Inhibitor of granulopoiesis in human cyclic neutropenia.

Peripheral blood mononuclear cells of a patient with cyclic neutropenia release a high molecular weight substance (over 300,000) inhibiting normal CFU-GM cells to enter the S-phase of cell cycle. The inhibitor was released predominantly in the neutropenic phase of the disease, while in the period of normal granulocyte count the release was lower or undetectable. Also sensitivity of patient's bone marrow CFU-GM cells to similar high molecular weight inhibitor produced by ML-2 cell liner or to human placental ferritin varied within the disease cycle. CFU-GM in the normal granulocyte count period were sensitive to the inhibitors, but CFU-GM in the neutropenic phase were resistant.     

Regulation of human B lymphopoiesis: effect of a urinary activity associated with cyclic neutropenia

Urine from a patient with cyclic neutropenia was found to contain a lymphopoietic activity that acts as a growth factor for human pre-B cells. This biologic activity was detectable during the week preceding, but not during, the period of neutropenia. This corresponded with a periodic excessive accumulation of pre-B cells in the marrow of this patient. Urine preparations were added to cultures of normal human bone marrow that had been depleted of B cells. Pre-B cells were generated in these cultures but not in cultures containing urine preparations from normal donors. Pre-B cells were also generated from bone marrow that had been depleted of 177.17+ cells and the majority of pre-B cells. This is the first report of a hemopoietic activity which affects human pre-B cells. This activity may represent a normal regulatory molecule that is periodically produced in excess in this patient.     

The variance of transit times of indicators through a vascular bed

A new method is developed of determining the variance of the times of transit of an indicator through a vascular bed (or through any perfused organ) from the time-course of the arterial-venous concentration difference, observed between two steady states. The method is illustrated using previously published data on arterial and hepatic venous radioactivities following a single injection of ¹³¹I-labelled serum albumin in man.     

A possible pathomechanism of the idiopathic cold contact urticaria.

Urtica is characterized by an erythematous wheal surrounded by a flare and is frequently caused by physical agents (e.g. cold). The exact mechanism and mediators involved in the mechanism of physical urticaria are not known. This study of the role of the neurogenic factors in cold urticaria showed, that local capsaicin treatment (desensitization) of the skin in patients with cold urticaria resulted in the abolition of whealing in response to cold. This result suggests that C-fibers might play an important role in the pathomechanism of idiopathic contact cold urticaria.     

Clinical effect of recombinant human granulocyte colony-stimulating factor (rhG-CSF) on various types of neutropenia including cyclic neutropenia

Recombinant human granulocyte colony-stimulating factor (rhG-CSF) was investigated for its clinical efficacy in the treatment of various types of neutropenia (3 cases with idiopathic neutropenia of suspected drug induction, 5 cases with idiopathic neutropenia of other origin, and 2 cases with cyclic neutropenia). Treatment with glycosylated rhG-CSF produced in the Chinese Hamster Ovary cells at dose levels of 2–5g/kg/day caused rapid increases of neutrophil counts associated with an improvement of the infection. In cyclic neutropenia patients, marked reduction in the duration of the neutropenic period was observed with rhG-CSF administration started before the period. Intercurrent stomatitis, which occurred in 1 patient, was markedly milder as compared to a previous episode which occurred during an untreated neutropenic period.The treatment of rhG-CSF was well tolerated and no adverse events were observed, nor was there any detectable anti-rhG-CSF antibody in any patients studied; hence the clinical use of rhG-CSF is considered to be safe.These results suggest beneficial effects of rhG-CSF on the recovery of neutrophil counts in cyclic and other types of idiopathic neutropenias, as well as for the treatment of neutropenia-associated infection.     

The diffusion transit time; A simple derivation

The mean first passage time for free diffusion can be derived directly by solving a simple analogue steady state problem. In this problem the diffusion starting region is considered as a time independent source of diffusing particles and the diffusion target assumes the behaviour of a perfectly absorbing sink. It is shown here that the transit time between the source and the sink, which in this particular problem is equal to the ratio between the holdup of the system and the total flux, is identical to the Brownian movement concept of the mean first passage time for free diffusion. This established identity considerably facilitates the derivation and investigation of the timing of diffusion in complicated structures such as those commonly found in living organisms.     

