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Biomedical subjects

R A Shatford

Publications and source records attributed to R A Shatford.

9 recordsLinked to original sources
PubMed2001

The treatment of major devascularizing injuries of the upper extremity.

The most complex aspect of managing major devascularizing injuries is decision making. The decision to amputate or revascularize is not difficult in injuries that have extremely favorable or unfavorable outcomes. In less obvious cases, however, decision making can be extremely complex, and many factors influence the surgeon's decision. In borderline cases, the optimal decision may never become clear, even in hindsight, much less at the time of the initial surgery. Nor are the ramifications of these decisions trivial. The decision whether to attempt revascularization or perform a revision amputation can have a profound influence on the course of a patient's life. Despite the critical nature of these decisions, there are few firm data to guide the decision-making process in complex cases. In addition, there are a virtually infinite number of possible injury presentations, and each factor to be considered has shades and gradations of its own. Ultimately, the decision comes down to the surgeon's knowledge, experience, and ability to project the expected risk-benefit ratios of the various options and, at the same time, attempt to account for all the factors that may influence outcome. Where more than one reasonable option exists, the patient's or family's wishes can be a critical factor as well.

Amputation, Surgical↗
PubMed1999

A comparative analysis of the six-strand double-loop flexor tendon repair and three other techniques: a human cadaveric study.

The ideal zone II flexor tendon repair would be easy to perform, cause minimal scarring, and be strong enough to allow early active motion. A 6-strand loop suture technique devised by the senior author (T.M.T.) was studied in vitro. Forty flexor tendons were harvested from fresh-frozen human hands and divided into 4 groups of 10 tendons each. Each group of tendons was repaired with a specific technique: group 1, the modified Kirchmayr (modified Kessler) technique; group 2, the single-loop 2-strand technique described by Tsuge; group 3, Tsai's double-loop 4-strand modification of Tsuge's technique; and group 4, Tsai's double-loop 6-strand modification of Tsuge's technique. Gap resistance of each repair technique was recorded on a computer using a Differential Variable Reluctance Transducer (MicroStrain, Burlington, VT) and on videotape to record first gap formation, 1-mm and 2-mm gap formation, and maximum load. Statistically significant differences between groups were as follows: at first gap formation between the 2-strand and 6-strand loop suture techniques, and at maximum load between the modified Kessler and 4-strand, modified Kessler and 6-strand, 2-strand and 4-strand, and 2-strand and 6-strand loop suture techniques. The 6-strand double-loop suture technique had a higher tensile strength than the other techniques, as measured in this model at each stage in our experiment. The 6-strand double-loop suture technique simplifies flexor tendon repair. It improves the repair's strength and its resistance to gapping without increasing tendon handling or bulk. This increased repair strength allows us to pursue a more aggressive rehabilitation program.

Biomechanical Phenomena↗
PubMed1995

A technique for porcine hepatocyte harvest and description of differentiated metabolic functions in static culture.

Current bioartificial liver devices are based on the use of a large mass of hepatocytes exhibiting differentiated metabolic function. The pig has become a source of interest for the acquisition of such cells-however, harvesting a large mass of highly viable cells has met with difficulty. This study describes a technique for harvesting large quantities of hepatocytes at viabilities greater than 90% and also describes several features documenting differentiated function. Pigs, 6 to 10 kg body weight, underwent in situ two-step whole liver perfusion (ethylene glycol tetraacetic acid and collagenase) and ex vivo cell harvest. Harvests yielded an average of 19.5 billion cells with an average viability of 94.6%. Hepatocytes were then entrapped in type I collagen (3 x 10(5) cells/well) and cultured in serum-free media for 5 days. Pig hepatocytes produced stable amounts of albumin and maintained cytochrome P-450 and glucuronidation activity over 5 days, as shown by the metabolism of lidocaine and 4-methylumbelliferone. These data indicate that pig hepatocytes can be harvested with high yields and can retain viability and differentiated function over at least 5 days of culture, and therefore should prove to be an excellent source of hepatocytes for bioartificial liver devices.

Animals↗
PubMed1995

Extended liver-specific functions of porcine hepatocyte spheroids entrapped in collagen gel.

The potential use of porcine hepatocytes in a bioartificial liver device requires large quantities of viable and highly active cells. To facilitate the scaling up of the system, liver specific activities of hepatocytes should be maximized. One way of enhancing the specific activities is to cultivate hepatocytes as multicellular spheroids. Freshly isolated porcine hepatocytes form spheroids when cultivated in suspended cultures. These spheroids exhibit higher activities for a number of liver specific functions compared to hepatocytes cultivated as monolayers. However, these activities decreased in a few days in culture. Entrappment of spheroids in collagen gel sustained their metabolic activities at a stable level over 21 days. Production of albumin and urea by spheroid hepatocytes entrapped in collagen gels were 2 to 3 times higher than those by freshly isolated single cells. P-450 activity was demonstrated by metabolism of lidocaine to its main metabolite, monoethylglycinexylidide. Phase II drug metabolism was demonstrated by glucuronidation of 4-methylumbelliferone. This work shows that porcine hepatocyte spheroids entrapped in collagen maintain differentiated functions for an extended time period. Such hepatocyte spheroid entrappment system may facilitate the development of a bioartificial liver support device.

Albumins↗
PubMed1993

Staining with fluorescein diacetate correlates with hepatocyte function.

