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Biomedical subjects

J Freund

Publications and source records attributed to J Freund.

At least 19 recordsLinked to original sources
PubMed1996

Screening for osteoporosis: what is the role of heel ultrasound?

Could focused population screening detect osteoporosis earlier and improve the management of this major health care problem? Quantitative ultrasound of the calcaneus is currently being proposed as a suitable screening technique. Correlations between quantitative ultrasound of the calcaneus and dual energy x-ray absorptiometry of bone mineral density of the spine and proximal femur are not high enough to reliably predict bone mineral density at the lumbar spine or proximal femur from the ultrasound results. Some ongoing longitudinal studies suggest that quantitative ultrasound may none the less detect individuals at increased risk of fracture, but its use for mass screening for osteoporosis would be premature.

Absorptiometry, Photon↗
PubMed1996

Pilot study of the efficacy of atevirdine in the treatment of AIDS dementia complex.

OBJECTIVES: To determine the efficacy of the non-nucleoside reverse transcriptase inhibitor atevirdine in the treatment of AIDS dementia complex (ADC). DESIGN: Open label pilot study. METHODS: Ten patients with ADC (stage 1 or 2) who were intolerant to zidovudine or dideoxyinosine, or in whom the antiretrovirals had failed to prevent further decline in CD4 cell levels, were entered into the study. Atevirdine, 1800 mg daily in three divided doses, was given over a 12-week period. Patients were assessed neurologically and neuropsychologically every 4 weeks. Cerebrospinal fluid analysis was performed at entry and at weeks 4 and 12. Technetium-99 exametazine single photon emission computed tomographic cerebral perfusion scans and magnetic resonance imaging brain scans were performed at weeks 0 and 12. RESULTS: Five patients completed the 12 week protocol. Four of these five responded to atevirdine, as judged by quantified neurological and neuropsychological assessments. Atevirdine was well tolerated apart from the development of rash, anxiety, intermittent diarrhoea and fatigue. CONCLUSIONS: These preliminary results suggest that atevirdine is efficacious in the treatment of ADC. Larger blinded studies of this class of drug in the treatment of ADC are required.

AIDS Dementia Complex↗
PubMed1996

Bile acid malabsorption in HIV infected patients with chronic diarrhoea.

AIMS: To look for the presence of bile acid malabsorption in HIV infected patients with chronic diarrhoea and determine whether bile sequestering agents may have a role in palliating this common problem. METHODS: Nineteen HIV infected patients with chronic diarrhoea (duration > one month) poorly controlled on conventional treatment were investigated using the seven day retention of 75seleno-23-homocholic acid taurine (SeHCAT) as a measure of bile acid loss from the enterohepatic circulation. Patients with evidence of bile acid malabsorption were offered cholestyramine. RESULTS: Sixteen (84%) had evidence of bile acid malabsorption (< 15% retention at seven days). Ten of the 16 patients with bile acid malabsorption had terminal ileal biopsies-six had ileitis and four normal histology, suggesting that malabsorption is not always related to terminal ileitis. Thirteen patients with bile acid malabsorption have been treated with cholestyramine and 11 have reported a symptomatic response. CONCLUSIONS: Bile acid malabsorption can be demonstrated in some cases of HIV associated chronic diarrhoea and we suggest a therapeutic trial of a bile sequestering agent in patients whose symptoms are not well controlled using conventional anti-diarrhoeal agents.

Adult↗
PubMed1996

Specific cleavage sites of Nef proteins from human immunodeficiency virus types 1 and 2 for the viral proteases.

Human immunodeficiency virus type 2 (HIV-2) Nef is proteolytically cleaved by the HIV-2-encoded protease. The proteolysis is not influenced by the absence or presence of the N-terminal myristoylation. The main cleavage site is located between residues 39 and 40, suggesting a protease recognition sequence, GGEY-SQFQ. As observed previously for Nef protein from HIV-1, a large, stable core domain with an apparent molecular mass of 30 kDa is produced by the proteolytic activity. Cleavage of Nef from HIV-1 in two domains by its own protease or the protease from HIV-2 is also independent of Nef myristoylation. However, processing of HIV-1 Nef by the HIV-2 protease is less selective than that by the HIV-1 protease: the obtained core fragment is heterogeneous at its N terminus and has an additional cleavage site between amino acids 99 and 100. Preliminary experiments suggest that the full-length Nef of HIV-2 and the core domain are part of the HIV-2 particles, analogous to the situation reported recently for HIV-1.

