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Biomedical subjects

D Goode

Publications and source records attributed to D Goode.

At least 37 records · Page 2Linked to original sources
PubMed1994

Effects of the microtubule depolymerizing and stabilizing agents Nocodazole and taxol on glucose-induced insulin secretion from hamster islet tumor (HIT) cells.

Hamster islet tumor (HIT) cells retain much of the capacity of normal beta cells to act as glucose sensors. When stimulated with glucose or glucose plus forskolin, HIT cells release much more insulin than unstimulated cells. Ultrastructural analysis reveals that the secretory product of these cells is stored in membrane-bound granules that associate with microtubules under certain circumstances. Immunofluorescence studies using insulin antibody confirm the presence of insulin in granular structures in these cells. The microtubule inhibitor Nocodazole reduces the number of polymerized microtubules and inhibits the sustained phase of insulin secretion in HIT cells. Thus, the structural integrity of microtubules is important for the sustained phase of the insulin secretion to occur. The microtubule stabilizing drug taxol does not decrease insulin secretion. Since taxol blocks microtubule depolymerization, microtubule polymerization-depolymerization alone does not appear to be responsible for insulin granule transport. The increased use of these drugs in cancer research and therapy makes it important to understand their effects on insulin secretion.

Adenoma, Islet Cell↗
PubMed1991

Nonlinear steady-state kinetics of chloramphenicol acetyltransferase.

Steady-state kinetic analysis of chloramphenicol acetyltransferase showed that medium effects (higher temperatures or pH, higher ionic strengths, or lower values for dielectric constant) altered the kinetic behaviour of the enzyme with acetyl-CoA as substrate, but did not significantly affect behaviour with chloramphenicol. This was manifest as an increase in the degree of the rate equation to a 2:2 function. This is interpreted in terms of perturbations to the enzyme at or near the acetyl-CoA binding region of the enzyme.

Acetyl Coenzyme A↗
PubMed1990

Lysine vasopressin in the treatment of refractory hemodialysis-induced hypotension.

The etiology of hemodialysis-induced hypotension is multifactorial. We assessed the efficacy of intranasal lysine vasopressin (LV) in 6 patients with refractory hemodialysis-induced hypotension. Autonomic testing was abnormal in all. Intranasal LV and placebo were assessed in a double-blind crossover fashion. With LV, the mean number of hypotensive episodes was less (0.9 +/- 0.8 vs. 1.5 +/- 1; t = 3.95, p less than 0.05), as was the total volume of intravenous fluid administered because of hypotension (155 +/- 57 vs. 280 +/- 123 cm3; t = 2.98, p less than 0.05). Systolic, diastolic, and mean arterial blood pressures were significantly greater at 90 min of the dialysis session. Measured baseline epinephrine, norepinephrine, and antidiuretic hormone levels were elevated above normal levels and fell with hypotension despite the use of LV. The results from this study demonstrate the utility of LV in the treatment of refractory hemodialysis-induced hypotension.

Administration, Intranasal↗
PubMed1986

Incorporation and turnover of labeled exogenous tubulin in the mitotic spindles of Chaetopterus oocytes and HeLa cells.

