Biomedical subjects
Publications and source records attributed to M Hammer.
Fc gamma-receptor-(CD16-)positive natural killer (NK) cells are activated by rheumatoid factor in the synovial fluid of patients with rheumatoid arthritis. This activation induces modulation of the CD16 molecule and release of IFN gamma and TNF alpha by NK cells.
An important mechanism that contributes to sensitization in Aplysia is heterosynaptic facilitation of the synaptic connections between sensory neurons (SNs) and motor neurons (MNs). Heterosynaptic facilitation, in turn, is associated with broadening of the spike in the SN. Spike broadening is readily observed in recordings from somata of SNs, and from growth cones of SNs in culture, but broadening in synaptic terminals has only been inferred. Intracellular recordings were made from somata of SNs and from somata of follower MNs. Additional recordings were made from the axons of SNs as they enter the neuropil in the pedal ganglion. Serotonin (5-HT) broadened action potentials in axons of SNs and enhanced excitatory postsynaptic potentials (EPSPs) in the MNs, even after the axons of SNs were surgically separated from their somata. These results indicate that both heterosynaptic facilitation and spike broadening in the axon are due to the local action of 5-HT and can occur independently of modulation of membrane properties in the soma.
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Among 256 examined gastric biopsies from 200 adolescents, inflammatory changes were found strikingly often: 44.5% showed chronic superficial gastritis without atrophic processes. However, the percentage of biopsies of normal mucosa was substantially higher than that of a compared series of biopsies not selected according to age of the patients. According to our findings in adolescents, the interstitial stroma of normal gastric mucosa in the antrum, as well as in the corpus, was absolutely free of round cells. Bacterial colonization with Campylobacter-like organisms (CLO) occurred almost as frequently as in the series not selected according to age. Consequently, the biopsy material of adolescents substantially more often featured normal mucosa with bacterial colonization, mostly of the minimal focal variety, than did the compared series. Colonization with CLO apparently takes place at an early age, and may exacerbate into a massive colonization.
Different non-hypotensive hypovolemic stimuli were applied to 21 healthy and 20 uremic dialysis patients. The purpose was to study the effect on plasma arginine-vasopressin concentration, using orthostasis as a reference model. Orthostasis increased the plasma AVP level in healthy subjects as well as in uremic dialysis patients. In healthy subjects plasma AVP increased both when they were normohydrated and after they had been water-depleted. Lower body negative pressure (LBNP, -40 mmHg) was applied to 11 healthy males to induce a central blood volume decrease, equal to that induced by orthostasis. The plasma AVP increased in two subjects only who became hypotensive during the investigations. Ten hemodialysis patients were volume-depleted by isolated ultrafiltration. A flow directed Swan-Ganz catheter was used to measure the central intravascular pressures. Pulmonary capillary wedge pressure was reduced to normal or subnormal values during 1-2 h of ultrafiltration, without any significant changes in plasma AVP. Plasma AVP increased only in 2 patients, who became hypotensive during the investigations. Thus, of the present non-hypotensive volume stimuli only orthostasis was able to stimulate AVP secretion. Equal or even greater reductions in central blood volumes by other stimuli had no effect on AVP secretion. The results demonstrate that isolated stimulation of low-pressure volume receptors has no effect on the secretion of AVP in humans.
Urate concentrations in serum and renal urate clearance were prospectively evaluated in patients with small cell lung cancer (SCLC). Serum urate and renal urate clearance were measured before and during cytostatic treatment until disease progression (PD) in 12 patients with the syndrome of inappropriate antidiuresis (SIAD) and in 8 patients without. Hypouricemia occurred in 4 SIAD patients before treatment and also when tumor regression was obtained. Two normouricemic SIAD patients developed hypouricemia when PD occurred. No patient without SIAD experienced hypouricemia. Serum urate in patients with SIAD was lower than in those without SIAD before cytostatic treatment but not 3 months after the treatment. Hypouricemic patients had higher urate clearance than normouricemic and it remained higher even after tumor regression. Serum urate was invalid as marker of tumor regression or relapse. SIAD patients have higher glomerular filtration rates than patients without SIAD, which may influence the renal excretion of cytostatic drugs.
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Mouse t haplotypes are variant forms of chromosome 17 that exist at high frequencies in worldwide populations of two species of commensal mice. To determine both the relationship of t haplotypes to each other and the species within which they exist, 35 representative t haplotypes were analyzed by means of 10 independent molecular probes, including five DNA clones and five polypeptide spots identified by means of two-dimensional gel electrophoresis. All of the tested haplotypes were found to share restriction fragments and polypeptide spots that are absent in mice carrying wild-type forms of chromosome 17. This observation provides the first direct evidence that all of the known t haplotypes are descendents of a single ancestral chromosome. The absence of variation among t haplotypes could mean that this ancestral chromosome existed relatively recently, in which case it would be necessary to postulate introgressions of t haplotypes across species lines to explain their presence in both Mus domesticus and M. musculus. Alternatively, it is possible that the ancestral chromosome existed prior to the split between M. domesticus and M. musculus and that, by chance, our probes fail to detect polymorphisms that exist among the t haplotypes. A further result of our analysis is the characterization of a partial t haplotype in a wild population of Israeli mice.