Gastro‐Intestinal transit time in South American deer

The study of diet and physiological peculiarities of the digestive system of neotropical deer is not well known and the literature shows inconsistencies. To better understand the digestive system of these mammals the difference in the gastro‐intestinal transit time of four species of neotropical deer (Mazama americana, Mazama gouazoubira, Mazama nana, Blastocerus dichotomus), kept in captivity, was evaluated. Four plants (Neonotonia wightii, Morus albans, Medicago sativa, Leucaena leucocephala) were utilized and two variables were measured, mean time of the beginning of the elimination (BE) and mean time of permanence (TP). The results obtained for BE indicated similarity among the deer species, with significant differences between M. gouazoubira (mean=13.62 hr) and M. Americana (mean=19.25 hr). For the plants, the BE was faster with N. wightii and L. leucocephala, and slower for M. sativa. The TP results for B. dichotomus showed longer time when compared to the other species, whereas M. gouazoubira had a lower permanence. Overall, N. wightii had the highest retention time in the digestive tract of all the deer species studied. Associated with this observation, N. wightii had the highest quantity of plant fiber of the plants tested. In a similar fashion M. sativa showed the lowest TP in the digestive tract of the deer and had the lowest quantity of acid detergent fiber. The data from this study showed that, within species, the shape of the excretion curve of the plants was similar when the animals consumed N. wightii or M. sativa. Blastocerus dichotomus and M. gouazoubira had the highest and the lowest gastro‐intestinal transit time, respectively. This suggests that these species characterize different abilities to digest high fiber food, and consequently, represent the two extremities in the morphophysiological adaptation within the deer species evaluated. This information is vital because it is important to know the digestive physiology to define the diet of captive animals, particularly regarding the quantity and quality of fiber. Zoo Biol 0:1–11, 2005. © 2005 Wiley‐Liss, Inc.     

Asymptotically robust variance estimation for person‐time incidence rates

Person‐time incidence rates are frequently used in medical research. However, standard estimation theory for this measure of event occurrence is based on the assumption of independent and identically distributed (iid) exponential event times, which implies that the hazard function remains constant over time. Under this assumption and assuming independent censoring, observed person‐time incidence rate is the maximum‐likelihood estimator of the constant hazard, and asymptotic variance of the log rate can be estimated consistently by the inverse of the number of events. However, in many practical applications, the assumption of constant hazard is not very plausible. In the present paper, an average rate parameter is defined as the ratio of expected event count to the expected total time at risk. This rate parameter is equal to the hazard function under constant hazard. For inference about the average rate parameter, an asymptotically robust variance estimator of the log rate is proposed. Given some very general conditions, the robust variance estimator is consistent under arbitrary iid event times, and is also consistent or asymptotically conservative when event times are independent but nonidentically distributed. In contrast, the standard maximum‐likelihood estimator may become anticonservative under nonconstant hazard, producing confidence intervals with less‐than‐nominal asymptotic coverage. These results are derived analytically and illustrated with simulations. The two estimators are also compared in five datasets from oncology studies.     

Colony-stimulating activity in urine and serum in a child with cyclic neutropenia]

Colony stimulating activity (CSA) was estimated in daily urine samples and weekly plasma specimens of a 4-year-old girl with familial cyclic neutropenia. Nadirs of neutrophils and peaks of monocytes were found in regular cycles of 28 days. A close correlation was observed between nadirs of neutrophils and peaks of blood monocytes and colony stimulating activity in the urine. The role of colony stimulating factor as regulatory factor in granulopoiesis in cyclic neutropenia is discussed.     

Phytanic acid disturbs mitochondrial homeostasis in heart of young rats: a possible pathomechanism of cardiomyopathy in Refsum disease

Phytanic acid (Phyt) accumulates in tissues and biological fluids of patients affected by Refsum disease. Although cardiomyopathy is an important clinical manifestation of this disorder, the mechanisms of heart damage are poorly known. In the present study, we investigated the in vitro effects of Phyt on important parameters of oxidative stress in heart of young rats. Phyt significantly increased thiobarbituric acid-reactive substances levels (P < 0.001) and carbonyl formation (P < 0.01), indicating that this fatty acid induces lipid and protein oxidative damage, respectively. In contrast, Phyt did not alter sulfhydryl oxidation. Phyt also decreased glutathione (GSH) concentrations (P < 0.05), an important non-enzymatic antioxidant defense. Moreover, Phyt increased 2',7'-dichlorofluorescin oxidation (DCFH) (P < 0.01), reflecting increased reactive species generation. We also found that the induced lipid and protein oxidative damage, as well as the decreased GSH levels and increased DCFH oxidation provoked by this fatty acid were prevented or attenuated by the reactive oxygen species scavengers melatonin, trolox, and GSH, but not by the nitric oxide inhibitor N: (ω)-nitro-L: -arginine methyl ester, suggesting that reactive oxygen species were involved in these effects. Next, we verified that Phyt strongly inhibited NADH-cytochrome c oxidoreductase (complex I-III) activity (P < 0.001) in heart supernatants, and decreased membrane potential and the NAD(P)H pool in heart mitochondria, indicating that Phyt acts as a metabolic inhibitor and as an uncoupler of the electron transport chain. Therefore, it can be presumed that disturbance of cellular energy and redox homeostasis induced by Phyt may possibly contribute to the cardiomyopathy found in patients affected by Refsum disease.     

