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Biomedical subjects

B Chang

Publications and source records attributed to B Chang.

At least 145 records · Page 8Linked to original sources
PubMed1994

Safety assessment for the frail elderly: a comparison of restrained and unrestrained nursing home residents.

OBJECTIVE: To facilitate clinicians' judgement concerning physical restraint decisions by identifying potentially reversible injury risk factors that differentiate representative samples of restrained and unrestrained nursing home residents. DESIGN: Comparison of restrained and unrestrained nursing home residents on a safety assessment for the frail elderly (SAFE) protocol. SETTING: Long-term care facilities in the Greater Los Angeles Area. PARTICIPANTS: One hundred eight physically restrained and 111 unrestrained nursing home residents. INTERVENTION: None. MAIN OUTCOME MEASURES: (1) Internal, Interrater, and test/retest reliability of the overall SAFE protocol and of the four major factors measured by SAFE; (2) The relationship of SAFE scores to expert judgment of resident injury risk; (3) Differences between large samples of restrained and unrestrained residents on specific SAFE score factors. RESULTS: Two walking, one transition, and one judgment factor are reliably measured by the SAFE protocol. SAFE scores were significantly correlated with expert judgment of risk for injury and showed large differences between restrained and unrestrained residents, even after differences in ambulation ability between the two groups were accounted for. CONCLUSION: The SAFE is a reliable protocol that measures behavioral factors related to falls and risk for injury among nursing home residents with a broad range of cognitive impairment. Factors that significantly differentiate restrained and unrestrained groups should be targeted for rehabilitation and remediation in physical restraint reduction efforts. Removing or changing restraints for the large sample (50%) of restrained residents who were not ambulatory will not significantly increase their mobility, since the majority of this group could not independently propel their wheelchairs. Increased mobility for the large group of both restrained and unrestrained residents will likely be realized only if restraint reduction programs are combined with interventions to improve both mobility and the specific behavioral performance factors measured by SAFE.

Aged↗
PubMed1994

Electrochemical therapy in the treatment of malignant tumours on the body surface.

From November 1988 to May 1991, 113 patients with malignant tumours on their body surface, who were at great operative risk or had refused surgery, underwent local treatment with electrochemical therapy (ECT). After 2.6 years' follow up, total effective rate of the cure was 79.7%. The clinical results were considered satisfactory.

Adolescent↗
PubMed1994

Retinal degeneration in motor neuron degeneration: a mouse model of ceroid lipofuscinosis.

PURPOSE: To evaluate the retinal degeneration of the motor neuron degeneration (mnd) mouse, and to confirm its inheritance pattern and gene location. METHODS: In screening the mnd/mnd mouse for ocular disease, a retinal degeneration was found that was evaluated by serial electroretinography, histology, electron microscopy, indirect ophthalmoscopy, and genetic and linkage analysis. RESULTS: In homozygous mnd mice, photoreceptor and outer nuclear layers show cell loss by 5 weeks after birth. By 2 months, the peripheral retina is preferentially thinner than central retina, and by 6 months the entire retina is reduced in thickness. The electroretinogram was extinguished by 6 months. Transmission electron microscopy at 3 and 6 months showed distinct cytoplasmic inclusions characteristic of the curvilinear profiles seen in human ceroid lipofuscinosis. Genetic analyses show that the retinal degeneration in mnd mice is inherited as a single autosomal gene with recessive expression, and a three-point cross placed the retinal degeneration at the mnd locus on the proximal end of mouse chromosome 8. Crosses with other known strains with retinal degeneration were normal. CONCLUSIONS. The mnd mouse model is similar to the juvenile onset Spielmeyer-Vogt form of ceroid lipofuscinosis (Batten disease), and provides a good model for the retinal degeneration found in these patients.

Alleles↗
PubMed1994

Malignant mixed tumor (carcinosarcoma) of the pancreas: a case report supporting organ-induced differentiation of malignancy.

