Electrophysiological evidence for the autoregulation of β-cell secretion by insulin

Electrophysiological studies of cultured rat pancreatic β-cells using intracellular microelectrodes show that exogenous insulin over the range of 0.1–10.0 μg/ml inhibits the electrical activity due to 27.8 mM glucose in a dose-related manner. This inhibitory effect is manifested by a mean increase of the membrane potential from about ?20 to ?30 mV and inhibition of the manner of cells impaled showing spike activity from 60 to less than 10%. The inhibitory influence of insulin is rapid occuring within 5 min for the highest level used. The results provide evidence for a negative feedback role of insulin in regulating its own release.     

Mold colonization during use of preservative-treated and untreated air filters, including HEPA filters from hospitals and commercial locations over an 8-year period (1996–2003)

High efficiency particulate arrestance (HEPA; 99.97% efficient at 0.3 m) filters, filters with ASHRAE particulate arrestance rating of 90–95% at 1 m (90–95% filters), and lower efficiency cellulosic-polyester filters from air conditioning systems in hospitals and commercial buildings were removed from the systems and examined microscopically for mold colonization. Cellulosic-type filters from systems with water entrainment problems typically were colonized, or became colonized upon incubation in moisture chambers. Species of Acremonium, Aspergillus, and Cladosporium were most common. With air filters of all types, treatment of filter media with an antimicrobial preservative tended to reduce or delay colonization. Mold colonization of HEPA and 90–95% filters was observed most often on the load surfaces, but two untreated HEPA filters were permeated with fungi, one with Aspergillus flavus, the other with Cladosporium sp. Air filters in heating, ventilating, and air conditioning (HVAC) systems, particularly those with chronic or periodic exposure to moisture, may serve as point sources for indoor molds.     

Cold storage preservation of islet and pancreas grafts as assessed by in vivo function after transplantation to diabetic hosts

The major goal of hypothermic (4–8 °C) preservation of intact pancreases or isolated islets will be to provide sufficient time for HLA typing, cross matching, selection, and preparation of recipients—logistical efforts requiring 12–72 hr for clinical kidney transplantation, usually <48 hours. Some investigators have studied in vitro function of islets after cold storage, but the critical test of viability—permanent restoration of normoglycemia after transplantation to diabetic recipients—has been tested in only a few experiments. Reversal of hyperglycemia by syngeneic or autogenic transplants in diabetic animals has been achieved after CS of dispersed pancreatic tissue from neonatal rats in GIB media for ? 146 hr, adult dogs in TCM 199 for ?24 hr, and adult DL-ethionine-treated rats in RPMI 1640 for ?72 hr. In the neonatal rat donor model, intravenous glucose tolerance test (IVGTT) results were similar in recipients of fresh or stored islets; in the dog model, IVGTT test results were variable, but generally inferior in recipients of stored as compared to fresh islets; in the adult rat donor model, recipients of ?24-hr coldstorage islets had insulin and IVGTT K values similar to those of recipients of fresh islets, but the success rate progressively declined for CS times >24 hr. Various agents were added to the media, but the need or the optimal concentrations were not critically determined by using different recipes for different groups of recipients. Cold storage of intact pancreas autografts has been tested in dogs; simple electrolyte solutions are satisfactory for 24 hr, but only a silica gel-filtered plasma-based solution has been reliable for 48 hr. Pulsatile machine perfusion (PMP) of canine pancreas grafts for 24 hr has had a success rate similar to CS in some experiments and lower in others. PMP has been almost totally unreliable for >24 hr. Further refinements are needed if preservation of islets for >24 hr and pancreases for >48 hr are to be consistently successful. If current experimental techniques are effective for human islets or pancreases, however, these times are sufficient to complete the logistical maneuvers required before transplantation.     

Quantitation of epinephrine- and glucagon-sensitive adenylate cyclases of rat liver implications of alterations of enzymatic activities during preparation of particulate fractions and membranes

Stimulated and basal adenylate cyclase activities from livers of young and old rats were lower in particulates than in homogenates. Particulates were compared to homogenates by reconstituting the suspensions to the volume of the homogenates from which they were derived; enzyme activities in paired homogenates and particulates therefore reflected the same amounts of membrane-bound enzyme. The magnitude of the losses of hormone-sensitive activities in particulates was dependent on the age and sex of the animals and the concentrations of hormone. Particulates from 3-month-old animals showed glucagon-( (1 · 10^?5 M) and epinephrine-sensitive (1 · 10^?4 M) activities which were 67 and 78% of homogenate activities, respectively; particulates from 24-month-old animals had activities relative to homogenates of 55% for glucagon and as low as 32% for epinephrine. The glucagon dose vs. response curve in particulates and membranes showed maximal activity at 1 · 10^?7 M glucagon while in homogenates activity increased linearly with increasing glucagon concentrations up to 1 · 10^?5 M. Losses of basal and anion-stimulated activities were similar at both ages. Fluoride and azide stimulations relative to basal activities were greater in particulates than in homogenates, while relative epinephrine activity was lower in particulates, suggesting qualitative alteration of adenylate cyclase during preparation of particulates. These studies show that adenylate cyclase activity in rat liver is presently best quantitated in homogenates and suggest caution in comparisons of enzyme activities based on particulates or membranes prepared from animals of differing physiologic states.     

