trocar can be restrained. This method is simple, fast, secure, and can be applied to trocars of any size.

Abdominal Wall↗
PubMed2004

Evolutionary minority game wtih multiple options.

We propose and study an evolutionary minority game (EMG) in which the agents are allowed to choose among three possible options. Unlike the original EMG where the agents either win or lose one unit of wealth, the present model assigns one unit of wealth to the winners in the least popular option, deducts one unit from the losers in the most popular option, and awards R (-1 R(c), where R(c) (N) is a critical value for optimal performance of the system that drops to zero as the number of agents N increases.

Journal Article↗
PubMed2004

Laparoscopic flip-flap hernioplasty: an innovative technique for pediatric hernia surgery.

BACKGROUND: Laparoscopic hernia repair is especially advantageous for bilateral or recurrent diseases in children because it avoids vas injury. However, it is more technically demanding, and the recurrent rate has been higher than with the open method. The authors developed a method of laparoscopic hernia repair that is easy and secure. METHODS: The hernia opening was repaired with a peritoneal flip-flap anchored with a single tension-free intracorporeal suture. The vas and testicular vessel were completely untouched. The valve mechanism of the flip-flap helped to avoid scrotal collection and prevent hernia recurrence. RESULTS: In 32 patients ages 1 month to 17 years 43 repairs were performed. The early result was promising, and no recurrence was noticed in a median follow-up period of 4 months. CONCLUSIONS: Laparoscopic flip-flap hernioplasty is easy to perform and has a number of theoretical advantages, although the long-term result still needs to be evaluated.

Adolescent↗
PubMed2004

Enhanced winning in a competing population by random participation.

We study a version of the minority game in which one agent is allowed to join the game in a random fashion. It is shown that in the crowded regime, i.e., for small values of the memory size m of the agents in the population, the agent performs significantly well if she decides to participate the game randomly with a probability q and she records the performance of her strategies only in the turns that she participates. The information, characterized by a quantity called the inefficiency, embedded in the agent's strategies performance turns out to be very different from that of the other agents. Detailed numerical studies reveal a relationship between the success rate of the agent and the inefficiency. The relationship can be understood analytically in terms of the dynamics in which the various possible histories are being visited as the game proceeds. For a finite fraction of randomly participating agents up to 60% of the population, it is found that the winning edge of these agents persists.

Journal Article↗
PubMed2000

Laparascopy for definitive diagnosis and treatment of gastrointestinal bleeding of obscure origin in children.

BACKGROUND/PURPOSE: Gastrointestinal bleeding (GIB) in children with no identifiable source found after upper endoscopy and colonoscopy or GIB of obscure origin can pose a great management problem for pediatric surgeons. The recent advent of laparoscopy in children has provided a useful solution. METHODS: The authors reviewed their experience of using laparoscopy in the management of 17 children (13 boys) with GIB of obscure origin over an 8-year period. The mean age was 9.8 years (range, 3 to 17 years). RESULTS: In all patients, upper endoscopy and colonoscopy results did not show a bleeding source. Pertechnetate technetium Tc 99m scan showed positive uptake in 6 patients. Of these, 4 were found on laparoscopy to have a Meckel's diverticulum, 1 had intestinal duplication, and the remaining patient had nodular lymphoid hyperplasia at the terminal ileum. Ten patients had a negative pertechnetate scan. Of these, 3 had a Meckel's diverticulum, 1 had lymphoid hyperplasia, 1 had intestinal duplication, 1 had vascular enteritis, and 4 had normal findings on videolaparoscopy. Pertechnetate scan was not performed in 1 patient and, on laparoscopy, it turned out to be Meckel's diverticulum. Laparoscopic-assisted small bowel resection was performed successfully in all patients with Meckel's diverticulum, intestinal duplication, and nodular hyperplasia. Conversion to open surgery was required in the patient with extensive ileal vascular enteritis secondary to Henoech Scholein purpura. All patients, including the 4 with normal findings on laparoscopy, had made uneventful recovery without further episode of bleeding. CONCLUSION: Laparoscopy is a useful diagnostic as well as therapeutic tool in children with GIB of obscure origin.

Adolescent↗
PubMed1997

Laparoscopic appendectomy in paediatric patients: optimization with a new method of port insertion.

BACKGROUND: Conventional methods of port insertion for laparoscopic appendectomy often result in poor surgical access, especially when a pelvic appendix is encountered or when mobilization of the caecum becomes necessary. The relatively small antero-posterior diameter of the peritoneal cavity in children further aggravates this problem. METHODS: We have modified the procedure by inserting only one 10-mm port at the sub-umbilical position, and two 5-mm ports at the lower abdomen beneath the 'bikini line'. The videoscope is inserted via the left lower abdominal port, and the sub-umbilical port and the right lower abdominal port are used as the working ports. RESULTS: Very satisfactory results have been achieved. The bottom of the caecum can be well visualized and caecum mobilization becomes easy. A pelvic appendix is well visualized. Dissection of a high retrocaecal appendix could be carried out without being obscured by the caecum. Better cosmetic results were also achieved. The method has been applied in 66 patients (aged 4-14). The mean operation time was 62 min. CONCLUSION: We recommend this approach to be used as the standard procedure for laparoscopic appendectomy in children.

