Spine loading characteristics of patients with low back pain compared with asymptomatic individuals

STUDY DESIGN

Patients with low back pain and asymptomatic individuals were evaluated while performing controlled and free-dynamic lifting tasks in a laboratory setting.

OBJECTIVE

To evaluate how low back pain influences spine loading during lifting tasks.

SUMMARY OF BACKGROUND DATA

An important, yet unresolved, issue associated with low back pain is whether patients with low back pain experience spine loading that differs from that of individuals who are asymptomatic for low back pain. This is important to understand because excessive spine loading is suspected of accelerating disc degeneration in those whose spines are damaged already.

METHODS

In this study, 22 patients with low back pain and 22 asymptomatic individuals performed controlled and free-dynamic exertions. Trunk muscle activity, trunk kinematics, and trunk kinetics were used to evaluate three- dimensional spine loading using an electromyography- assisted model in conjunction with a new electromyographic calibration procedure.

RESULTS

Patients with low back pain experienced 26% greater spine compression and 75% greater lateral shear (normalized to moment) than the asymptomatic group during the controlled exertions. The increased spine loading resulted from muscle coactivation. When permitted to move freely, the patients with low back pain compensated kinematically in an attempt to minimize external moment exposure. Increased muscle coactivation and greater body mass resulted in significantly increased absolute spine loading for the patients with low back pain, especially when lifting from low vertical heights.

CONCLUSIONS

The findings suggest a significant mechanical spine loading cost is associated with low back pain resulting from trunk muscle coactivation. This loading is further exacerbated by the increases in body weight that often accompany low back pain. Patient weight control and proper workplace design can minimize the additional spine loading associated with low back pain.

Disruption of PPT1 or PPT2 causes neuronal ceroid lipofuscinosis in knockout mice

PPT1 and PPT2 encode two lysosomal thioesterases that catalyze the hydrolysis of long chain fatty acyl CoAs. In addition to this function, PPT1 (palmitoyl-protein thioesterase 1) hydrolyzes fatty acids from modified cysteine residues in proteins that are undergoing degradation in the lysosome. PPT1 deficiency in humans causes a neurodegenerative disorder, infantile neuronal ceroid lipofuscinosis (also known as infantile Batten disease). In the current work, we engineered disruptions in the PPT1 and PPT2 genes to create "knockout" mice that were deficient in either enzyme. Both lines of mice were viable and fertile. However, both lines developed spasticity (a "clasping" phenotype) at a median age of 21 wk and 29 wk, respectively. Motor abnormalities progressed in the PPT1 knockout mice, leading to death by 10 mo of age. In contrast, the majority of PPT2 mice were alive at 12 mo. Myoclonic jerking and seizures were prominent in the PPT1 mice. Autofluorescent storage material was striking throughout the brains of both strains of mice. Neuronal loss and apoptosis were particularly prominent in PPT1-deficient brains. These studies provide a mouse model for infantile neuronal ceroid lipofuscinosis and further suggest that PPT2 serves a role in the brain that is not carried out by PPT1.

HIV gp120 V(1)/V(2) and C(2)-V(3) domains glycoprotein compatibility is required for viral replication

The envelope gene, especially the V(3) region, of HIV-1 has been shown to be a principal determinant of cell tropism, replication and cytopathogenicity of the virus. In addition, the V(1)/V(2) region of the envelope gene has been found to be an important factor in cell tropism. We examined the compatibility between the V(1)/V(2) and C(2)-V(3) domains of HIV-1 gp120 in different combinations on viral replication by using envelope recombinants between ME1 and ME46, two infectious molecular clones with diverse biologic activity longitudinally isolated from one seropositive subject. Our data demonstrate that a proper interaction between the regions of V(1)/V(2)and C(2) is essential for viral infection and hence replication. Sequence analysis and subsequent site directed mutagenesis study indicate that the pattern of potential envelope N-glycosylation in the V(1)/V(2) and C(2)-V(3) regions may be the determining factor in such interaction between these two regions. It is possible that improper N-glycosylation sites while not affecting virus assembly, can influence through steric hindrance the conformational change of the V(3) region that is required for the co-receptor attachment and hence the viral infectivity.

