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Biomedical subjects

M C Cullen

Publications and source records attributed to M C Cullen.

8 recordsLinked to original sources
PubMed2004

Characterization of nutrient-induced dispersion in Pseudomonas aeruginosa PAO1 biofilm.

The processes associated with early events in biofilm formation have become a major research focus over the past several years. Events associated with dispersion of cells from late stage biofilms have, however, received little attention. We demonstrate here that dispersal of Pseudomonas aeruginosa PAO1 from biofilms is inducible by a sudden increase in carbon substrate availability. Most efficient at inducing dispersal were sudden increases in availability of succinate > glutamate > glucose that led to approximately 80% reductions in surface-associated biofilm biomass. Nutrient-induced biofilm dispersion was associated with increased expression of flagella (fliC) and correspondingly decreased expression of pilus (pilA) genes in dispersed cells. Changes in gene expression associated with dispersion of P. aeruginosa biofilms were studied by using DNA microarray technology. Results corroborated proteomic data that showed gene expression to be markedly different between biofilms and newly dispersed cells. Gene families that were upregulated in dispersed cells included those for flagellar and ribosomal proteins, kinases, and phage PF1. Within the biofilm, genes encoding a number of denitrification pathways and pilus biosynthesis were also upregulated. Interestingly, nutrient-induced dispersion was associated with an increase in the number of Ser/Thr-phosphorylated proteins within the newly dispersed cells, and inhibition of dephosphorylation reduced the extent of nutrient-induced dispersion. This study is the first to demonstrate that dispersal of P. aeruginosa from biofilms can be induced by the addition of simple carbon sources. This study is also the first to demonstrate that dispersal of P. aeruginosa correlates with a specific dispersal phenotype.

Bacterial Proteins↗
PubMed1998

Physical and arthroscopic examination techniques of the patellofemoral joint.

A systematic approach to the clinical history, physical, and arthroscopic examination of patellofemoral disorders will lead to improved diagnostic accuracy and clinical treatment success. We review important aspects of physical and arthroscopic examination of patellofemoral disorders Basic and advanced physical examination techniques are presented, and their clinical significance is reviewed. Arthroscopic examination of the patellofemoral joint is used as an adjunct to physical examination to evaluate chondral lesions of the patella and femoral sulcus and to visualize patella tracking. Techniques to assess patellar tracking and the integrity of patellar restraints and to grade chondral lesions are outlined. Utilization of these techniques will improve clinical studies on the treatment of patellofemoral disorders.

Arthroscopy↗
PubMed1996

Open fracture of the tibia in children.

The records of eighty-three children who had had an open fracture of the tibial metaphysis or diaphysis between January 1983 and July, 1993 were studied retrospectively. The average duration of follow-up was fourteen months (range, two to seventy-five months). There were twenty-four grade-I, forty grade-II, thirteen grade-IIIA, six grade-IIIB, and no grade-IIIC fractures, according to the classification scheme of Gustilo et al. Sixty patients (72 per cent) had sustained the fracture when they were struck by an automobile, and forty-eight patients (58 per cent) had other associated major injuries. All fractures were treated with irrigation and débridement, and antibiotics were administered parenterally for a minimum of forty-eight hours. Thirty-two patients were managed with immobilization in a cast only; forty, with transcutaneous fixation with an average of two Steinmann pins followed by immobilization in a cast; nine, with external fixation; one, with open reduction and internal fixation with two screws and two pins; and one, with delayed intramedullary nailing. Fifty-seven wounds were closed primarily (forty-four, over a Penrose drain, and thirteen, without a drain), ten were treated with delayed closure, four were allowed to heal by secondary intention, seven were covered with a soft-tissue flap, and five were treated with skin-grafting (a split-thickness skin graft was used for four, and a split-thickness and a full-thickness skin graft were used for one). The average time to union was fifteen weeks (range, five to sixty-one weeks), with the fracture healing by sixteen weeks in sixty-four patients (77 per cent). Eighteen patients (22 per cent) had delayed union, and only one patient (1 per cent) had non-union. Secondary procedures were necessary to achieve union in only two patients. Two patients had a superficial wound infection, and no patient had osteomyelitis. One patient, who had been managed with external fixation, had a pin-track infection; none of the patients who had had transcutaneous fixation had a pin-track infection. Two patients had a compartment syndrome, and two patients had a transient stretch injury of a nerve (the peroneal nerve in one and the sciatic nerve in the other). Four fractures healed with an angulatory deformity of more than 10 degrees in any plane. Five patients had overgrowth of the limb of one centimeter or more. Physeal arrest did not occur in any patient. We concluded that treatment of unstable open fractures of the tibia in children with débridement and transcutaneous fixation followed by immobilization in a cast leads to good anatomical and functional results. We prefer this technique to external fixation, which is associated with several potential complications. Loose closure of a clean open wound over a Penrose drain is effective and can be safely utilized in selected children.

Adolescent↗
PubMed1995

The management of severe avascular necrosis following slipped capital femoral epiphysis by transtrochanteric rotational osteotomy. Results of successful treatment in two cases with longterm follow-up.

We present two cases of unstable slipped capital femoral epiphysis complicated by avascular necrosis that were successfully treated with transtrochanteric anterior rotational osteotomy. These two cases both had severe avascular necrosis and were felt to be unsalvageable. We recommend this surgical technique as a viable alternative to other forms of treatment in this selected patient population.

Child↗
PubMed1994

Pesticide bioaccumulation in cattle.

A simple partition model was developed to evaluate the bioaccumulation of chlorinated hydrocarbon pesticides (dieldrin and heptachlor) in the soil-pasture-grazing animal system. Biomagnification factors (BFL) calculated on a lipid basis ranged from 0.115 to 0.175, but could not be directly compared with other values from the literature because of different methods of calculation. The partition model predicted values of somewhat less than unity, indicating that it does not fully account for pesticide pathways and mechanisms. However, the lack of variation of these values from two compounds indicates a lack of dependence on the octanol/water coefficient which is in accord with the model. The results suggest partitioning between food in the stomach and body tissues is a major bioaccumulation process but other major processes are also involved.

Adipose Tissue↗
PubMed1993

Polygraph lie detection on real events in a laboratory setting.

This laboratory study dealt with real-life intense emotional events. Subjects generated embarrassing stories from their experience, then submitted to polygraph testing and, by lying, denied their stories and, by telling the truth, denied a randomly assigned story. Money was given as an incentive to be judged innocent on each story. An interrogator, blind to the stories, used Control Question Tests and found subjects more deceptive when lying than when truthful. Stories interacted with order such that lying on the second story was more easily detected than lying on the first. Embarrassing stories provide an alternative to the use of mock crimes to study lie detection in the laboratory.

Adult↗
PubMedDate not supplied

Complications of intramedullary fixation of pediatric forearm fractures.

A retrospective review of 20 children with forearm fractures treated with intramedullary fixation is presented. Indications for surgery included fracture malreduction, open fracture, polytrauma, unstable fracture pattern, and compartment syndrome. Both radius and ulna were fractured in patients. Intramedullary fixation of both bones was performed in eight cases, ulna alone in nine, and isolated radius in three. A limited open approach to one or both bones was necessary for insertion of the intramedullary rod in 15 of 20 cases, including the eight open fractures. Eighteen complications occurred in 10 of 20 patients, including hardware migration, infection, loss of reduction, reoperation, nerve injury, significant decreased range of motion, synostosis, muscle entrapment, and delayed union. Despite the complications, 17 patients had excellent and two had good outcomes. Although excellent clinical results can be expected with intramedullary fixation, complications related to the surgical technique can be expected.

Adolescent↗