Aspartic Acid Endopeptidases↗
PubMed1996

Abdominal fat and insulin resistance in normal and overweight women: Direct measurements reveal a strong relationship in subjects at both low and high risk of NIDDM.

Insulin resistance appears to be central to obesity, NIDDM, hyperlipidemia, and cardiovascular disease. While obese women with abdominal (android) fat distribution are more insulin resistant than those with peripheral (gynecoid) obesity, in nonobese women, the relationship between abdominal fat and insulin resistance is unknown. By measuring regional adiposity with dual-energy X-ray absorptiometry and insulin sensitivity by euglycemic-hyperinsulinemic clamp in 22 healthy women, with a mean +/- SE body BMI of 26.7 +/- 0.9 kg/m2 and differing risk factors for NIDDM, we found a strong negative relationship between central abdominal (intra-abdominal plus abdominal subcutaneous) fat and whole-body insulin sensitivity (r = -0.89, P < 0.0001) and nonoxidative glucose disposal (r = -0.77, P < 0.001), independent of total adiposity, family history of NIDDM, and past gestational diabetes. There was a large variation in insulin sensitivity, with a similar variation in central fat, even in those whose BMI was <25 kg/m2. Abdominal fat had a significantly stronger relationship with insulin sensitivity than peripheral nonabdominal fat (r2 = 0.79 vs. 0.44), and higher levels were associated with increased fasting nonesterified fatty acids, lipid oxidation, and hepatic glucose output. Because 79% of the variance in insulin sensitivity in this heterogeneous population was accounted for by central fat, abdominal adiposity appears to be a strong marker and may be a major determinant of insulin resistance in women.

Abdomen↗
PubMed1995

Complete 1H nuclear magnetic resonance assignments and structural characterization of a fusion protein of the alpha-amylase inhibitor tendamistat with the activation domain of the human immunodeficiency virus type 1 Tat protein.

Complete sequence-specific assignments of the 1H-NMR spectrum of a fusion protein of the alpha-amylase inhibitor tendamistat from Streptomyces tendae and the activation domain of Tat from human immunodeficiency virus type 1 (HIV-1) was obtained by homonuclear two-dimensional NMR methods. The protein behaves as expected for an ideal fusion protein: the flexible linker allows an almost completely decoupled motion of the subunits of the protein and the two subunits show almost no mutual interaction. In the tendamistat part, small structural distortions due to exchange of the carboxy-terminal leucine propagate mainly via the hydrogen bonds of the beta-sheet and the disulfide bond. The Tat part of the protein contains the seven cysteine residues of full-length Tat. The fusion protein was expressed in Streptomyces lividans and exported. During the export to the extracellular space disulfide bonds are created by the expressing cells, only one sulfhydryl group remains accessible for sulfhydryl reagents. Although a unique, dominant conformation with a specific disulfide bonding pattern exists, a significant conformational variation can be observed including cis-proline peptide bonds, which may indicate smaller populations with alternative disulfide bonding patterns.

Amino Acid Sequence↗
PubMed1995

Adults with growth hormone deficiency have abnormal body composition but normal energy metabolism.