Human immunodeficiency virus type 1 env sequences from Calcutta in eastern India: identification of features that distinguish subtype C sequences in India from other subtype C sequences

India is experiencing a rapid spread of human immunodeficiency virus type 1 (HIV-1), primarily through heterosexual transmission of subtype C viruses. To delineate the molecular features of HIV-1 circulating in India, we sequenced the V3-V4 region of viral env from 21 individuals attending an HIV clinic in Calcutta, the most populous city in the eastern part of the country, and analyzed these and the other Indian sequences in the HIV database. Twenty individuals were infected with viruses having a subtype C env, and one had viruses with a subtype A env. Analyses of 192 subtype C sequences that included one sequence for each subject from this study and from the HIV database revealed that almost all sequences from India, along with a small number from other countries, form a phylogenetically distinct lineage within subtype C, which we designate C(IN). Overall, C(IN) lineage sequences were more closely related to each other (level of diversity, 10.2%) than to subtype C sequences from Botswana, Burundi, South Africa, Tanzania, and Zimbabwe (range, 15.3 to 20.7%). Of the three positions identified as signature amino acid substitution sites for C(IN) sequences (K340E, K350A, and G429E), 56% of the C(IN) sequences contained all three amino acids while 87% of the sequences contained at least two of these substitutions. Among the non-C(IN) sequences, all three amino acids were present in 2%, while 22% contained two or more of these amino acids. These results suggest that much of the current Indian epidemic is descended from a single introduction into the country. Identification of conserved signature amino acid positions could assist epidemiologic tracking and has implications for the development of a vaccine against subtype C HIV-1 in India.

Status of physical exercise and its association with obesity and hypertension in two urban assembly constituencies of East Delhi

In a community based study using systematic random sampling in two urban Assembly constituencies in East Delhi, 420 subjects above the age of 30 years were interviewed to find out their status regarding physical exercise. People doing regular exercise were found to be only 44.8%. The commonest reason associated for not doing/irregular physical exercise was nonavailability of time (63.3%), followed by no need felt by the respondents to exercise (23.3%). The prevalence of obesity in the group doing regular exercise was much lower than the group that was not doing regular exercise and the results were statistically significant. Though a similar association was found with hypertension also, the results were not statistically significant.

Retrieval of a dropped corneal button from a vitrectomized eye

A successful retrieval of a dropped corneal button from an aphakic vitrectomized eye during penetrating keratoplasty is reported. A 52-year-old female patient underwent penetrating keratoplasty for aphakic corneal edema in a vitrectomized eye. The donor button inadvertently dropped into the vitreous cavity and was retrieved successfully. The dropped corneal button was visualized after focusing the operating microscope on the retina. The visualization significantly improved after aspiration of the fluid from the vitrectomized eye. The donor button was picked up by McPherson's forceps and subsequently sutured to the recipient's cornea. Corneal surgeons need to be aware of this rare complication in aphakic vitrectomized eyes and its retrieval after accurate visualization.

Do you still need a biopsy to diagnose celiac disease?

Celiac disease is a common and permanent condition caused by an abnormal immune response to ingested gluten in genetically susceptible individuals. Its proper diagnosis is very important even in patients presenting with mild symptoms because severe and debilitating complications may occur in celiac patients not following a strict gluten-free diet. In the past several years, important progress has been made not only in our understanding of the pathogenesis of this condition but also in the availability of tools to screen it. Antigliadin antibodies, once largely used for this purpose, have been basically replaced by the more costly but far more accurate antiendomysium antibodies. More recently, the enzyme-linked immunosorbent assay (ELISA), which measures the antibodies directed against the autoantigen responsible for the disease (tissue transglutaminase), has also been developed and tested as a screening tool. Currently, however, the poor positive predictive value of this test does not allow practitioners to diagnose celiac disease without the duodenal biopsy showing the typical morphologic changes.