Adolescent↗
PubMed1987

A solution hybridization assay for ribosomal RNA from bacteria using biotinylated DNA probes and enzyme-labeled antibody to DNA:RNA.

Rapid, convenient and non-isotopic nucleic-acid hybridization methods are needed for this technology to have practical use in clinical diagnostic tests. A method for hybridization of RNA with a DNA probe in solution followed by capture and measurement of the hybrid is described. DNA probes complementary to 23S rRNAs from Escherichia coli and Bacillus subtilis were labeled with a photoactivable biotin reagent. Hybridization of the biotinylated probes with rRNA was complete in less than 5 min. The resultant hybrids were allowed to bind simultaneously to succinylated avidin immobilized on latex and to beta-galactosidase-labeled Fab' fragments of a monoclonal antibody-specific for DNA:RNA. Finally, beta-galactosidase associated with the captured hybrids was measured colorimetrically. The hybridization method can detect less than 1000 bacteria per assay and has broad specificity to permit detection of the various genera of bacteria that infect the urinary tract.

Animals↗
PubMed1980

Syntheses of some fluorescent ribonucleotides.

Synthesis of guanosine 3'-phosphodiesters of 1, N6-ethenoadenosine-2-sulfonate or 1, N6-etheno-2-azaadenosine can be done readily with ribonuclease N1. There is a 10-fold difference in quantum yield between the phosphodiesters and the starting fluorescent nucleosides. This difference provides the basis for the development of a fluorescent assay for nuclease.

Adenosine↗
PubMed1977

Perfusion and molecular modification of idoxuridine to alter its cerebrospinal fluid metabolism.

Two methods to deter the rapid intrathecal degradation of idoxuridine were investigated: (a) rapid drug perfusion through the ventricular system, and (b) modification of the molecule to its uronic acid derivative, 2'-deoxy-5-iodo-5'-uridinecarboxylic acid, to make it less susceptible to enzymatic digestion. Perfusion of idoxuridine through the ventricular system (ventriculocisternal) of dogs at 0.97 ml/min saturated the metabolic pathway so that the outflow solution yielded a single spot (Rf 0.76) on TLC indicative of the intact molecule. The 125I-labeled uronic acid was synthesized from the 125I-labeled parent compound, and the labeled compounds were compared after their individual intracisternal injection in dogs. Since there was no difference in the disappearance rates, the stability of the uronic acid was, in fact, no greater than that of the parent compound in vivo. Ventricular perfusion of idoxuridine, however, seems a suitable means for increasing the amount of active drug delivered to central nervous system tumors and viral infections.

Animals↗
PubMed1976

Effect of deoxyribonuclease on adriamycin-polynucleotide complexes.

Recent interest in the use of adriamycin-DNA complex as an approach to improve the therapeutic effectiveness and to reduce toxicity of adriamycin for cancer chemotherapy requires an in-depth understanding of the physicochemical and biochemical properties of such complexes. The interactions of adriamycin with single-strand polydeoxyribonucleotides, double-strand DNA, and double-strand ribodeoxyribopolynucleotide hybrids were therfore investigated. Association constants (Kapp) of adriamycin and polynucleotides were obtained. These data showed that the inherent variable in such complex lies in the composition of the polynucleotides. Alternate deoxyguanylate (dG)-deoxycytidylate (dC) sequence binds 7-fold better than alternate deoxyadenylate (dA)-deoxythymidylate (dT) sequence. Comparative studies of the hydrolysis of DNA duplexes by deoxyribonucleases I and II with and without adriamycin were also carried out. The rate of hydrolysis decreased in the order poly(dA-dT) greater than calf thymus DNA greater than poly(dG-dC) greater than poly(dA)-poly(dT) greater than poly(dG)-poly(dC) for DNase I and poly(dA)-dT) greater than calf thymus DNA greater than poly(dG-dC) greater than poly(dA)-poly(dT) greater than poly(dG)-poly(dC) for DNase II. Intercalation of adriamycin to deoxyribopolynucleotide duplex resulted in inhibition of DNase II two to three times more than tat of DNase I. On the other hand, intercalation of adriamycin to homodeoxypolynucleotide duplex poly(dA)-poly(dT) and poly(dG)-poly(dC) enhanced the DNase I hydrolysis. If DNase I activity could be related to serum DNase and DNase II related to tumor lyososomal DNase as in the endocytosis mechanism proposed by Trouet et al. (Cancer Chemotherapy Rept., 59: 260, 1975), the best adriamycin carrier suggested by this investigation could be poly(dA)-poly(dT) and poly(dG-dC). It is also suggested in this study that adriamycin-RNA-DNA hybrid could be of interest as an antiviral agent by a similar release mechanism via RNase H, an enzyme associated with viral reverse transcriptase.

Animals↗