We compared body composition and energy metabolism in a cross-sectional study involving 21 GH-deficient (GHD) and 29 normal adults. Fifteen subjects from each group were pair-matched for age, sex, height, and weight. Comparison of body composition by dual energy x-ray absorptiometry in the 15 pairs showed that GHD subjects had a significantly greater fat mass (23.9 +/- 1.8 vs. 19.8 +/- 2.6 kg; P = 0.02), lower bone mineral content (2.6 +/- 0.1 vs. 2.9 +/- 0.1 kg; P = 0.06), and lower fat-free soft tissue mass (FFSTM; 45.8 +/- 2.5 vs. 48.9 +/- 2.6 kg; P = 0.02). To determine which subcompartment changes were responsible for the reduced FFSTM in GH deficiency, extracellular water (ECW) was measured by 24Na dilution in 11 of the subject pairs, and body cell mass (BCM) was derived by subtracting ECW from FFSTM. The GHD subjects had lower ECW (19.4 +/- 1.0 vs. 21.0 +/- 1.0 kg; P = 0.05) and BCM (26.6 +/- 1.9 vs. 28.6 +/- 2.1 kg; P = 0.08) than their normal counterparts, with the difference approaching statistical significance. When the relationship between ECW and FFSTM was compared in the larger group of 18 GHD and 27 normal subjects, no statistically significant difference was found between the 2 regression lines, indicating that ECW and BCM were proportionately reduced in GH deficiency. Energy expenditure and fuel utilization before and after a standardized mixed meal were measured by indirect calorimetry in 12 matched pairs of GHD and normal subjects. Comparison of energy expenditure and fuel utilization showed no significant difference in fasting or postprandial energy expenditure, or carbohydrate or fat oxidation rates between the two groups. We conclude that GHD adults have an increased FM, a reduced FFSTM due to a proportionate reduction in ECW and BCM, and no detectable disturbance in energy metabolism.

Adult↗
PubMed1994

A possible regulation of negative factor (Nef) activity of human immunodeficiency virus type 1 by the viral protease.

Negative factor (Nef) protein from human immunodeficiency virus type 1 (HIV-1) is cleaved into two well-defined domains by the HIV-1-encoded protease. The cleavage site is located between Trp57 and Leu58 and is well conserved. The two domains are stable in the presence of protease for more than 48 h. The C-terminal core domain contains a well-conserved well-folded region. The cleavage releases the core domain from the myristoylated membrane anchor domain. As is the case for other HIV proteins, cleavage of Nef could be crucial for correct biological function.

Amino Acid Sequence↗
PubMed1994

Stability and proteolytic domains of Nef protein from human immunodeficiency virus (HIV) type 1.

Proteolytic experiments in conjunction with 1H-NMR spectroscopy show that the Nef (negative factor) protein from human immunodeficiency virus type 1 probably consists of two main domains, the N-terminal anchor domain at amino acid positions 2-65 and the C-terminal core domain at positions 66-206. The N-terminal domain is likely to be located at the surface of the protein, while the C-terminal domain has a compactly folded core and is stable in the absence of the anchor domain. It is conceivable that the core domain represents a functional domain of the Nef protein, activated after the removal of the membrane anchor by the human-immunodeficiency-virus protease or cellular proteases. Nef is stable at pH 5-12 and denatures at 317-322 K. The Nef protein remains in its native conformation in dimethyl-sulfoxide/water mixtures up to 35% (by vol.), and in acetonitrile/water up to 14% (by vol.). Nef refolds spontaneously after denaturation with urea or guanidinium hydrochloride. The 1H-NMR parameters and pKa values of five of the nine histidine residues and one of the seven tyrosine residues were determined and were found in four cases to be typical for residues which are not located in the interior of the protein.

Amino Acid Sequence↗
PubMed1994

Mechanisms of rapid bone loss following cardiac transplantation.

Rapid bone loss after orthoptic cardiac transplantation (OHTX) is a major problem; however, the mechanisms are poorly understood. To investigate these mechanisms we measured biochemical and hormonal indices of bone turnover serially in 25 patients (21 men, 4 women) after OHTX. Serum osteocalcin was reduced immediately post-OHTX (2.2 +/- 0.5 ng/ml) but rose significantly by 6 and 12 months (14.1 +/- 2.5 and 15.7 +/- 2.2 respectively). Bone resorption indices (urinary hydroxyproline/creatinine and calcium/creatinine ratios) were increased immediately post-OHTX but fell by 6 months. Serum testosterone was reduced in males but recovered towards normal values by 6-12 months. Regression analysis showed lumbar bone loss was predicted independently by the change in both serum osteocalcin and testosterone. The data suggest that bone loss post-OHTX is due to a combination of accelerated turnover and hypogonadism.