6-mercaptopurine metabolite levels in children with inflammatory bowel disease

OBJECTIVES

Some authors suggest that efficacy of 6-mercaptopurine (6-MP) in patients with inflammatory bowel disease correlates with circulating 6-thioguanine (6-TG) levels more than 235 pmol/8 x 10(8) red blood cells. The authors evaluated the relation between 6-MP metabolite levels and disease activity in children and adolescents with inflammatory bowel disease.

METHODS

Clinical status and hematologic and hepatic parameters were determined in 101 children with inflammatory bowel disease from a single center and compared with 6-MP metabolite levels.

RESULTS

There was a trend for higher 6-TG levels among patients in remission than among those with active disease (217 vs. 173); however the difference was not statistically significant ( P = 0.09). The likelihood of therapeutic response did not increase significantly at 6-TG levels greater than 235 pmol/8 x 10(8) red blood cells (odds ratio 1.7; P = 0.1). In the current study, 58% of patients in remission had 6-TG levels less than 235. However, serial measurements of 6-MP metabolite levels in 50 patients with active disease showed that increasing 6-TG levels correlated significantly with disease remission in patients followed up longitudinally ( P = 0.04). Leukopenia was significantly associated with high 6-TG levels ( P = 0.03) but not with clinical response ( P = 0.2).

CONCLUSIONS

These data suggest that the target range of 6-TG levels previously described by others did not apply to 58% of the pediatric patients with IBD in remission. However, serial monitoring of 6-MP metabolite levels in individual patients with active disease should allow dose escalation and induction of remission while minimizing the risk of toxicity.

Risk factors for chronic rejection after pediatric liver transplantation

BACKGROUND

Chronic rejection is a major cause of graft failure and a frequent reason for retransplantation after pediatric liver transplantation. Identification of risk factors for chronic rejection in pediatric transplant recipients is vital to understanding the pathogenesis of chronic rejection and may help prevent further graft loss.

METHODS

The study population consisted of 285 children with 385 liver transplants performed at University of Chicago between 1991 and 1999. Logistic regression analysis was used to evaluate risk factors for chronic rejection, including age, sex, race, type of graft (living related vs. cadaveric), native liver disease, acute rejection episodes, cytomegalovirus (CMV) infection, and posttransplant lymphoproliferative disease (PTLD).

RESULTS

The chronic rejection rate was significantly lower in recipients of living-related grafts than in recipients of cadaveric grafts (4% vs. 16%, P=0.001). African-American recipients had a significantly higher rate of chronic rejection than did Caucasian recipients (26% vs. 8%, P<0.001). Numbers of acute rejection episodes, transplantation for autoimmune disease, occurrence of PTLD, and CMV infection were also significant risk factors for chronic rejection. However, recipient age, gender, donor-recipient gender mismatch, and donor-recipient ethnicity mismatch were not associated with higher incidence of chronic rejection

CONCLUSION

We have identified a number of risk factors for chronic rejection in a large group of pediatric liver allograft recipients. We believe that donor-recipient matching for gender or race is not likely to reduce the incidence of chronic rejection. The elucidation of the mechanisms by which living-related liver transplantation affords protection against chronic rejection may provide insight into the immunogenetics of chronic rejection and help prevent further graft loss.

Enhanced expression of the recombinant lethal factor of Bacillus anthracis by Fed-Batch culture

High cell density cultivation has been one of the most effective ways to increase cell as well as the product yields. The structural gene for the 90-kDa lethal factor (LF) isolated from Bacillus anthracis was expressed as fusion protein with 6x histidine residues under the transcriptional regulation of the T5 promoter in Escherichia coli. Various strategies were tried to scale up the expression of the recombinant lethal factor by bioprocess optimization using fed batch culture technique in a 14 litre fermentor. The media, a defined mixture of salts, trace elements, vitamins, etc. along with a specified carbon source was used for the growth. The pH of the media was maintained at 6.8 while the temperature was changed from 37 to 28 degrees C during the cultivation. During the growth and induction phases, the DO was maintained above 20% by automatic control of agitation. The specific growth rate was controlled by utilizing an exponential feeding profile determined from mass balance equations. As a result of control of specific growth rate at two different levels, there was about twenty five fold increase in biomass compared to the biomass in the shake flask. E. coli cells yielded a soluble cytosolic protein with an apparent molecular mass of 90 kDa. The protein was purified to homogeneity using metal chelate affinity chromatography, followed by anion exchange on FPLC using Mono-Q column. In solution, trypsin cleaved protective antigen bound to native and recombinant LF with comparable affinity. The recombinant LF resembled the LF purified from B. anthracis in the macrophage lysis assay, using a murine macrophage cell line J774A.1 sensitive to anthrax toxin. It was possible to achieve a yield of 50 mg of the purified protein from 1 litre culture broth.