Patients with small-cell lung cancer and hyponatremia were examined for the syndrome of inappropriate antidiuresis (SIAD). A comparison was made between the definition based on hyponatremia, serum hypoosmolality and urine hyperosmolality (classic SIAD, 12 patients) and a definition based on measurement of plasma ADH concentration by radioimmunoassay (RIA-SIAD, nine patients) and patients without SIAD (eight patients). A standard water load test was performed as a reference before initiation of cytostatic treatment. All tests were repeated if remission of the malignant disease occurred. RIA-SIAD patients were a subgroup of classic SIAD patients, with more pronounced homeostatic abnormalities. Biochemical abnormalities were reduced after tumor regression but a completely normal renal water handling was achieved in only few patients, even when complete remission of the tumor was achieved, presumably due to the persistence of subclinical disease. However, an effect of other yet unknown factors might be of influence.
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For two years all 28 patients undergoing hospital haemodialysis were switched from a dialysate magnesium (Mg) of 0.85 mmol/l to one containing none. Oral aluminium hydroxide was discontinued, and magnesium carbonate was substituted as a phosphate binder. After 24 months on this regimen predialysis aluminium concentration had fallen significantly. There was no significant change in predialysis phosphate, which remained above the normal range; nor was there evidence of increased secondary hyperparathyroidism as judged by parathyroid hormone immunoassay and biochemical or clinical criteria. Predialysis Mg concentrations tended to fall towards the normal range. Aluminium-containing phosphate binders seem to be unnecessary for the control of dialysis hyperphosphataemia. Magnesium carbonate may be an alternative and less toxic compound.
Deoxyribonucleic acid sequences specific for a pathogen of interest can be isolated from a variety of microorganisms. Such DNA probes can be exploited to detect infectious agents directly in infected patient material despite the presence of large numbers of other organisms and host DNA. This technology is dependent upon the recognition of a specific nucleotide sequence present in DNA extracted from a clinical sample by a radiolabeled or nonisotopically labeled DNA probe. We have isolated several DNA probes for the detection of pathogenic Neisseria which include a plasmid species unique to the gonococcus, as well as several cloned genes that detect both the gonococcus and the meningococcus. In addition, we characterized a unique plasmid of Chlamydia trachomatis that has proved to be quite useful as a DNA probe for the detection of this pathogen in cervical secretions and, by in situ hybridization, in Papanicolaou smears. Deoxyribonucleic acid hybridization as a diagnostic tool is still in its infancy. It holds a number of advantages over conventional methods of pathogen detection and serves as an alternative, as well as a complement, to available immunologic methods.
The effect of vasopressin (AVP) on subcutaneous blood flow was studied by the 133Xenon wash-out method in 13 healthy subjects during three consecutive infusions of synthetic AVP, using increasing infusion rates. In seven of them, both subcutaneous and skeletal muscle blood flows were measured during the first infusion. The preinfusion, and infusion pAVP levels were 1.6 +/- 0.4, 3.4 +/- 0.4, 4.9 +/- 0.5 and 8.8 +/- 0.7 pg ml-1, respectively (mean +/- SE). The values are within the range normally found during dehydration. During the AVP infusions, the blood flow in subcutaneous tissues decreased 30-40% and the vascular resistance increased 60-80%. Neither heart rate nor blood pressure change significantly during the infusions. Plasma renin activity (PRA) decreased significantly. After cessation of the infusions, blood flow and vascular resistance rapidly returned to preinfusion values, while PRA increased very slowly. Skeletal muscle and subcutaneous tissues blood flows were found to be equally sensitive to small changes in the pAVP level. The present study has demonstrated that even minor increments of pAVP levels, as seen during dehydration, can significantly alter the regional blood flow in subcutaneous and skeletal muscle tissues in man.
Sonography and NMR imaging of the knee joint make it possible to obtain a visual representation of the thickened synovial membrane occurring in patients with rheumatoid gonarthritis, even before inflammatory deformation is radiologically detectable. Both methods can expose effusions and Baker's cysts. In NMR imaging, an indication of the inflammatory genesis can be obtained from the extended relaxation time T1. Due to the good representation of soft tissues, prognostic evidence may be gained of whether a mainly exudative or proliferative form is present.
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A single injection of an aqueous suspension of group A streptococcal peptidoglycan-polysaccharide complexes (PG-PS) when injected intraperitoneally into Lewis rats induced a self-limiting bilateral uveitis with associated perpetuating polyarthritis. The uveitis was characterized clinically during the first 72 h by iritis and fibrin deposition. Acutely, there was infiltration of polymorphonuclear cells. The symptoms gradually subsided, and at the close of the experiment eyes were normally clinically and histologically. In contrast, perpetuating inflammation and severe tissue injury developed in the limb. Using an enzyme immunoassay with specificity for the group A streptococcal polysaccharide, the levels of PG-PS in tissues of animals that were killed 1 to 7 days post-injection were measured. The relative amounts of antigen in eye:limb:liver of PG-PS injected animals were 1:9:170. The differences in the amounts of antigen detected in the eye and limb may help explain the development of the acute uveitis in contrast to the perpetuating polyarthritis observed on PG-PS administration. The authors suggest that bacterial debris may act similarly in causing ocular inflammation in man.
This investigation demonstrates an abnormal response to the adrenal cortex to modulation of the potassium metabolism by an intravenous infusion of insulin-glucose in patients with essential hypertension. In response to insulin-glucose there was a transient decline of plasma aldosterone and plasma cortisol concentrations in control subjects with normal blood pressure, whereas a temporary increase of both hormones was found in patients with essential hypertension. Treatment with thiazide diuretics further magnified the different aldosterone response between the two groups. It is suggested that the abnormal response of patients with essential hypertension may be of significance to the understanding of the pathogenesis of this important disease.