BACKGROUND: We present an unusual case of a malignant mixed tumor (carcinosarcoma) of the head of the pancreas that was surgically resected and whose tissue pathologic condition supported the concept of organ-induced differentiation of malignancy. METHODS: After a pancreaticoduodenectomy, tissue sections from various anatomic regions of the tumor were studied by routine histologic examination and immunocytochemistry. Genomic DNA from various regions of the tumor was extracted and digested with Hpa II, and a 511 bp region of the hypoxanthine phosphoribosyltransferase gene was amplified with the polymerase chain reaction to assess clonality. RESULTS: The pathologic findings revealed areas of both adenocarcinoma and leiomyosarcoma, but these disparate areas were not randomly distributed but rather were polar in nature. The adenocarcinomatous areas localized to the tumor within the head of the pancreas, an area of normal ontogenetic glandular development, whereas the leiomyosarcomatous areas localized to regions of the tumor infiltrating the duodenal wall, an area of normal ontogenetic smooth muscle development. Both the adenocarcinomatous and the leiomyosarcomatous areas showed evidence of monoclonality and clonal identity. CONCLUSIONS: This interesting polar distribution of histologic patterns illustrated by this malignant mixed tumor (carcinosarcoma) supports the hypothesis of organ-induced differentiation of malignancy.

Adenocarcinoma↗
PubMed1993

Inhibition of matrix metalloproteinases by N-carboxyalkyl peptides.

An extensive study of the requirements for effective binding of N-carboxyalkyl peptides to human stromelysin, collagenase, and to a lesser extent, gelatinase A has been investigated. These efforts afforded inhibitors generally in the 100-400 nM range for these matrix metalloproteinases. The most significant increase in potency was obtained with the introduction of a beta-phenylethyl group at the P1' position, suggesting a small hydrophobic channel into the S1' subsite of stromelysin. One particular compound, N-[1(R)-carboxyethyl]-alpha(S)-(2-phenylethyl)glycyl-L-leucine,N- phenylamide (79a), is relatively selective for rabbit stromelysin with a K(i) = 6.5 nM and may prove useful for elucidating the role of endogenously-produced stromelysin in lapine models of tissue degradation.

Amino Acid Sequence↗
PubMed1993

Further clinical use of the interposition arteriovenous loop graft in free tissue transfers.

The use of an arteriovenous fistula (AVF) to afford vascular access for free tissue transfer is described in 11 consecutive patients from a 1 year period. The leg was the site of pathology in six cases, and a reversed saphenous AVF to the femoral vessels was created. In the remaining five cases, those in the head and neck and arm regions, the recipient vessels varied. The mean patient age was 37.7 years, and ten of 11 patients were male. Etiologies of defect were automobile accidents in six cases, neoplasm in three, and gunshot wound and electrical injury in one patient each. Mean ischemia time was 113 +/- 15 min. Mean length of AVF was 27.3 +/- 2.1 cm. All flaps survived. AVF was a useful technique in the current study. Several maneuvers were undertaken to minimize the risk of thrombosis. All patients were given aspirin prior to AVF creation. Patients received dextran 40 in the postanastomosis period for 5 days. Finally, every effort was made to create the AVF between large vessels, especially in the leg, to maximize blood flow.

Adolescent↗
PubMed1993

Upregulation by retinoic acid of interleukin-2-receptor mRNA in human T lymphocytes.

It was previously demonstrated that retinoic acid (RA) can enhance the functional responses of human T lymphocytes by increasing surface IL-2R alpha chain protein expression on proliferating T blasts, resulting in augmented IL-2-dependent growth. In the present study, we used IL-2-maintained lymphoblasts generated from human thymocytes to show that RA enhancement of IL-2R alpha is accompanied by an increase in steady-state levels of IL-2R alpha mRNA. This increase occurred within 1 hr after the addition of RA to the culture and was inhibited by the presence of the protein synthesis inhibitor cycloheximide. RA did not alter the stability of either IL-2R alpha on the cell surface or IL-2R alpha mRNA, suggesting regulation by RA at the level of transcription. This contention was supported by the demonstrated ability of RA to activate the IL-2R alpha promoter in a chloramphenicol acetyltransferase plasmid construct that was transfected into the blast cells. In addition to inducing IL-2R alpha expression, RA also increased the surface expression and mRNA levels of IL-2R beta, the 75-kDa component of the IL-2 receptor that mediates IL-2 signal transduction. These new findings showing regulation by RA of both IL-2R alpha and IL-2R beta suggest multiple pathways by which this retinoid can modulate functional IL-2 receptors.

