Attenuation of virulence by disruption of the Mycobacterium tuberculosis erp gene

The virulence of the mycobacteria that cause tuberculosis depends on their ability to multiply in mammalian hosts. Disruption of the bacterial erp gene, which encodes the exported repetitive protein, impaired multiplication of M. tuberculosis and M. bovis Bacille Calmette-Guérin in cultured macrophages and mice. Reintroduction of erp into the mutants restored their ability to multiply. These results indicate that erp contributes to the virulence of M. tuberculosis.     

A review of our first 100 cases of laparoscopic nephrectomy: defining risk factors for complications

OBJECTIVE: To present the complications from our first 100 cases of laparoscopic nephrectomy, a technically demanding procedure requiring lengthy experience, and to define the risk factors. PATIENTS AND METHODS: Indications for laparoscopic nephrectomy included patients requiring nephrectomy for benign pathology and those requiring nephroureterectomy for upper tract transitional cell carcinoma confined to the upper ureter and/or renal pelvis. All patients were operated on by one surgeon (D.A.T.) via a transperitoneal route and data on diagnosis, outcome and complications collected prospectively. RESULTS: The overall complication rate was 18%, of which 3% were major and 15% minor complications. Five cases were converted to open surgery electively. Complications and conversions were associated with a history of pyonephrosis, previous renal surgery, staghorn calculi, polycystic kidney disease, and xanthogranulomatous pyelonephritis. While there was no discernible decline in the decrease in complications with experience, operative duration decreased from a mean of 204 min for the first 20 cases to 108 min for the last 20. Complications and conversions were more closely associated with diagnosis than with the surgeon's experience. CONCLUSION: Laparoscopic nephrectomy and nephroureterectomy can be undertaken for a variety of indications with reasonable complication and conversion rates. Although inflammatory conditions increase the difficulty of these procedures, we feel that patients requiring nephrectomy for benign disease should be offered a trial of laparoscopic surgery.     

Mutational analysis of Arg197 of rat surfactant protein A. His197 creates specific lipid uptake defects

In previous studies, tandem mutagenesis of Glu195 and Arg197 of surfactant protein A (SP-A) has implicated both residues as critical participants in the interaction of the molecule with alveolar type II cells and phospholipids. We substituted Ala, Lys, His, Asp, and Asn mutations for Arg to evaluate the role of a basic amino acid at position 197 in SP-A action. Unexpectedly, Ala197 retained complete activity in the SP-A functions of carbohydrate binding, type II cell binding, inhibition of surfactant secretion, lipid binding, lipid aggregation, and lipid uptake by type II cells. The results unambiguously demonstrate that Arg197 is not mechanistically essential for SP-A function. The Lys197 mutation displayed all functions of the wild type protein but exhibited a 2-fold increase in lipid uptake activity. The His197 mutation displayed all SP-A functions studied except for lipid uptake. The results obtained with the His197 mutation clearly demonstrate that lipid aggregation alone by SP-A is insufficient to promote lipid uptake by type II cells. These findings indicate that specific interactions between type II cells and SP-A are involved in the phospholipid uptake processes.     

Tendon repair by laser welding: a histologic and biomechanical comparison and suture repair with CO2 and argon lasers

