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Biomedical subjects

L Landin

Publications and source records attributed to L Landin.

13 recordsLinked to original sources
PubMed2006

Infrared photodetectors in heterostructure nanowires.

We report on spectrally resolved photocurrent measurements on single self-assembled nanowire heterostructures. The wires, typically 3 microm long with an average diameter of 85 nm, consist of InAs with a 1 microm central part of InAsP. Two different sets of wires were prepared with phosphorus contents of 15+/-3% and 35+/-3%, respectively, as determined by energy-dispersive spectroscopy measurements made in transmission electron microscopy. Ohmic contacts are fabricated to the InAs ends of the wire using e-beam lithography. The conduction band offset between the InAs and InAsP regions virtually removes the dark current through the wires at low temperature. In the optical experiments, interband excitation in the phosphorus-rich part of the wires results in a photocurrent with threshold energies of about 0.65 and 0.82 eV, respectively, in qualitative agreement with the expected band gap of the two compositions. Furthermore, a strong polarization dependence is observed with an order of magnitude larger photocurrent for light polarized parallel to the wire than for light polarized perpendicular to the wire. We believe that these wires form promising candidates as nanoscale infrared polarization-sensitive photodetectors.

Arsenicals↗
PubMed1999

Decreasing incidence of fractures in children: an epidemiological analysis of 1,673 fractures in Malmö, Sweden, 1993-1994.

The incidence of fractures in children in the city of Malmö, Sweden, almost doubled between 1950 and 1979. To see whether a further increase had occurred, we carried out an epidemiological analysis of fractures among children 0-16 years in Malmö 1993-1994. During the study period, 1,673 fractures occurred in 1,610 children. The commonest fracture location was the distal forearm (26%), followed by the phalanges of the hand (16%) and the clavicle (9%). The annual fracture incidence was 235/10(4) in boys, 149/10(4) in girls and 193/10(4) for both genders. This means a decrease in the annual fracture incidence by 9% since 1975-1979. The decrease was not associated with any specific type of fracture or etiological factor. Fractures of the distal forearm among girls were an exception to the general decline, having increased by one third since 1975-1979, which might be explained by the fact that today girls participate to a greater extent in the same sports as boys.

Adolescent↗
PubMed1998

Optical studies of individual InAs quantum dots in GaAs: few-particle effects

Optical emission from individual strained indium arsenide (InAs) islands buried in gallium arsenide (GaAs) was studied. At low excitation power density, the spectra from these quantum dots consist of a single line. At higher excitation power density, additional emission lines appeared at both higher and lower energies, separated from the main line by about 1 millielectron volt. At even higher excitation power density, this set of lines was replaced by a broad emission peaking below the original line. The splittings were an order of magnitude smaller than the lowest single-electron or single-hole excited state energies, indicating that the fine structure results from few-particle interactions in the dot. Calculations of few-particle effects give splittings of the observed magnitude.

Journal Article↗
PubMed1997

Pituitary-thyroid function in patients with septic shock and its relation with outcome.

OBJECTIVE: To study the time course of thyroid function abnormalities and their relation to outcome in patients with septic shock. DESIGN: Prospective study in a cohort of consecutive patients. SETTING: Intensive Care Unit in a University Hospital. PATIENTS AND METHODS: We studied 27 patients (mean age 50 +/- 19 years, Apache II score 18.4 +/- 5.2, 15 survivors) diagnosed of septic shock. Total T4 (T4) and total T3 (T3) (RIA) were determined on days 1 and 5 after admission. We also measured TSH (ultrasensitive RIA) at 08.00, 20.00 and 01.00 hours (on days 1 and 5), and the TSH response to TRH (400 microg intravenous) on days 2 and 6. Data are mean +/- SD. RESULTS: Whereas low thyroid hormones concentrations were present on day 1 in all patients, only survivors presented a significant increase in T3 and T4 on day 5. Basal TSH levels and the area under the curve of the TSH response to TRH on day 2 were significantly higher in survivors than in non survivors (0.89 +/- 0.63 vs. 0.34 +/- 0.42 microIU/ml, and 229 + 157 vs. 101 + 101). The normal nocturnal (01.00 hr) surge of TSH (the difference between TSH concentrations at 8 am and at 1 am) was abolished in both survivors and non survivors on day 1 but it was recovered on day 5 only in survivors. CONCLUSIONS: Our data indicate that patients with septic shock present an altered hypothalamic-pituitary-thyroid axis, and that survivors thyroid function differs from that of non survivors shortly after diagnosis. Survivors are characterised by a greater TSH response to TRH, indicating a less deranged hypothalamic-pituitary-thyroid axis. Thyroid function improves in survivors, but not in non survivors, during the course of their illness.