Cells, Cultured↗
PubMed1993

New mouse primary retinal degeneration (rd-3).

A new mouse retinal degeneration that appears to be an excellent candidate for modeling human retinitis pigmentosa is reported. In this degeneration, called rd-3, differentiation proceeds postnatally through 2 weeks, and photoreceptor degeneration starts by 3 weeks. The rod photoreceptor loss is essentially complete by 5 weeks, whereas remnant cone cells are seen through 7 weeks. This is the only mouse homozygous retinal degeneration reported to date in which photoreceptors are initially normal. Crosses with known mouse retinal degenerations rd, Rds, nr, and pcd are negative for retinal degeneration in offspring, and linkage analysis places rd-3 on mouse chromosome 1 at 10 +/- 2.5 cM distal to Akp-1. Homology mapping suggests that the homologous human locus should be on chromosome 1q.

Age Factors↗
PubMed1993

Surgical management of recurrent carpal tunnel syndrome.

An approach to the surgical management of recurrent carpal tunnel syndrome was evaluated in 30 patients with 35 involved wrists. This includes internal neurolysis of the median nerve and early post-operative mobilization of the wrist and fingers. The preferred surgical approach is through a second, more ulnar incision. Clinical assessment of sensorimotor function was converted into a numerical score ranging from zero (normal) to 9 (anaesthesia) and 10 (atrophy, severe). The average pre-operative score was mean 6.5 and median 7. At a mean follow-up of 23.5 months, the average post-operative score was mean 1.8 and median 0, a statistically significant improvement (P < 0.001).

Adult↗
PubMed1993

Mitochondrial COII sequences and modern human origins.

The aim of this study is to measure human mitochondrial sequence variability in the relatively slowly evolving mitochondrial gene cytochrome oxidase subunit II (COII) and to estimate when the human common ancestral mitochondrial type existed. New COII gene sequences were determined for five humans (Homo sapiens), including some of the most mitochondrially divergent humans known; for two pygmy chimpanzees (Pan paniscus); and for a common chimpanzee (P. troglodytes). COII sequences were analyzed with those from another relatively slowly evolving mitochondrial region (ND4-5). From class 1 (third codon position) sequence data, a relative divergence date for the human mitochondrial ancestor is estimated as 1/27 th of the human-chimpanzee divergence time. If it is assumed that humans and chimpanzees diverged 6 Mya, this places a human mitochondrial ancestor at 222,000 years, significantly different from 1 Myr (the presumed time of an H. erectus emergence from Africa). The mean coalescent time estimated from all 1,580 sites of combined mitochondrial data, when a 6-Mya human-chimpanzee divergence is assumed, is 298,000 years, with 95% confidence interval of 129,000-536,000 years. Neither estimate is compatible with a 1-Myr-old human mitochondrial ancestor. The mitochondrial DNA sequence data from COII and ND4-5 regions therefore do not support this multiregional hypothesis for the emergence of modern humans.

Animals↗
PubMed1993

Comparison of continuous single layer polypropylene anastomosis with double layer and stapled anastomoses in elective colon resections.

The documented leak rate of the continuous single layer polypropylene (CSLP) anastomosis in elective colon resection is 0-6 per cent. It is more cost effective than stapling (S), and should be faster and easier to perform than the double-layer (DL) technique. However, there have been no reported series comparing the outcome of the CSLP anastomosis with the DL and S techniques. We reviewed the charts of 100 patients with elective colon resections. Eighty-four had data sufficient for analysis. There were 44 CSLP, 21 DL, and 19 S. The groups were comparable with respect to 12 preoperative variables. Proportionately more large-small bowel anastomoses were performed in the S group, and no patient in the S group was actively taking steroids. Clinical outcome was assessed. All leaks were clinically apparent and documented with contrast enema or laparotomy. The leak rate for the CSLP was 6.8 per cent (3/44). Two of the three patients with leaks were taking steroids. There were two leaks in the DL group (9.5%), one of which was taking steroids, and no leaks in the S group. The difference in leak rate between the three groups was not statistically significant. The average cost for CSLP at our institution is $4.00 compared with $8.00 and $35.00 for the DL and S, respectively. We conclude that the CSLP is a reasonable and safe alternative to DL and S anastomoses.

