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Biomedical subjects

C R Benedict

Publications and source records attributed to C R Benedict.

At least 145 records · Page 8Linked to original sources
PubMed1968

Characteristics of a virescent cotton mutant.

The virescent cotton (Gossypium hirsutum) mutant described here differs from normal cultivated cotton by a single mutation in the nucleus. The mutant exhibits nuclear control of chlorophyll and carotenoid development. Young leaves are distinctly yellow and become green with age. There is no unusual photometabolism of (14)CO(2) or (14)C-acetate in this mutant. It is probable that the nuclear virescent mutation is in a locus concerned with making structural units. The yellow leaves do show a high photosynthetic capacity on a chlorophyll basis. At saturating light intensity the rate of CO(2) fixation is 8 fold higher than the green control leaves. Thus, impaired pigment synthesis which could be lethal is offset by a high photosynthetic capacity in the virescent leaves.

Journal Article↗
PubMed1968

PEP carboxykinase exchange reaction in photosynthetic bacteria.

This paper describes some new characteristics of the phosphoenolpyruvate carboxykinase CO(2)-oxaloacetate exchange reaction in purified preparations of Rhodospirillum rubrum. The enzymatic activity has been purified 169-fold. Nucleotide diphosphates substitute for nucleotide triphosphates in the exchange reaction. Nucleotide diphosphates will not support the synthesis of phosphoenolpyruvate from oxaloacetate. This reaction differs significantly from the CO(2)-oxaloacetate exchange reaction in higher plants and animals.

Pyruvate Kinase↗
PubMed1967

Mevalonic acid kinase in Euglena gracilis.

The isolation and partial purification of mevalonic acid kinase from Euglena gracilis is described. The product of the reaction MVA-5-P has been characterized by paper chromatography. The apparent Km values for l-mevalonic acid, ATP, and Mg(2+) are 3 x 10(-5)m, 6 x 10(-3)m, and 9 x 10(-3)m, respectively. A concentration of 1 x 10(-3)mp-hydroxymercuribenzoate completely inactivates the enzyme. A distribution study has shown that mevalonic acid kinase is present in most higher plants and the algae Euglena gracilis and Chlamydomonas. No enzymatic activity could be detected in several species of photosynthetic bacteria or blue-green algae.

Adenosine Triphosphate↗
PubMedDate not supplied

Microcomputer-based analysis of cardiovascular indices.

A microcomputer-based program has been developed which performs rapid and accurate acquisition of cardiovascular data from instrumented animals or isolated perfused hearts with concurrent analysis and display of the hemodynamic indices. The system allows real-time viewing of the data in four alternative graphic displays. These include: (1) a strip-charge type display of all channels; (2) a full screen display of any single channel; (3) display of pressure-segment length; and (4) trend graphs (cumulative change with time) of calculated hemodynamic indices such as heart rate, systolic and diastolic blood pressure, percent change in myocardial segment length, mean blood flow and percent change in arterial diameter. Precise analysis of both transient and steady-state events may be performed on any segment of data stored on the hard disk. The data at any point in the experiment may be accessed by cursoring through any trend graph of the derived indices, by recalling special event markers or by using the automatic time markers. The calculated results are printed and stored in ASCII files which can be transferred to spreadsheets, databases, graphics or statistical programs.

Animals↗
PubMedDate not supplied

Differential induction of 3-hydroxy-3-methylglutaryl CoA reductase in two cotton species following inoculation with Verticillium.

Gossypium barbadense cottons are typically more resistant to wilt pathogens than are Gossypium hirsutum cultivars. Both species make terpenoid phytoalexins in response to infection, implicating isoprenoid biosynthesis as a factor in resistance. Conserved regions in plant 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), the first enzyme in the terpene biosynthesis pathway, were used to design polymerase chain reaction primers for cloning a fragment of a cotton HMGR gene. The clone was used as a probe on Northern blots to show that induction of HMGR mRNA following introduction of Verticillium dahliae spores into the vascular system is much more rapid in Seabrook Sea Island, a restant G. barbadense cotton, than it is in Rowden, a susceptible G. hirsutum. The amount of HMGR mRNA returned to near control levels in 4 days in the former variety but continued to accumulate in the latter. Specific enzyme activity of HMGR also increased more rapidly in stele extracts of Seabrook Sea Island than in Rowden.

Amino Acid Sequence↗
PubMedDate not supplied

Monocyte chemotactic protein 1 amplifies serotonin-induced vascular smooth muscle cell proliferation.