Adult↗
PubMed1996

Identification and characterization of glima 38, a glycosylated islet cell membrane antigen, which together with GAD65 and IA2 marks the early phases of autoimmune response in type 1 diabetes.

Immunoprecipitating IgG autoantibodies to glutamic acid decarboxylase, GAD65, and/or a tyrosine phosphatase, IA2, are present in the majority of individuals experiencing pancreatic beta cell destruction and development of type 1 diabetes. Here we identify a third islet cell autoantigen, a novel 38-kD protein, which is specifically immunoprecipitated with sera from a subset of prediabetic individuals and newly diagnosed type 1 diabetic patients. The 38-kD autoantigen, named glima 38, is an amphiphilic membrane glycoprotein, specifically expressed in islet and neuronal cell lines, and thus shares the neuroendocrine expression patterns of GAD65 and IA2. Removal of N-linked carbohydrates results in a protein of 22,000 Mr. Glima 38 autoantibodies were detected in 16/86 (19%) of newly diagnosed patients, including three very young children, who had a rapid onset of disease, and in 6/44 (14%) of prediabetic individuals up to several years before clinical onset. The cumulative incidence of GAD65 and glima 38 antibodies in these two groups was 83 and 80%, respectively, and the cumulative incidence of GAD65, glima 38, and IA2 antibodies in the same groups was 91 and 84%, respectively. GAD65, IA2, and glima 38 represent three distinct targets of immunoprecipitating IgG autoantibodies associated with beta cell destruction and type 1 diabetes.

Adolescent↗
PubMed1996

Effects of nitric oxide synthase inhibition on the cardiovascular response to low output shock.

OBJECTIVE: To study the role of nitric oxide in the cardiovascular response to a model of a low output syndrome. DESIGN: Prospective animal study. SETTING: Animal research laboratory. SUBJECTS: Sheep anesthetized with pentobarbital, mechanically ventilated, and monitored with pulmonary arterial and peripheral arterial catheters. INTERVENTIONS: A low output state was induced by inflating a balloon-tip catheter placed in the right atrium. Cardiac index was maintained at 1 L/min/m2 throughout the experiment in three groups of sheep: a) control (n=6) b)LNNA group (pretreated with the nitric oxide synthase inhibitor N omega-nitro-L-arginine [LNNA, 100 mg/kg, iv bolus, n=6); and c) dexamethasone group (pretreated with dexamethasone (6 mg/kg, intravenous bolus, n=6). Dexamethasone is an inhibitor of the induction of nitric oxide synthase. LNNA or dexamethasone were administered 15 mins before inducing the low output state. MEASUREMENTS AND MAIN RESULTS: Hemodynamic and oxygen transport variables, and plasma lactate and pyruvate concentrations, were measured at baseline and during the next 3 hrs. For a comparable decrease in cardiac index and oxygen delivery in all groups, the LNNA group had less hypotension and a more marked increase in systemic vascular resistance as compared with the control group. Oxygen consumption and oxygen extraction were higher in the LNNA group as compared with the control group at 30 and 60 mins. Plasma lactate concentration increased significantly less in the LNNA group than in the control and the dexamethasone groups during the observation period. CONCLUSIONS: Inhibition of nitric oxide synthesis during a severe low output state in sheep is associated with a better hemodynamic response, as evidenced by a greater vasoconstriction, and signs of less marked tissue hypoxia. It is likely that inhibition of nitric oxide synthesis in this model leads to an imbalance between the tonic relaxing action of nitric oxide and the influences of vasoconstrictor agents.

Analysis of Variance↗
PubMed1992

Hemodynamic changes in the dog connected to a dialysis circuit: influence of the body temperature.

