The role of hypoxia in the maintenance of hematopoietic stem cells

Bone marrow cell liquid cultures were incubated at various oxygen concentrations ranging from 0% to 18% (air). The total number of cells in culture (CT) at the end of a 6-day incubation was found to be directly proportional to the oxygen concentration. As compared with air- incubated controls, cells recovered from severely hypoxic (1% oxygen) day-5 liquid cultures showed (1) the same day-7 colony-formation efficiency in semisolid culture (neutrophilic/monocytic colonies) or in spleen; (2) a higher day-14 spleen colony-formation efficiency; (3) an enhanced radio-protection ability; and (4) an increased marrow repopulation ability, as measured by determining either total cell number in recipient marrow MRAcell, or the capacity of the latter of generating day-7 neutrophilic/monocytic colonies in secondary in vitro assays (MRACFU-NM). Taking into account CT, the absolute numbers of progenitors in culture were also computed. The results showed that, with respect to time 0, incubation in air produced an increase in the number of day-7 CFUs and a decrease in the number of the other progenitors, whereas in hypoxic cultures all types of progenitors decreased. However, as compared with air-incubated controls, all progenitors, except cells sustaining MRACFU-NM, were reduced in hypoxic cultures. The degree of reduction paralleled the position of the progenitor in the hematopoietic hierarchy, being maximum for day-7 CFUs and null for cells sustaining MRACFU-NM, which, in fact, were better preserved in hypoxic cultures.     

Capillaries and flow redistribution play an important role in muscle blood flow reserve capacity

Perfusion of skeletal muscle varies considerably during rest, exercise, or when arteries are occluded. The extent that a muscle can adapt to changes in flow demand is often expressed as the ratio of the highest inducible flow and control flow, the microvascular blood flow reserve capacity (MBFRC). However, perfusion of the nutritive capillaries of skeletal muscle may not only be improved by the increase in blood flow proportional to the increase in arterial flow, but also by diverting originally shunted flow towards the muscle proper. Consequently, MBFRC is not a good measure of capillary flow reserve, unless the assessed flow in both conditions is purely nutritive in nature. Therefore, in critical conditions, flow measurements in large vessels are not appropriate to assess MBFRC. In muscle, capillaries are compliant, i.e., with varying transmural pressure capillary diameter varies. During high perfusion states, when capillary transmural pressure is increased, capillary compliance results in increased capillary diameter and, hence, in reduced resistance and increased exchange surface area. This results in improved perfusion and enlarged capillary exchange surface area. In low perfusion states, capillary diameter is reduced. This augments the detrimental effects of the low perfusion status. Operative restoration of perfusion pressure not only increases the driving force for perfusion, but also leads to (passive) dilatation of the capillary bed and an extra reduction in resistance to flow, and, hence, a disproportional increase in flow.     

Characterization of the serum In(Lu)-related antigen: identification of a serum protein related to erythrocyte p80

The In(Lu) gene has been shown previously to downregulate expression by erythrocytes and by a subset of leukocytes of an 80-Kd protein antigen defined by monoclonal antibody (MoAb) A3D8. A3D8 antibody has also been shown by inhibition studies to recognize a serum antigen; this serum antigen is present in reduced amount in serum from In(Lu) donors. The present study demonstrates that the serum antigen recognized by A3D8 antibody also resides on a protein similar in size to the protein present in erythrocyte membranes. Studies using chromatographically purified protein have further shown that this antigen shares many epitopes with that present in RBCs and is therefore likely to be extremely homologous or identical to the erythrocyte In(Lu)-related p80.     