Anastomosis, Surgical↗
PubMed1992

Mechanistic studies on the human matrix metalloproteinase stromelysin.

To probe the mechanism of stromelysin (SLN)-catalyzed peptide hydrolysis, we determined the pH dependence of kc/Km and solvent deuterium isotope effects on kc and kc/Km. pH dependencies of kc/Km were determined for the SLN-catalyzed hydrolysis of three peptides: Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Nle-NH2,Arg-Pro-Ala-Pro-Gln-Gln- Phe-Phe - Gly-Leu-NleNH2, and N-acetyl-Arg-Pro-Ala-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Nle-NH2 (cleavage at Gln-Phe bond). The pH dependencies are all bell-shaped with shoulders that extend from pH 7.5 to 8.5. The existence of a shoulder indicates that the reaction mechanism involves at least two routes to products. These curves are governed by three proton ionizations with pKa values of 5.4, 6.1, and 9.5. The solvent isotope effect measurements provided the following values: D(kc/Km) = 0.80 +/- 0.05 and D(kc) = 1.58 +/- 0.05. That D(kc/Km) and D(kc) are different suggests that the rate-limiting transition states for the processes governed by kc/Km and kc cannot be the same. We use these results, together with analogy to thermolysin catalysis, to develop a mechanism for SLN catalysis.

Amino Acid Sequence↗
PubMed1992

Prefabrication of free flaps using the omentum in rats.

The omentum used as a vascular carrier is a new experimental model for prefabrication of free flaps in the rat. A 2.5 x 4 cm patch of omentum with gastroepiploic vessels and its rich vascular arcades was transferred under a bipedicled 2.5 x 6 cm right abdominal panniculocutaneous flap. At subsequent time intervals (postoperative days 0, 3, 5, 7, and 14), the skin pedicles were divided and the skin flap was raised as a composite island flap vascularized only by the underlying omental patch. The composite flap was then sutured back in place. Prefabricated flaps examined postoperatively demonstrated a dye fluorescence index (DFI) of 4.60% +/- 2.82% and 1.67% +/- 4.08% flap survival (FS) in the day 0 group; in the day 3 group, 9.83% +/- 1.47% of DFI and 15.00% +/- 10.35% of FS; in the day 5 group, 28.39% +/- 5.25% of DFI and 86.0% +/- 12.74% of FS (P less than 0.05); in the day 7 group, 38.19% +/- 7.52% of DFI and 98.13% +/- 3.72% of FS (P less than 0.05); and, in the day 14 group, 49.55% +/- 6.70% of DFI and 100% of FS (P less than 0.05). India-ink injection and histologic examination confirmed revascularization of the overlying skin by day 5.

Animals↗
PubMed1992

Epidemiology and microbiology of diarrhoea in young Aboriginal children in the Kimberley region of Western Australia.

Infectious diarrhoea is common in young Australian Aborigines and is one of the main causes for their unsatisfactory health standards with consequent widespread failure to thrive and undernutrition. Most published reports relate to patients in hospital or to hospital admission statistics and give little indication of the extent or severity of diarrhoeal disease in children in Aboriginal communities. The present investigation involved more than 100 Aboriginal children up to 5 years of age living in remote communities in the tropical north of Western Australia who were studied prospectively over a 12-month period.

Bacterial Infections↗
PubMed1992

The effect of tissue expansion on dermal fibroblast contraction.

Tissue expansion alters the function of skin cells. We studied the effects of expansion on the contractile function of dermal fibroblasts using an in vitro model, the fibroblast-populated collagen lattice (FPCL). Spherical expanders were placed dorsally in 30 Sprague-Dawley rats; one-half were serially inflated. One, 2, and 4 weeks later, 5 rats from each group were killed. Fibroblasts were cultured from dermis overlying the expanders and mixed with collagen, medium, and serum in petri dishes to form FPCL. Fibroblasts from 5 rats that had not undergone surgery were cultured to make control FPCL. Contraction was assessed by measuring the areas of the FPCL. At 48 hours, FPCL containing expanded fibroblasts had contracted significantly less than those containing unexpanded or control fibroblasts. Four weeks of expansion resulted in less contraction than 1 or 2 weeks. Tissue expansion inhibits the in vitro contractile function of dermal fibroblasts in the rat in a time-related fashion.

Animals↗