To establish the importance of fluorescein diacetate (FDA) as a viability stain for cultured hepatocytes, we hypothesized that FDA staining would correlate positively with hepatocyte viability and function. Mixtures of live and dead cells were stained with FDA and scanned by flow cytometry. A close correlation was observed between the live cell fraction and percent viability as determined by FDA staining (R2 = 0.962). Hepatocytes were also sorted into low fluorescence and high fluorescence groups. Both albumin production and lidocaine metabolism (P-450 activity) were significantly increased in the high fluorescence group compared to the low fluorescence group. An automated, fluorescence-activated assay was useful for rapid assessment of hepatocyte viability. In addition, the intensity of green fluorescence following staining with FDA correlated well with two specific measures of hepatocyte function.

Albumins↗
PubMed1992

Primary culture of rat hepatocytes entrapped in cylindrical collagen gels: an in vitro system with application to the bioartificial liver. Rat hepatocytes cultured in cylindrical collagen gels.

A static culture model employing cylindrical collagen-hepatocyte gels is reported for large scale testing of conditions relevant to the three compartment hollow fiber bioartificial liver. High density hepatocyte cultivation was achieved by cell entrapment within the collagen-hepatocyte gel. Hepatocyte viability was assessed by vital staining, gel contraction, and insulin utilization. Measures of hepatocyte-specific function included albumin synthesis, ureagenesis, lidocaine biotransformation, and cholate conjugation. Although hepatocyte viability remained stable through the seven day incubation period, hepatocyte functions were not uniformly preserved. Albumin synthesis remained stable, while representative P-450 and conjugation activities decreased with time. This static culture system will facilitate the development of a hollow fiber bioartificial liver which utilizes cylindrical collagen-hepatocyte gels.

Albumins↗
PubMed1992

Hepatocyte function in a hollow fiber bioreactor: a potential bioartificial liver.

We have developed a novel hepatocyte loaded hollow fiber bioreactor as a potential bioartificial liver. Freshly harvested rat hepatocytes were entrapped in a three-dimensional gel matrix within hollow fibers in a perfused bioreactor. Gel entrapment allowed cells to be cultured at high density while maintaining tissue-specific function. Hepatocyte function was evaluated in 10 bioreactors, each containing approximately 5 x 10(7) cells. Oxygen consumption averaged 0.32 pmole/cell/hr, albumin appearance averaged 0.60 pg/cell/hr, and lidocaine clearance (a measure of the P-450 activity) averaged 0.74 pg/cell/hr. Function persisted for the 7 days of the study. Electron microscopy at 7 days showed the distinctive ultrastructure of viable, differentiated hepatocytes: bile canaliculi, intercellular junctions, peroxisomes, abundant mitochondria, and glycogen granules. Maintenance of tissue specific function and ultrastructure suggests that this bioreactor configuration has potential as a device to support patients in liver failure, as well as to study hepatocytes in vitro.

Amino Acids↗
PubMed1992

Hepatocyte culture systems for artificial liver support: implications for critical care medicine (bioartificial liver support).

OBJECTIVE: The primary purpose of this review article is to familiarize critical care practitioners with newly developing techniques of hybrid artificial liver support. Implantable and extracorporeal hepatocyte culture systems are emphasized based on their current experimental and clinical status. DATA SOURCES: Data used to prepare this document were obtained from the authors' personal files, as well as the computerized MEDLINE database. Medical headings used include: liver, artificial organs, cell culture, growth hormones, extracellular matrix, and transplantation. Only articles published in English have been cited. STUDY SELECTION: All studies are discussed in which hepatocyte culture systems have been used to support human patients with liver failure. All studies reported the patient's condition before therapy, duration of therapy, and outcome after therapy in order to be included in this review. Since the number of clinical trials is small at this time, animal studies were used to demonstrate application of other systems in the treatment of experimentally induced liver failure. Similar selection criteria were used to select animal studies for review. All initially identified human studies met these selection criteria. DATA EXTRACTION: Independent extraction by multiple observers. DATA SYNTHESIS: Liver failure, resulting from infection, drugs, or as a part of the multiple organ failure syndrome, remains a major cause of morbidity, mortality, and resource allocation. Current therapy is limited to supportive care, along with liver transplantation. Because of these therapeutic limitations, hybrid artificial liver systems have been proposed for temporary and long-term hepatic support. Several animal studies and a small number of preliminary human studies indicate that hepatocyte culture systems are capable of supporting nearly all essential hepatic functions and may supply biologically active substances that promote regeneration and repair of the damaged liver being supported. Hybrid systems may be constructed from materials that serve as immunoprotective barriers against host defenses. CONCLUSIONS: During the past decade, important progress has been made with hybrid artificial liver support systems. Cell culture technology has progressed sufficiently so that an artificial liver, composed of metabolically active hepatocytes, may be a potential reality in the foreseeable future. Both implantable and extracorporeal artificial liver support systems have been developed to provide metabolic support during acute liver failure, or to serve as a bridge to solid organ transplantation. Implantable hepatocyte systems, however, require a prolonged period for intraperitoneal engraftment and vascularization, not typically available to patients with acute liver failure. For this reason, extracorporeal hybrid designs offer the greatest hope for on-line treatment of acute liver failure. Such systems are entering the final stages of animal testing.

Animals↗