Specifically induced suppression of T cell and NK-like cytolytic activity by ingested soluble antigens

The effect of feeding xenoserum (xs) on cytolytic cell activity induced by parenteral injection was examined in C3H/N mice. Spleen cells were cultured with xs and then assayed for cytolytic activity against a panel of 51Cr-labeled YAC-1, AKR-A, or P815 target cells. Prior feeding resulted in significant suppression of responses stimulated by injection and culture. The induction of these responses was antigen specific for xs whereas the effector stage represented polyclonal activation of cytolytic cells. Some effector cells were lysed by either anti-Lyt 2 or anti-NK- 1.2 and complement and some were blocked by anti-Lyt 2 or anti-T200 in the cytotoxicity assay. Thus, both cytolytic T and NK-like cells were suppressed by antigen feeding. Activity of TH cell-derived factors which enhance cytolytic activity ("promoter" factor, interferon, and interleukin 2) also was diminished in culture supernatants of cells from mice fed soluble antigens. The conclusion that polyclonal cytolytic responses induced by soluble antigen can be regulated by prior enteric stimulation is made.     

Separation and partial characterization of multiple forms of rat liver alcohol dehydrogenase

Rat liver alcohol dehydrogenase was purified and four isoenzyme forms, demonstrated by starch gel electrophoresis, were separated by O-(carboxymethyl)-cellulose chromatography. Each of the isoenzymes had a distinct isoelectric point. All isoenzymes were active with both ethanol (or acetaldehyde) and steroid substrates, and had similar Michaelis-Menten constants for each of the substrates and coenzymes studied. The three isoenzymes with the lowest migration toward the cathode exhibited the same pH optimum of 10.7 for ethanol oxidation, a greater activity with 5 beta-androstan-3 beta-ol-17-one than with ethanol as a substrate, and an unchanged electrophoretic mobility following storage in the presence of 100 microM dithiothreitol. By contrast the isoenzyme with the highest mobility toward the cathode exhibited a pH optimum of 9.5 for ethanol oxidation, a low steroid/ethanol ratio of activity, and converted to the migrating pattern of the two isoenzymes with intermediate mobility when stored. The similarities between the isoenzymes of rat liver alcohol dehydrogenase differ considerably from differences in substrate specificity exhibited by isoenzymes of horse liver alcohol dehydrogenase.     

Interleukin 1 secretion is not required for human macrophage support of T-cell proliferation

Interleukin 1 (IL-1) is a soluble factor secreted by stimulated monocytes (Mo) and animal macrophages (Mx). We have previously demonstrated that human Mo cultured in vitro for 1-6 days transform to Mx, and retain their ability to support concanavalin A (Con A)-driven T-cell proliferation. We have also shown that, paradoxically, these Mx do not secrete IL-1, when stimulated by endotoxin (LPS). In this study we examined two alternative hypotheses: T cells plus mitogen induce Mx IL-1 production, and human Mx deliver a second signal to T cells via a non-IL-1 mechanism. IL-1 was assayed in a mouse CD-1 thymocyte system without concanavalin A. Mo/Mx were cultured with T cells at low (2 X 10(4)/200 microliters) or high (1 X 10(5)/200 microliters) concentrations for 2 or 4 days, in the presence of Con A. Six hours prior to quantitation of proliferation, 50 microliters of supernatant was removed and assayed for IL-1. As expected both Mo and Mx enhanced T-cell proliferation eight- to tenfold. Mo secreted large amounts of IL-1; there was no demonstrable IL-1 activity present in supernatants from cultures containing either T cells and Mx, or Mx alone. Similar results were obtained by preincubating the cells (Mo, Mx, and T cells) with Con A for 12 hr and removing Con A prior to a 36-hr coculture. We examined the possibility that a small amount of IL-1 may be able to support Con A-stimulated T-cell proliferation and yet may not induce thymocyte proliferation. The highest dilutions of Mo supernatant (1:125) which supported T-cell proliferation also caused a fivefold increase in thymocyte proliferation. Supernatants from Mx failed to stimulate thymocyte proliferation or support Con A-driven T-cell proliferation. However, Mo and Mx lysates contain Il-1 activity. We conclude that human Mx support Con A-induced T-cell proliferation in the absence of IL-1 secretion. Mx may support T-cell proliferation by cell-bound IL-1 or by a non-IL-1 mechanism.     

Antigen-induced in vitro lymphocyte blastogenesis in the rabbit: a T-cell response.

In vitro lymphocyte stimulation of sensitized rabbit lymphocytes to specific antigen (ovalbumin) was found to depend on thymic-dependent lymphocytes. This conclusion is based on an enhanced response upon enrichment with T lymphocytes by passage of lymphocytes through nylon wool, and on the elimination of the response after treatment of lymphocytes with complement and an antiserum to rabbit thymus cells prepared in a goat. Specificity of the antiserum was demonstrated by elimination of in vitro T-cell function and retention of in vitro B-cell functions.     

Cancer diagnostic delays and travel distance to health services: A nationwide cohort study in Denmark

BackgroundThis study aims to investigate the association between distance to health services and intervals in the cancer diagnostic pathway, and explore whether the diagnostic difficulty of the cancer influences this association.MethodA nationwide cohort study was conducted based on data from both questionnaires and registries. Danish cancer patients diagnosed in 2005–2016 and their general practitioner (GP) were included if enrolled in the Danish Cancer in Primary Care (CaP) cohort (n = 37,872). The CaP cohorts provided data on intervals assessed by patients and GPs. The Geographical Information System (GIS) was used to calculate travel distances from the residence of the patient to their GP surgery and to the hospital of diagnosis.ResultsLonger travel distance to the hospital of diagnosis was associated with longer diagnostic interval. This association was strongest in the period before the implementation of Cancer Patient Pathways (CPP) in 2010. Patients with a cancer categorised as ´hard to diagnose´ contributed mostly to the association. Longer travel distance to the GP was associated with shorter patient interval and primary care interval for patients diagnosed with cancer types ´intermediate to diagnose´.ConclusionTravel distance to cancer diagnostic health care services was associated with interval length in the diagnostic pathway. This association was less pronounced in the period after introducing CPPs and also strongly depending of the underlying cancer type and symptomatology.