Eighteen sessions in 9 mongrel dogs were carried out to know the hemodynamic effects produced by body temperature variation, when blood passes through a dialysis circuit with a Cuprophan dialyzer, without dialysate contact. The decrease of 2 degrees C in body temperature caused a decrease in heart rate and cardiac index (-8.6 and -17.6%, respectively) without significant changes in blood pressure. The increase of 2 degrees C in body temperature increased the heart rate, the cardiac index and the first derivative of ventricular pressure (+14.8, +17.3 and +27.8%, respectively) with a decrease of 13.6% in the systemic vascular resistance. Blood pressure did not change significantly. We conclude that the dog maintains the hemodynamic stability by two different mechanisms: when body temperature rises, by increasing the cardiac index; when body temperature decreases, by increasing the systemic vascular resistance.

Animals↗
PubMed1987

Changes in fibrinolysis in the intensive care patient.

Critically ill patients have been described as having blood coagulation abnormalities that predispose to bleeding and thrombosis. We have studied plasminogen activators, alpha 2-antiplasmin, X-oligomers fibrin fragments, fibronectin, antithrombin III, fibrinogen, platelets, kaolin-cephalin clotting time and prothrombin time on admission to the intensive care unit and sequentially after 24 and 48 hours in 39 adult patients: ARDS (n = 6), trauma (n = 12), sepsis (n = 8) and a miscellanea (n = 13). A decrease in plasminogen activators associated with an increase in X-oligomers, the earliest form of cross linked fibrin degradation products, indicate that fibrin deposition and the consumption of components of fibrinolysis is a widespread condition in the ICU patients. Low fibronectin levels were related to prognosis. These findings suggest that critically ill patients must be evaluated in respect to fibrinolysis and supported when necessary with prophylactic treatment.

Adolescent↗
PubMed1984

A syndrome of gonadotropin resistance possibly due to a luteinizing hormone receptor defect.

An 18-yr-old 46,XY man with primary hypogonadism and a microphallus is described whose Leydig cells appear to be partially insensitive to gonadotropin action. The external genitalia were well differentiated though abnormally small. The mean +/- SE baseline plasma testosterone (T) level was 62 +/- 3.9 ng/dl, and androstenedione was 34.5 +/- 7.3 ng/dl. Plasma levels of dehydroepiandrosterone, dehydroepiandrosterone sulfate, 17-hydroxyprogesterone, 17-hydroxypregnenolone, corticosterone, deoxycorticosterone, and 17 beta-estradiol were all normal. After the im administration of hCG, plasma T increased insignificantly from 71 to 78 ng/dl, and androstenedione increased from 22 to 47 ng/dl; there was no significant change in the levels of precursor steroids. The mean +/- SE serum FSH level was 17.4 +/- 3.6 mIU/ml, and LH was 15.4 +/- 1.1 mIU/ml (normal, 5-20); both responded briskly to iv GnRH. Exogenous T therapy resulted in normal virilization, whereas therapy with hCG was ineffectual. Testicular biopsy revealed Leydig cells in normal numbers, some spermatogenesis, and thickened tubular basement membranes. In vitro binding studies using [125I]hCG were performed with testicular homogenates from the patient and three normal subjects. With 7.4 fmol labeled hCG, the specific binding (mean +/- SD), expressed as femtomoles of hCG per mg protein, was 1.16 +/- 0.44 compared to 2.49 +/- 0.41 in normal subjects (P less than 0.05). These data demonstrate partial resistance to hCG and suggest that the defect in Leydig cell function may be at the LH receptor or postreceptor level.

Adolescent↗
PubMed1983

Bone mineral content in children with fractures.

Bone mineral content was measured in the forearms of 90 children who had recent fractures. The data were compared with those of age-matched healthy children. Bone mineral content was significantly reduced in children in whom fractures were caused by low-energy trauma. Bone mineral content in children in whom fractures were caused by high-energy trauma was also reduced, but the difference was not significant. Correction for other parameters of growth and maturation, e.g., height and weight, did not eliminate the difference in bone mineral content. These findings indicate that endogenous factors contribute to fracture not only in the elderly but also in children.

Adolescent↗
PubMed1981

Forearm bone mineral content in children. Normative data.

The bone mineral content in the forearm was measured by gamma-absorptiometry in 131 normal children. The bone mineral content was closely related to age, height and weight, to the size of forearm and to the force of the forearm muscles. By correcting for the dimensions of the bones a parameter of density (mass/volume) was calculated. This variable also increased with age. Knowing the necessary corrections factors gamma-absorptiometry could be a useful and harmless method for bone mineral assessment in children with various diseases.

Adolescent↗