COMPARATIVE STUDY OF BONE HEALING FOLLOWING BONE CUTS USING SURGICAL BURS AND MICROSAWS

Bone cuts on the tibia of 6 healthy dogs were studied using surgical burs and microsaws arranged in two groups by random selection to assess the speed of cutting, precision and bone healing. Bone cuts in Group A were made with surgical burs of 1.6 mm diameter using micromotor at 40,000 revolutions per minute (RPM) whereas in Group B they were created using Stryker microsaws of 0.75 mm width at the speed of 40,000 RPM. In each group, the dogs were sacrificed at the end of 8, 12 and 16 weeks and a section of the tibia containing the fracture site was removed to assess healing histopathologically. Based on clinical, radiological and histopathological examination, the results of this study indicate that microsaws have their best use in osteotomy procedures in terms of precision and thermal injury to bone whereas ostectomy procedures are more convenient with surgical burs.KEYWORDS: Bone cuts, Bone healing, Microsaws, Surgical burs     

Prenatal growth restriction,retinal dystrophy,diabetes insipidus and white matter disease: expanding the spectrum of PRPS1-related disorders

PRPS1 codes for the enzyme phosphoribosyl pyrophosphate synthetase-1 (PRS-1). The spectrum of PRPS1-related disorders associated with reduced activity includes Arts syndrome, Charcot–Marie–Tooth disease-5 (CMTX5) and X-linked non-syndromic sensorineural deafness (DFN2). We describe a novel phenotype associated with decreased PRS-1 function in two affected male siblings. Using whole exome and Sanger sequencing techniques, we identified a novel missense mutation in PRPS1. The clinical phenotype in our patients is characterized by high prenatal maternal α-fetoprotein, intrauterine growth restriction, dysmorphic facial features, severe intellectual disability and spastic quadraparesis. Additional phenotypic features include macular coloboma-like lesions with retinal dystrophy, severe short stature and diabetes insipidus. Exome sequencing of the two affected male siblings identified a shared putative pathogenic mutation c.586C>T p.(Arg196Trp) in the PRPS1 gene that was maternally inherited. Follow-up testing showed normal levels of hypoxanthine in urine samples and uric acid levels in blood serum. The PRS activity was significantly reduced in erythrocytes of the two patients. Nucleotide analysis in erythrocytes revealed abnormally low guanosine triphosphate and guanosine diphosphate. This presentation is the most severe form of PRPS1-deficiency syndrome described to date and expands the spectrum of PRPS1-related disorders.     

How large is the lung recruitability in early acute respiratory distress syndrome: a prospective case series of patients monitored by computed tomography

Introduction  

The benefits of higher positive end expiratory pressure (PEEP) in patients with acute respiratory distress syndrome (ARDS) have been modest, but few studies have fully tested the "open-lung hypothesis". This hypothesis states that most of the collapsed lung tissue observed in ARDS can be reversed at an acceptable clinical cost, potentially resulting in better lung protection, but requiring more intensive maneuvers. The short-/middle-term efficacy of a maximum recruitment strategy (MRS) was recently described in a small physiological study. The present study extends those results, describing a case-series of non-selected patients with early, severe ARDS submitted to MRS and followed until hospital discharge or death.     

Effect of sertraline hydrochloride on dialysis hypotension

Hemodialysis hypotension (HH) is a very common disorder and has a multifactorial etiology. Autonomic dysfunction occurs in up to 50% of patients with end-stage renal disease (ESRD) and plays a key role in HH in some patients. Sertraline hydrochloride, a central nervous system serotonin reuptake inhibitor, has been shown to be an effective treatment of hypotension caused by autonomic dysfunction in disorders such as neurocardiogenic syncope and idiopathic orthostatic hypotension. This study sought to determine whether sertraline was effective in ameliorating HH. A retrospective chart analysis was performed that included nine consecutive patients (aged > or = 54 years, time on hemodialysis > or = 2.2 years) placed on sertraline (50 to 100 mg/d) for depression who also had HH (defined as prehemodialysis systolic blood pressure [SBP] < or = 100 mm Hg, > or = 40 mm Hg decrease in SBP during hemodialysis, SBP <90 mm Hg, any diastolic blood pressure <40 mm Hg, or a decrease in blood pressure-causing symptoms) before treatment with sertraline. The data from a 6-week pre-sertraline period were compared with the data from a 6-week sertraline period (defined as 6 weeks after drug begun). Blood pressure medications were unchanged during the trial period of sertraline. However, nadir mean arterial pressure recorded during a given dialysis session in the pre-sertraline period (55+/-4 mm Hg) was significantly lower than that recorded in the sertraline period (68+/-5 mm Hg; P < 0.05). In addition, the number of hypotensive episodes (same definition as HH) per dialysis session during the sertraline period was significantly lower than that during the pre-sertraline period (mean, 0.6+/-0.2 episodes per session v 1.4+/-0.3 episodes per session; P < 0.005). The number of therapeutic interventions required for hypotension during the sertraline period was also significantly less than that during the pre-sertraline period (mean, 1.7+/-0.8 interventions v 11.0+/-3.0 interventions; P < 0.005). The urea reduction ratio (62.7%+/-4.7% v 63.1%+/-9.3%; P = NS) and hematocrit (28.9%+/-0.8% v 29.5%+/-1.0%; P = NS) did not change significantly. It is concluded that the short-term (6 weeks) use of sertraline hydrochloride reduces HH in some patients with ESRD. A possible mechanism for this effect is sertraline-induced attenuation of the paradoxical sympathetic withdrawal that may underlie HH in some patients with ESRD.     