BACKGROUND AND OBJECTIVE: The purpose of this study was to determine whether welding of tendinous tissue is possible with the application of thermal lasers. STUDY DESIGN MATERIALS AND METHODS: After sharp transection of a unilateral achilles tendon, 40 male outbred Spraque Dawley rats were divided equally between four treatment groups. Ten animals underwent repair using the modified Kessler suture technique. The remaining animals underwent application of laser after the tendon edges were reapproximated and held in place with a vascular clamp. CO2 and Nd:YAG lasers were applied using 25% human albumin as a solder. Fluorescein dye was added to albumin and used as solder for the Argon laser. Biomechanical and histologic testing were performed immediately and 14 days postoperatively. RESULTS: Argon and CO2 lasers successfully fused the tendon ends together. However, immediately postoperative, the resultant tissue weld was tenuous and conventional tensile strength testing was not possible. At 14 days postoperatively, all modes of tendon repair resulted in tensile failure at consistently lower levels of tension than those required for the normal uninjured tendons. The ultimate tensile strength for the suture-repaired, CO2 laser welded, and Argon laser welded tendons were 74%, 59%, and 64% of the strength of the control tendons respectively. No statistically significant difference was found in the tensile strength among the three repair groups. Histologic evaluation at 14 days revealed the greatest degree of inflammatory response in those tendons repaired with the Argon laser. Those tendons repaired with suture demonstrated the least amount of inflammatory change. CONCLUSION: Our study demonstrates that welding of a tendon is possible with the application of laser energy. However, we were unable to produce a weld sufficient to withstand significant tensile loads in the immediate postoperative period.     

Growth enhancement of Bifidobacterium lactis Bo and Lactobacillus acidophilus Ki by milk hydrolyzates

The determination of the best conditions of preparation of a (tentatively) probiotic starter culture that might be suitable for cheese making composed solely of Bifidobacterium lactis Bo and Lactobacillus acidophilus Ki is critical if a consistently reliable acid production is to be achieved, especially because bifidobacteria have stringent requirements for growth. Therefore, we determined whether B. lactis Bo and L. acidophilus Ki required or benefitted from the addition of milk hydrolyzates (brought about by proteinase or neutrase as the nitrogen source). The growth and acid production of B. lactis in milk were affected by the addition of proteinase-mediated hydrolyzate and, to a lesser extent, by neutrase-mediated hydrolyzate; a higher degree of hydrolysis of either hydrolyzate resulted in greater biomass increase and greater acid production. This result suggests that the poor growth of bifidobacteria in milk is due partially to the lack of small peptides and free amino acids. The rates of growth and acidification by B. lactis were enhanced when cocultured with L. acidophilus (1:1 inoculum ratio). Conversely, the growth rates and acid production of L. acidophilus were not positively affected by the addition of either milk hydrolyzate. Although L. acidophilus grew slowly, its proteolytic system was apparently able to generate its own nitrogen source. Nevertheless, coculture with B. lactis (1:1 inoculum ratio) led to enhanced rates of growth and acidification when compared with that of the single strain, suggesting some degree of symbiosis between the strains.     

Effects of load and tone on the mechanics of isolated human bronchial smooth muscle

Isotonic and isometric properties of nine human bronchial smooth muscles were studied under various loading and tone conditions. Freshly dissected bronchial strips were electrically stimulated successively at baseline, after precontraction with 10(-7) M methacholine (MCh), and after relaxation with 10(-5) M albuterol (Alb). Resting tension, i.e., preload determining optimal initial length (Lo) at baseline, was held constant. Compared with baseline, MCh decreased muscle length to 93 +/- 1% Lo (P < 0.001) before any electrical stimulation, whereas Alb increased it to 111 +/- 3% Lo (P < 0.01). MCh significantly decreased maximum unloaded shortening velocity (0.045 +/- 0.007 vs. 0.059 +/- 0.007 Lo/s), maximal extent of muscle shortening (8.4 +/- 1.2 vs. 13.9 +/- 2.4% Lo), and peak isometric tension (6.1 +/- 0.8 vs. 7.2 +/- 1.0 mN/mm2). Alb restored all these contractile indexes to baseline values. These findings suggest that MCh reversibly increased the number of active actomyosin cross bridges under resting conditions, limiting further muscle shortening and active tension development. After the electrically induced contraction, muscles showed a transient phase of decrease in tension below preload. This decrease in tension was unaffected by afterload levels but was significantly increased by MCh and reduced by Alb. These findings suggest that the cross bridges activated before, but not during, the electrically elicited contraction may modulate the phase of decrease in tension below preload, reflecting the active part of resting tension.