The incorporation of tubulin into mitotic spindles in situ was studied by incubating permeabilized mitotic cells in solutions containing [3H]GTP-labeled or dichlorotriazinylamino fluorescein (DTAF)-labeled tubulin. Metaphase HeLa cells or spindle-containing "minicells" from Chaetopterus oocytes were lysed in a microtubule-assembly buffer plus 0.5% Nonidet P-40, 1 mg/ml 120,000g supernatant mammalian brain tubulin, and [3H]GTP. After different periods of incubation, mitotic spindles were isolated in 2 M-glycerol-containing assembly buffer and separated from unbound counts by centrifugation through a 4 M-glycerol cushion; 3H counts per mg protein increase linearly for 8-12 min and then reach a plateau or steady state in both Chaetopterus oocytes and HeLa cells. Addition of 4 mM CaCl2 blocks or reverses incorporation. Little or no [3H]GTP is incorporated if exogenous tubulin or lysed cells are omitted from the assembly mixture. To measure the loss rate of [3H]GTP-tubulin from mitotic spindles, cells were incubated in tubulin plus [3H]GTP for 30 min, and a 20-fold excess of cold GTP (2 mM) was added. Samples were removed after incubation for different periods, and spindles were isolated as described above and counted for 3H content. [3H]GTP is lost from spindles at a rate of about 16%/min until a new steady state is reached in about 8 min. These results are consistent with an incorporation and turnover of [3H]GTP-tubulin in spindle microtubules of these lysed-cell models. The location of this newly incorporated tubulin in the spindle was investigated by incorporating fluorescent DTAF-tubulin into mitotic spindles of these lysed cell types.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Bacteriophage typing of strains of Mycobacterium tuberculosis from Nepal.

One hundred strains of Mycobacterium tuberculosis isolated from cases of pulmonary tuberculosis in Nepalese villagers were typed with the World Health Organization set of bacteriophages. The number of strains in the 3 major phage types A, I, and B were 19, 53, and 28 respectively. This distribution is significantly different from those described in other geographical regions. In particular there was a relatively low incidence of type A strains and, in common with South India, there was a high proportion of type I strains. All the strains in this study were resistant to 5-Furan-2 carbonic acid hydrazine and 34 were highly resistant to isoniazid. Representative strains of the 3 phage types, including 4 isoniazid-resistant type I strains, did not differ in their virulence in the guinea pig; thus the type I strains found in Nepal may not be of the same origin as those of this phage type from India which are usually attenuated in the guinea pig. This study provides further evidence for the existence of geographical differences in the types of tubercle bacilli.

Animals↗
PubMed1981

Microtubule turnover as a mechanism of mitosis and its possible evolution.

Movement of chromosomes during mitosis appears to be coupled to the unidirectional turnover of spindle microtubules. This paper outlines a directional turnover model of mitosis which hypothesizes that: (1) Unidirectional turnover of tubulin subunits and microtubule-associated proteins occurs from an assembly site at one end to a disassembly site at the other end of mitotic apparatus microtubules. (2) The components of interpolar microtubules are continuously moving toward each pole due to their assembly in the opposite half spindle and disassembly in the near half spindle. (3) Mitotic chromosome movements are coupled to this directional turnover by selective formation of semi-stable lateral interactions or bridges between kinetochore microtubules and parallel interpolar microtubules. (4) The anaphase velocity of kinetochores relative to the poles is determined by the rate that kinetochore microtubules disassemble on their poleward ends minus the rate they assemble at their kinetochore ends. (5) Spindle elongation occurs when assembly of interpolar microtubules is more rapid than their disassembly or when interpolar microtubules slide in an anti-parallel arrangement. (6) The velocity of chromosome separation is the sum of spindle elongation and the poleward movements of sister chromosomes. Evidence for and against these hypotheses and some possible steps in the evolution of this type of mechanism are discussed.

Animals↗
PubMed1979

Stimulation of human chorionic gonadotropin by JAr line choriocarcinoma after inhibition of DNA synthesis.

Treatment of choriocarcinoma cells (JAr line) for 24 hr with methotrexate, fluorodeoxyuridine, 1-beta-D-arabinofuranosylcytosine, or hydroxyurea, in doses that inhibit DNA synthesis, results in a 2.5- to 12-fold increase in human chorionic gonadotropin (HCG) synthesis. Under the conditions of use, these agents do not significantly depress RNA or protein synthesis. Simultaneous addition of thymidine with methotrexate or fluorodeoxyuridine and of deoxycytidine with 1-beta-D-arabinofuranosylcytosine blocks the HCG stimulation. Despite a rapid inhibition of DNA synthesis, HCG stimulation is gradual and reaches a peak after drug removal. Decline in HCG synthesis is coincident with recovery of DNA synthesis, and there is a positive correlation between the duration of inhibition of DNA synthesis and the amount of HCG increase. Although most of the methotrexate-induced stimulation of HCG synthesis occurs after methotrexate removal, preventing protein synthesis during the exposure to methotrexate abrogates the increase. The stimulation of HCG synthesis by methotrexate is more sensitive to protein synthesis inhibition during the first 12 hr of a 24-hr exposure than it is during the second 12 hr. Thus, in accord with the kinetics, specificity, dose dependence, and protein synthesis requirement, HCG synthesis seems to be stimulated as a direct consequence of inhibition of DNA synthesis, with a requirement for some other protein synthesis-dependent event(s) preceding the stimulation.