Velocity profiles of blood platelets and red blood cells flowing in arterioles of the rabbit mesentery

Velocity profiles were determined in rabbit mesenteric arterioles (diameter 17-32 micron). A good spatial resolution was obtained by using the blood platelets as small and natural markers of flow, providing for the first time in vivo detailed, quantitative information about the shape of the velocity profiles in microvessels. In some experiments red blood cell velocity profiles were recorded as well. Easy detection of the cells of interest could be achieved by labelling them selectively with a fluorescent dye and visualizing them by intravital fluorescence video microscopy, using flashed illumination. Pairs of flashes were given with a short, preset time interval between both flashes, yielding in one TV picture two images of the same cell displaced over a certain distance for the given time interval. Velocity and mean radial position of cells, flowing within an optical section around the median plane of the vessel, were determined. The shape of the velocity profiles of platelets and red blood cells was similar. The profiles were flattened as compared to a parabola, both in systole and diastole. Vessel diameter did not change measurably during the cardiac cycle. As an index of the degree of blunting of the profiles, the ratio of the maximal and mean velocity of the profile was used, which is 2 for a parabola and 1 for complete plug flow. The index ranged from 1.39 to 1.54 (median 1.50), and increased with vessel diameter. Calculations showed that the blunting of the profiles cannot be explained by an influence of the finite depth of the optical section.     

Fractures in the maxillofacial region: A four year retrospective study

Introduction: The incidence of maxillofacial injuries is on the rise due to motor vehicle accidents and increased incidence of violence in recent times. The aim of this retrospective study was to determine the incidence, aetiology, the pattern of fractures, their management with open reduction and internal fixation (ORIF) and complications, if any.     

Intra‐abdominal vacuum‐assisted closure (VAC) after necrosectomy for acute necrotising pancreatitis: preliminary experience

Infection of pancreatic necrosis, although present in less than 10% of acute pancreatitis, carries a high risk of mortality; debridment and drainage of necrosis is the treatment of choice, followed by ‘open’ or ‘close’ abdomen management. We recently introduced the use of intra‐abdominal vacuum sealing after a classic necrosectomy and laparostomy. Two patients admitted to ICU for respiratory insufficiency and a diagnosis of severe acute pancreatitis developed pancreatic necrosis and were treated by necrosectomy, lesser sac marsupialisation and posterior lumbotomic opening. Both of the patients recovered from pancreatitis and a good healing of laparostomic wounds was obtained with the use of the VAC system. Most relevant advantages of this technique seem to be: the prevention of abdominal compartment syndrome, the simplified nursing of patients and the reduction of time to definitive abdominal closure.     

Effects of nitric oxide on neutrophil influx depends on the tissue: role of leukotriene B4 and adhesion molecules

Background and purpose:

We investigated the effect of nitric oxide synthase (NOS) inhibition on polymorphonuclear cell (PMN) influx in zymosan or lipopolysaccharide (LPS)-induced arthritis and peritonitis.

Experimental approach:

Wistar rats received intra-articular (i.art.) zymosan (30–1000 µg) or LPS (1–10 µg). Swiss C57/Bl6 mice genetically deficient in intercellular adhesion molecule-1 (ICAM-1^−/−) or in β₂-integrin (β₂-integrin^−/−) received zymosan either i.art. or i.p. PMN counts, leukotriene B₄ (LTB₄), tumour necrosis factor-α (TNF-α) and interleukin-10 (IL-10) levels were measured in joint and peritoneal exudates. Groups received the NOS inhibitors N^G-nitro-L-arginine methyl ester (LN), nitro-L-arginine, N-[3-(aminomemethyl)benzyl] acetamide or aminoguanidine, prior to zymosan or LPS, given i.p. or s.c. in the arthritis and peritonitis experiments respectively. A group of rats received LN locally (i.art. or i.p.), 30 min prior to 1 mg zymosan i.art.

Key results:

Systemic or local NOS inhibition significantly prevented PMN migration in arthritis while increasing it in peritonitis, regardless of stimuli, concentration of NOS inhibitors and species. NOS inhibition did not alter TNF-α and IL-10 but decreased LTB₄ in zymosan-induced arthritis. LN administration significantly inhibited PMN influx into the joints of ICAM-1^−/− and β₂-integrin^−/− mice with zymosan-arthritis, while not altering PMN influx into the peritoneum of mice with zymosan-peritonitis.

Conclusions and implications:

Nitric oxide has a dual modulatory role on PMN influx into joint and peritoneal cavities that is stimulus- and species-independent. Differences in local release of LTB₄ and in expression of ICAM-1 and β₂-integrin account for this dual role of NO on PMN migration.