Error analysis of classic colonic transit time estimates

Estimates of colonic transit times (CTT) through the three colonic segments, right colon, left colon, and rectosigmoid, are commonly based on radiopaque markers. For a given segment, CTT is usually calculated from just the number of markers visible in that segment on abdominal X-rays. This procedure is only strictly valid for the theoretical, but unrealistic, case of continuous marker ingestion (i. e., not for a single or once-daily ingestion). CTT was analyzed using the usual estimate of the mean CTT of one marker and also using a new, more realistic estimate based on the kinetic coefficients of a three-compartment colonic model. We directly compared our compartmental approach to classic CTT estimates by double-marker studies in six patients. We also retrospectively studied CTT in 148 healthy control subjects (83 males, 65 females) and 1,309 subjects with functional bowel disorders (irritable bowel syndrome or constipation). Compared with the compartmental estimates, the classic approach systematically underestimates CTT in both populations, i.e., in patients and in healthy control subjects. The relative error could easily reach 100% independent of the site of colonic transit delay. The normal values of total CTT are then 44.3+/-29.3 instead of 30.1+/-23.6 h for males and 68.2+/-54.4 instead of 47.1+/-28.2 h for females.     

Direct effect of parathyroid hormone on the proliferation of osteoblast-like cells; a possible involvement of cyclic AMP

Serum-starved chick osteoblast-like cells (OB cells) and periosteal fibroblasts (PF cells) were used to study the proliferative effects of parathyroid hormone (PTH) and prostaglandin E2 (PGE2). Both PTH (10(-11) to 10(-8) M) and PGE2 (10(-9) to 10(-5) M) had a direct, dose-related effect on the de novo synthesis of DNA in OB cells. The PF cells only showed a dose-dependent effect in the presence of PGE2 (10(-9) to 10(-5) M). The hormonally induced proliferation of these cells was shown to be dependent on cell density and stimulation time. An optimal response for both cell types was observed in the cell density range 1.5 to 3.5 micrograms DNA/2 cm2, when stimulated for 18 hours. As cAMP-enhancing substances (N6-dBcAMP, forskolin and IBMX) could mimic the PTH- and PGE2-induced proliferation in OB cells, the increased DNA synthesis was concluded to be mainly caused by enhanced cAMP concentrations.     

Determination of pulmonary mean transit time and cardiac output using a one-dimensional model

In this work, we show that a one-dimensional model of the blood flow across the lungs can reproduce the evolution of a bolus versus the time. Solving the differential equation governing the bolus concentration in the framework of this model, we determine the solution which fulfills Gaussian initial boundary conditions. An effective parameter related to the ratio of a diffusion coefficient to the square of the mean speed of the flow is defined. The determination of its numerical values following a semi-empirical approach enables us to know accurately the mean transit time and the cardiac output. The results have been compared to other methods, and were found in good agreement. Such an approach could be of interest in all studies where the knowledge of flow—including micro-circulation—is needed.     

Evidence for integrin receptor involvement in megakaryocyte-fibroblast interaction: A possible pathomechanism for the evolution of myelofibrosis

Megakaryocytes are assumed to be functionally linked with the evolution of myelofibrosis, complicating chronic myeloproliferative disorders. It has already been shown that megakaryocytes will promote fibroblast growth in vitro when in spatial proximity. Here, we demonstrate that the integrin receptors α3β1 and α5β1 are involved in this megakaryocyte-fibroblast interaction. Upon addition of anti-α3 and -α5 antibodies to megakaryocyte-fibroblast cocultures, fibroblast growth was significantly impaired, and megakaryocyte attachment to the fibroblast feederlayer was significantly reduced. Unilateral blocking of megakaryocytes with anti-α3 or -α5 antibodies resulted in a suppression of adhesion, probably reflecting the prominent function of fibronectin receptors on the megakaryocyte surface. Moreover, the oligopeptide RGDS (Asp-Gly-Asp-Ser) caused a significant reduction of fibroblast growth as well as megakaryocyte adhesion. This feature reinforces that fibronectin receptors are involved. In addition, fibroblast proliferation was impaired by the application of fibronectin antibodies recognizing the cell-binding domain. However, no effect was observable with respect to megakaryocyte adhesion. In conclusion, our in vitro studies demonstrate the involvement of β1-integrins, in particular the fibronectin receptor in the megakaryocyte-dependent fibroblast proliferation and therefore suggest a pivotal role of megakaryocytes in the complex pathomechanism causing myelofibrosis. J. Cell. Physiol. 176:445–455, 1998. © 1998 Wiley-Liss, Inc.