Absorptiometry, Photon↗
PubMed1994

Body composition and energy expenditure in acromegaly.

To investigate whether GH is a regulator of body composition and energy metabolism in adult life, we have compared body composition and resting energy expenditure (REE) in a cross-sectional study in 20 acromegalic and 20 normal subjects, pair-matched for sex, age, height, and weight. In a longitudinal study, 8 acromegalic patients were also studied before and after 12 weeks of treatment [n = 6 during octreotide (100 micrograms, 3 times/day); n = 2 after pituitary surgery], and 7 patients were studied 12 weeks after withdrawal of octreotide. REE was measured by indirect calorimetry and fat mass and fat-free soft tissue mass (FFSTM) by dual energy x-ray absorptiometry. A subgroup of 12 matched pairs of subjects and 7 treated patients had measurement of extracellular water (ECW) by 24Na dilution, which when subtracted from FFSTM provided an estimate of body cell mass (BCM). Fat mass was significantly reduced (25.4 +/- 2.2 vs. 29.7 +/- 2.7 kg; P = 0.007) and FFSTM increased (53.3 +/- 2.2 vs. 49.2 +/- 2.3 kg; P = 0.003) in acromegaly with ECW (25.6 +/- 1.6 vs. 21.1 +/- 0.9 L; P = 0.0003), but not BCM, significantly elevated. Treatment of acromegaly increased fat mass and reduced FFSTM [change (delta), -1.3 +/- 0.4 kg; P = 0.004]; the latter reflected a significant fall in ECW (delta, -2.2 +/- 0.4 L; P = 0.002), but not BCM. The opposite effect on body composition occurred after treatment withdrawal. REE was increased in acromegaly (1682 +/- 49 vs. 1540 +/- 45 Cal/24 h; P = 0.02) and significantly related to insulin-like growth factor-I (P = 0.02). REE was significantly reduced (delta, -154 +/- 17 Cal/24 h; P = 0.0001) with treatment and increased after treatment withdrawal (P = 0.003). In acromegaly, there is a reversible 1) reduction in fat mass; 2) increase in FFSTM, accounted for by an increase in ECW, but not BCM; and 3) increase in REE, which is dependent on disease activity. We conclude from these observations in acromegaly that GH is a regulator of energy metabolism and body composition.

Absorptiometry, Photon↗
PubMed1994

Platelet-derived growth factor is an autocrine growth stimulator in retinal pigmented epithelial cells.

The retinal pigmented epithelium (RPE) plays a major role in normal and exaggerated retinal wound repair; the latter can result in epiretinal membrane formation and loss of vision. The RPE forms a stable monolayer of highly differentiated cells that proliferates only during wound repair. The mechanism underlying the change to the proliferating phenotype is unknown. When grown on a plastic substratum, cultured RPE cells mimic the proliferating phenotype in situ; they escape density arrest and proliferate in serum-free medium. In this study, we have demonstrated that a platelet-derived growth factor (PDGF) autocrine loop is involved in RPE growth in serum-free medium, because: (1) RPE cells secrete PDGF into their media and express PDGF receptors; (2) the PDGF receptors on RPE cells are autophosphorylated in serum-free medium and suramin, an agent that displaces PDGF and other growth factors from their receptors, blocks the autophosphorylation; and (3) a neutralizing antibody to PDGF significantly decreases RPE growth in serum-free medium. When a linear scrape is made in an RPE monolayer, the cells migrate and proliferate to fill in the gap mimicking wound repair in situ. Cells along the edge of the scrape show increased expression of PDGF and PDGF-beta receptors, and increased staining for proliferating cell nuclear antigen. Immunohistochemistry and in situ hybridization demonstrate expression of PDGF in ganglion cells and cells of retinal blood vessels. PDGF is not detected in the outer retina or RPE in untreated eyes, but is detected in RPE participating in wound repair, either adjacent to laser burns or underlying retinal detachment. PDGF and PDGF receptors are also expressed in RPE in epiretinal membranes removed during vitreous surgery. These data suggest that PDGF is an autocrine stimulator of growth in RPE that plays a role in retinal wound repair and epiretinal membrane formation.