Monocyte chemotactic protein 1 (MCP-1), which is synthesized by vascular cells, is a chemoattractant for monocytes and has been implicated in a wide range of acute and chronic inflammatory processes characterized by monocyte infiltration, including atherosclerosis. However, it is unclear whether MCP-1 is able to modulate vascular smooth muscle cell (VSMC) proliferation. We assessed the effect of MCP-1 on VSMC proliferation and its interaction with serotonin (5-HT), a mitogen for VSMCs. Growth-arrested VSMCs were stimulated with different concentrations of MCP-1 (25-200 ng/ml) and 5-HT (5 and 50 microM) in serum-free medium. DNA synthesis in VSMCs was measured by [3H]thymidine incorporation. 5-HT at concentrations of 5 and 50 microM significantly stimulated DNA synthesis by 1.8- and 2.1-fold over the control value, respectively (p < 0.0001). However, MCP-1 at the concentrations tested did not have any significant effect on DNA synthesis. Even though MCP-1 (50 ng/ml) by itself is not mitogenic, when added to 5-HT, it significantly amplified the mitogenic effect of 5-HT compared with that of 5-HT alone (p < 0.0001). The 5-HT2A receptor antagonist sarpogrelate (10 microM) and its major metabolite M-1 (0.1 microM), pertussis toxin (10 ng/ml), Src family protein tyrosine kinase (PTK) inhibitor PP2 (1 microM), protein kinase C (PKC) inhibitor Ro31-8220 (0.1 microM) and mitogen-activated protein kinase (MAPK) kinase inhibitor PD098059 (10 microM) significantly inhibited the mitogenic effect of 5-HT and its interaction with MCP-1. Anti-MCP-1 antibody (2 microg/ml) and the Janus kinase 2 (JAK2) inhibitor AG490 (10 microM) significantly inhibited the interaction of MCP-1 with 5-HT. Further, the amplified mitogenic effect of 5-HT with MCP-1 was completely reversed by the combined use of sarpogrelate with anti-MCP-1 antibody. Our results suggest that MCP-1 amplifies the mitogenic effect of 5-HT on VSMCs. The mitogenic effect of 5-HT may be mediated by the G protein-Src family PTK-PKC-MAPK pathway. The activation of the JAK2/signal transducer and activator of transcription 3 pathway by MCP-1 in addition to the MAPK pathway by 5-HT may explain the potentiating effect of MCP-1 on 5-HT-induced mitogenesis.

Animals↗
PubMedDate not supplied

Chronic dietary tyrosine supplements do not affect mild essential hypertension.

The blood pressure and plasma norepinephrine response to oral tyrosine, the precursor of norepinephrine, supplementation (2.5 g t.i.d.) of regular meals was examined in 13 untreated patients with mild essential hypertension. Using a randomized double-blind crossover design, each 2-week treatment was followed by a 2-week supplement-free interval. Supine and standing blood pressure and plasma norepinephrine levels were measured at the beginning and end of each 2-week treatment. Plasma tyrosine levels increased (p less than 0.001) from 71.2 +/- 8.0 nM/ml at baseline to 152.8 +/- 17.4 nM/ml 2 hours after the tyrosine supplement. Blood pressure under control conditions was 144 +/- 3 Hg systolic, 91 +/- 2 mm Hg diastolic (109 +/- 2 mm Hg mean) after 30 minutes in the supine position and 148 +/- 4 mm Hg systolic, 102 +/- 3 mm Hg diastolic (117 +/- 3 mm Hg mean) after 5 minutes of standing. Plasma norepinephrine levels were 191 +/- 18 pg/ml in the supine subjects and 390 +/- 33 pg/ml in the standing subjects. No difference in systolic, diastolic, or mean blood pressure, heart rate, or plasma norepinephrine levels were seen between the beginning and end of each period or between groups. Individual changes in blood pressure showed no correlation with individual changes in norepinephrine levels. These results indicate that the addition of a tyrosine supplement to the usual diet of mild hypertensive subjects has no beneficial effect on blood pressure.

Administration, Oral↗
PubMedDate not supplied

Sympathetic nervous system activity in patients with subarachnoid hemorrhage.

In patients with subarachnoid hemorrhage there were increased concentrations of plasma epinephrine and norepinephrine when compared with those concentrations in a group of patients admitted to hospital with other illness. Reassessment after a variable period showed that in patients whose eventual clinical result was poor the plasma epinephrine and norepinephrine concentrations increased further while in those with a good result those concentrations showed a decline. No such changes were evident in plasma dopamine-beta-hydroxylase activities which were within normal range. In a sub-group of patients who had neurosurgery after admission for clipping an aneurysm, the post-operative changes of plasma epinephrine and norepinephrine concentrations were related to the clinical condition of the patients.

Adolescent↗