Effect of pH on stability of anthrax lethal factor: correlation between denaturation and activity

Anthrax is caused by Gram positive bacterium Bacillus anthracis. Pathogenesis is result of production of three protein components, protective antigen (PA), lethal factor (LF), and edema factor (EF). PA in combination with LF (lethal toxin) is lethal to animals, while PA in combination with EF (edema toxin), causes edema. PA, LF, and EF are very thermolabile. Differential scanning calorimetry (DSC) was used to unravel the energetics of LF denaturation as a function of pH ranging from 7.8 to 5.5. Transition temperature (T(m)) of LF was found to be approximately equal to 42 degrees C and onset of denaturation occurs at approximately equal to 30 degrees C. The ratio of calorimetric to van't Hoff's enthalpy was nearly equal to unity at pH 7.0, indicative of presence of single structural domain in LF at pH 7.0, unlike PA which has been structurally observed to consist of 4 domains. It was found by cytotoxicity studies using J774A.1 macrophage like cells that LF was most stable at pH approximately 6.5. This paper reports for the first time the denaturation of LF at different pH values at 37 degrees C and tries to establish a correlation between denaturation and loss of LF activity at different pH values.

A comparison of the effects of lamotrigine on neuroma-induced action potential firing and normal behaviour in rat: implications for establishing a pre-clinical 'therapeutic index'

The effects of lamotrigine on rat neuroma and behavioural paradigms were evaluated to determine a pre-clinical therapeutic index. Lamotrigine blocked neuroma-induced burst pattern firing at a free plasma concentration of 13.7+/-1.7 microM (n=5). Oral dosing of lamotrigine (50-200 mg/kg) had no significant effects on behaviour but measurements of plasma concentrations of free drug showed non-linear oral absorption and lower than predicted drug levels (5-27 microM). Given intravenously (10-100 mg/kg), lamotrigine did affect behaviour at a free plasma concentration of 42.0 microM (n=2). By comparing free plasma concentrations, a therapeutic index of 3 was calculated, which is lower than published data based on comparing oral doses. We propose that a therapeutic index should only be derived with reference to plasma drug concentrations to prevent non-linear or incomplete drug absorption from confounding accurate estimation.

Hematological observations as diagnostic markers in dengue hemorrhagic fever--a reappraisal

OBJECTIVE

To determine the utility of certain clinical and hematological parameters as diagnostic markers of dengue hemorrhagic fever (DHF), namely, (i) tourniquet test, (ii) association of bleeding manifestations with the platelet count, and (iii) "cut off" value of hematocrit diagnostic of DHF in Indian population.

DESIGN

Prospective study.

SETTING

Tertiary care hospital.

SUBJECT

304 children of DHF presenting between September 1996 to December 1996.

RESULTS

The tourniquet test had a low sensitivity and was positive only in 61/239 (25.5%) cases. There was no statistical difference in the incidence of bleeding manifestations between thrombocytopenic and non-thrombocytopenic individuals highlighting poor association of thrombocytopenia with bleeding manifestations. A "cut off" hematocrit value of 36.3% diagnostic of DHF was estimated by discriminant analysis in Indian population.

CONCLUSION

The study highlights tourniquet test as a less sensitive diagnostic marker of DHF, poor association of thrombocytopenia with bleeding manifestations and also defines the hematocrit value diagnostic of DHF in Indian population.