Animals↗
PubMed1993

Prediction of osteoporotic fractures by postural instability and bone density.

OBJECTIVE: To investigate the utility of risk factors such as bone mineral density, lifestyle, and postural stability in the prediction of osteoporotic fractures. DESIGN: Longitudinal, epidemiological, and population based survey. SETTING: City of Dubbo, New South Wales. SUBJECTS: All residents of Dubbo aged > or = 60 on 1 January 1989. MAIN OUTCOME MEASURE: Incidence of fracture for individual subjects. RESULTS: The overall incidence of atraumatic fractures in men and women was 1.9% and 3.1% per annum respectively. The predominant sites of fracture were hip (18.9%), distal radius (18.5%), ribs and humerus (11.9% in each case), and ankle and foot (9.1% and 6.6% respectively). Major predictors of fractures in men and women were femoral neck bone mineral density, body sway, and quadriceps strength. Age, years since menopause, height, weight, and lifestyle factors were also correlated with bone mineral density and body sway and hence were indirect risk factors for fracture. Discriminant function analysis correctly identified 96% and 93% (sensitivities 88% and 81%) of men and women, respectively, who subsequently developed atraumatic fractures. Predictions based on this model indicated that a woman with a bone mineral density in the lowest quartile in the hip together with high body sway had a 8.4% probability of fracture per annum. This represented an almost 14-fold increase in risk of fracture compared with a woman in the highest bone mineral density quartile with low postural sway. An individual with all three predictors in the "highest risk" quartile had a 13.1% risk of fracture per annum. CONCLUSIONS: Bone mineral density, body sway, and muscle strength are independent and powerful synergistic predictors of fracture incidence.

Aged↗
PubMed1993

Oligomerization of the Nef protein from human immunodeficiency virus (HIV) type 1.

The nef genes, derived from two different human immunodeficiency-virus-type-1 (HIV-1) strains, were expressed in procaryotic cells (Escherichia coli) and in eucaryotic cells (insect cells infected with nef-containing baculovirus). The oligomerization of recombinant Nef protein was studied by NMR spectroscopy and immunoblotting under various experimental conditions. 1H-NMR spectroscopy shows that native folded protein has the tendency to polymerize under low-salt conditions. These oligomers become covalently linked by disulfide bonds after decreasing the reduction potential, a process which is fully reversible. Cross-linking studies with bis(sulfo-succinimidyl)suberate and alkylation with iodoacetic acid under non-reducing and reducing conditions document for the first time that Nef can also form homomeric structures including monomers, dimers, trimers and tetramers in cell lysates and intact cells. We found disulfide-linked as well as non-covalently associated oligomers. Since the Nef molecules are not exclusively found in the cytoplasm of HIV infected cells and since the reduced glutathione concentration in lymphocytes of virus infected persons is known to be unusually low, it might be possible that these Nef oligomers have a biological function in vivo as well.

Alkylation↗
PubMed1993

Radiation pneumonitis: a possible lymphocyte-mediated hypersensitivity reaction.

OBJECTIVE: To determine if unilateral thoracic irradiation results in a lymphoid alveolitis in both irradiated and unirradiated lung fields. DESIGN: A prospective, nonrandomized study. PATIENTS: Women receiving postoperative radiotherapy for carcinoma of the breast were evaluated both before and 4 to 6 weeks after radiotherapy. Findings after radiotherapy in 15 asymptomatic patients were compared with findings in a group of patients with clinical radiation pneumonitis. MEASUREMENTS: History, physical examination, chest radiograph, quantitative gallium lung scanning, respiratory function tests, bronchoalveolar lavage, and lavage lymphocyte subset analysis. RESULTS: After irradiation, lavage lymphocytes increased significantly (34.5% versus 46.8%; P = 0.01) in the 17 patients studied prospectively. There was an associated reduction in vital capacity (102.5% versus 95.5%; P = 0.04). Comparison of results in patients before treatment, after treatment without clinical pneumonitis, and after treatment with clinical pneumonitis showed a dramatic increase in total lymphocytes after irradiation (6.3 versus 9.4 versus 35.2 million, respectively; P = 0.005), particularly in those with clinical pneumonitis. Only in those with clinical pneumonitis was this accompanied by an increase in the gallium index (3.7 versus 3.4 versus 9.0, respectively; P < 0.001). Vital capacity was also progressively reduced (102.5% versus 96.9% versus 76.7%, respectively; P = 0.04), as was diffusing capacity (98.6% versus 91.4% versus 72.6%, respectively; P = 0.003). No statistical differences existed between irradiated and unirradiated sides of the chest in either lavage or gallium lung scan studies. CONCLUSION: In most patients, a lymphocytic alveolitis develops in both lung fields after strictly unilateral thoracic irradiation; this is more pronounced in patients developing clinical pneumonitis. These findings suggest that radiotherapy may cause a generalized lymphocyte-mediated hypersensitivity reaction.