Cell Line↗
PubMed1977

Ca+2-accumulating components in developing skeletal muscle.

This ultrastructural study on the localization of Ca+2 in developing skeletal muscle indicates that the formation of calcium-accumulating components begins during embryonic development. Both oxalate and pyroantimonate techniques are used to localize Ca+2 in distinct cellular components of chick pectoral and sartorius muscles. Two major sites for Ca+2 accumulation are present in ultrathin sections of embryonic and post-embryonic muscles: the terminal cisternae of the sarcoplasmic reticulum and specific lines in the I-bands. Calcium oxalate-accumulating vesicles are present in the smallest recognizable myotubes at the twelfth day of incubation, but calcium-accumulating components are not seen at myofibrillar I-band sites until the fourteenth to seventeenth days of incubation. The fact that myofibrils first form and later in development accumulate a Ca+2-binding component suggests that this Ca+2-binding component is not necessary for the formation of myofibrils, but is added to myofibrils before hatching to serve a probable regulatory role in contraction.

Age Factors↗
PubMed1976

Effect of incubation in human plasma on electrophoretic mobility of brain-type creatine phosphokinase.

1. Electrophoretic mobility of brain-type creatine phosphokinase (CPK) from rabbit, rat and human decreased after incubation in human plasma for 3 h or 17 h but did not change after incubation in isotonic saline solution. The presence of the reducing agent mercaptoethanol during incubation in human plasma tended to reduce the rate of change of electrophoretic mobility of BB-CPK. 2. The activity of brain CPK was almost completely lost after incubation for 17 h in human plasma. The addition of mercaptoethanol after incubation of brain CPK in human plasma could only partially restore the enzyme activity. 3. The decrease in electrophoretic mobility of rat brain CPK occurred after incubation in an ultra-filtrate of human plasma which contained molecules whose molecular weight did not exceed 1000. 4. Gel chromatography indicated that incubation of brain CPK in human plasma did not markedly change the molecular size of the enzyme.

Animals↗
PubMed1976

Pressure-induced depolymerization of spindle microtubules. III. Differential stability in HeLa cells.

Evidence from light microscopy (principally polarization microscopy) has demonstrated that hydrostatic pressure can reversibly inhibit mitosis by rapidly depolymerizing the spindle fiber microtubules. We have confirmed this finding in ultrastructural studies of mitotic HeLa cells incubated at 37 degrees C and pressurized at 680 atm (10,000 psi). Althouth there are many spindle microtubules in the cells at atmospheric pressure, electron micographs of cells pressurized for 10 min (and fixed while under pressure in a Landau-Thibodeau chamber) show few microtubules. Pressure has a differential effect on the various types of spindle microtubules. Astral and interpolar MTs appear to be completely depolymerized in pressurized cells, but occasional groups of kinetochore fiber microtubules are seen. Surprisingly, the length and density of microtubules of the stem bodies and midbody of telophase cells appear unchanged by pressurization. In cells fixed 10 min after pressure was released, microtubules were again abundant, the density often appearing to be higher than in control cells. Reorganization seems incomplete, however, since many of the microtubules are randomly oriented. Unexpectedly, kinetochores appeared diffuse and were difficult to identify in sections of pressurized cells. Even after 10 min of recovery at atmospheric pressure, their structure was less distinct than in unpressurized cells.

Chromosomes↗