Increased HbF in sickle cell anemia is determined by a factor linked to the beta S gene from one parent

Members of 7 large families, containing 20 patients with sickle cell anemia (SS) characterized by high levels of fetal hemoglobin (HbF), were studied using immunofluorescence to count F cells and a radioimmunoassay to measure small amounts of HbF. In five of these families, one of the sickle cell trait (AS) parents had a much higher HbF and F-cell count than the other; in one family, both parents had a marked increase in HbF and F cells; in the remaining family, HbF and F cells were at borderline values in both parents. Seven of 14 AS siblings, but only 1 of 8 normal hemoglobin (AA) siblings, also had HbF and F-cell counts above the "normal" range. It seems that a factor for increased F cells, linked to the beta S gene of one parent, is segregating in these families and is responsible for the greatly increased HbF and F cells in the SS subjects. HbF per F cell in AS parents and siblings was the same as that of normal AA subjects, whereas in the SS offspring it was greatly increased, suggesting that it was the result of marrow hyperplasia associated with their hemolytic anemia. The similarity of this "increased F-cell gene" to heterocellular hereditary persistence of fetal hemoglobin (HPFH). Swiss type, is discussed, and it is suggested that it may control the persistent synthesis of HbF in sickle cell anemia by its presence in early infancy.     

A murine model for the switch from fetal to adult hemoglobin during ontogeny

In murine erythroleukemia cells, the minor/major hemoglobin (Hb) ratio depends on the cell line and the inducing agent. To determine whether mouse minor hemoglobin is a "fetal" hemoglobin in vivo, globin chain composition and synthesis rates were determined in DBA/2 mice of various ages ranging from 14-day embryos to > 6-mo adults. Globin chains were separated by electrophoresis on polyacrylamide gels containing urea and Triton X-100. This method separates the embryonic (x,y,z) and the adult (alpha, beta ma, beta mi) globin chains. Fourteen day embryos had only 5%-10% adult globins but approximately 30% of the adult beta chains were beta mi. The % beta mi decreased with age and reached 20% in adult mice. Biosynthetic studies led to more pronounced differences: beta mi synthesis was 45% of total beta chain production in 14-day embryos and declined to 22% in adults. Thus beta minor/total beta globin synthesis declines during mouse ontogeny. This resembles qualitatively the human switch from fetal to adult hemoglobin and provides a murine model for studies of hemoglobin regulation.     

Activated protein C resistance as an additional risk factor for thrombosis in protein C-deficient families

Heterozygous protein C deficiency is associated with an increased risk for thrombosis. This association is restricted to a minority of protein C-deficient families, which have been defined as clinically dominant protein C-deficient. In contrast, in the clinically recessive protein C- deficient families, only the homozygous family members are (severely) affected. One possible explanation for this difference in thrombotic risk between families may be the presence of a second hereditary risk factor. A good candidate for this second risk factor is the recently identified resistance to activated protein C (APC). APC resistance, which is associated with a mutation in the FV gene (FV Leiden), is a common and strong risk factor for thrombosis. We show here that the prevalence of the FV Leiden mutation is high among symptomatic protein C-deficient probands (19%). In 6 clinically dominant protein C- deficient families, the segregation of the FV Leiden mutation and the protein C gene mutation was studied. A thrombotic episode had been experienced by 73% of the family members having both the protein C gene mutation and the FV Leiden mutation. In contrast, respectively, 31% and 13% of the family members having either the protein C gene mutation or the FV Leiden mutation had experienced a thrombotic episode. Moreover, the result of a two locus linkage analysis support the assumption that the FV gene and the protein C gene are the two trait loci responsible for the thrombophilia. These results indicate that carriers of both gene defects have an increased risk for thrombosis compared with related carriers of the single defect.