Adult↗
PubMed1993

Radionuclide hepatobiliary scanning in patients with AIDS-related sclerosing cholangitis.

Biliary disease, primarily manifesting as papillary stenosis or sclerosing cholangitis, is being increasingly recognized as a problem in the acquired immunodeficiency syndrome (AIDS) and may be amenable to specific treatment. Ultrasound, followed by endoscopic retrograde cholangiopancreatography (ERCP) for definitive diagnosis, is currently the prime mode of investigation of suspected hepatobiliary diseases in AIDS. There are few published reports of the use of radionuclide cholescintigraphy in the assessment of these patients. This report presents Tc-99m DISIDA cholescintigraphy data from three patients with AIDS-related hepatobiliary disease confirmed by ERCP. Radionuclide cholescintigraphy was abnormal in all three patients. In two of the subjects, there was focal duct dilation with strictures in the biliary tree. The third patient demonstrated diffuse hepatic parenchymal retention with marked delay in tracer washout. Two of the subjects, treated with specific anticryptosporidial therapy, subsequently underwent progress cholescintigraphy. In one of these patients with initial diffuse parenchymal retention, there was marked improvement in scan appearances. The second patient with initial duct dilation had no significant change in scan appearances, but quantitative analysis did demonstrate improvement in hepatobiliary tracer clearance rate. In conclusion, although ERCP remains the gold standard in the diagnosis of AIDS-related biliary disease, radionuclide cholescintigraphy may be a useful modality in these patients as a screening test before proceeding to more expensive and invasive techniques. In addition, quantitative analysis of cholescintigraphy may allow assessment of patient response to specific antimicrobial or surgical intervention.

Acquired Immunodeficiency Syndrome↗
PubMed1992

A method for the detection of serologically crossreacting antigens both within and between protein mixtures: the western cross blot.

The method described in the present paper permits the detection of antigenically related proteins within or between different antigen mixtures. For this purpose two separate SDS-polyacrylamide gels are run (the antigen mixture is applied to the entire width of the gel) and each gel is blotted on to a separate nitrocellulose paper. One sheet ('donor sheet') is incubated with antiserum and placed on to the other blot ('receptor sheet') so that the antigen bands are perpendicular to each other. Subsequently the antibodies from the donor sheet are blotted on to the receptor sheet in alkaline borate buffer containing 1 M NaSCN, which dissociates antigen-antibody complexes. After the removal of the donor sheet the receptor sheet containing the transblotted antibodies is equilibrated in phosphate-buffered saline in order to reconstitute the binding conditions. Antibodies which have bound to receptor antigens during this equilibration period are detected by the use of a peroxidase labelled 2nd antibody. Because each band on the donor sheet crosses each band on the receptor sheet during the transfer, the antibodies from each band of the donor sheet are able to react with each antigen band of the receptor sheet. The validity of the method was established by demonstrating the crossreactivity of a polyclonal antiserum against the intact bovine gamma globulin molecule with the heavy and light chain subunits (and partial reduction products of the molecule) and the absence of crossreactivity between heavy and light chains. In a second experiment crossreacting antigens of different molecular weight were detected within several strains of Escherichia coli. In addition, comparisons of different strains of Escherichia coli revealed crossreacting antigens of identical as well as of different molecular weight.

Blotting, Western↗