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Biomedical subjects

D H Wallace

Publications and source records attributed to D H Wallace.

54 records · Page 3Linked to original sources
PubMed1979

Effect of Fruits on Dormancy and Abscisic Acid Concentration in the Axillary Buds of Phaseolus vulgaris L.

The mechanism regulating the growth of adult plants in two determinate bean (Phaseolus vulgaris L.) cultivars was investigated. "Redkloud" plants flowered, formed fruits, and ceased shoot growth earlier than "Redkote" plants. Redkloud attained a smaller plant size, compared to Redkote, by imposing dormancy on axillary buds at an earlier age. In both cultivars, cessation of bud growth coincided with maximum combined fruit length per plant. Removal of fruits caused resumption of axillary bud growth within 4 to 5 days. The amount of new growth induced by fruit removal depended on the cultivar and plant age. In fully developed Redkloud plants, where shoot growth had already ceased, total leaf and shoot number per plant nearly doubled within 2 weeks following fruit removal. A much smaller response was observed in the still growing Redkote plants. Fruits, therefore, are assumed to play a major role in the regulation of shoot growth and total plant size through the control of axillary bud dormancy. It seems that smaller plant size, earlier maturity, and earlier senescence of Redkloud, compared to Redkote, were the result of earlier flowering, and accomplished in part through the growth-inhibiting action of fruits.The endogenous abscisic acid (ABA) concentration of axillary buds was higher in Redkloud than in Redkote. It increased with plant age in both cultivars. Five days after fruit removal the ABA level in bud tissue dropped to approximately 10 to 30% of the control level. When buds were treated with a solution of ABA containing 5 nanomoles of ABA per bud, growth was substantially inhibited. Fifteen days after ABA application the mean length of growing buds on intact and defruited plants was reduced by 40 and 62%, respectively, compared to the untreated controls. A role for ABA in axillary bud growth regulation was not firmly established, but these data suggest correlation between the growth potential of axillary buds and their ABA concentration.

Journal Article↗
PubMed1979

Effect of Older Fruits on Abortion and Abscisic Acid Concentration of Younger Fruits in Phaseolus vulgaris L.

In two cultivars of bean (Phaseolus vulgaris L., Redkloud and Redkote) the older fruits growing at the base of racemes aborted less frequently than the younger ones above them. When older fruits at the base of racemes were removed, the abortion rate of the younger ones was reduced and their abscisic acid (ABA) concentration was lowered. Thirteen days after fruit removal, 36 to 45% of the younger fruits remained viable on treated plants while less than 12% of the younger fruits were viable on control plants. On these intact controls the ABA concentration of young fruits was at least twice that of defruited plants. A similar difference was found when the ABA content was expressed on a per fruit basis, suggesting a direct regulatory influence of older fruits over the ABA content of younger fruits.

Journal Article↗
PubMed1977

Sympathetic blockade of isolated limbs by intravenous guanethidine.

As a result of experience at the Montreal General Hospital, it has been found that intravenous guanethidine blockade of extremities has therapeutic, prophylactic and diagnostic value in conditions where the aetiology is a disorder of sympathetic nervous conduction. The properties of guanethidine, namely its selective action on blocking the sympathetic nervous system peripherally, together with its long half time and rapid tissue fixation, render it a very useful drug in techniques where an isolated limb is blocked with guanethidine. Experience on a 18-month basis suggests that the procedure of intravenous guanethidine blockade offers exceptionally good results for a non-invasive technique. Work is now in progress to study the possible use of guanethidine in the treatment of phantom limb pain, and also to see whether other drugs, such as thymoxamine, could be used in a similar fashion to guanethidine.

Anesthesia, Intravenous↗
PubMed1975

The use of the fiberoptic bronchoscope to facilitate endotracheal intubation following head and neck trauma.

The fiberoptic bronchoscope is an invaluable aid in the difficult endotracheal intubation. Its successful use with three patient groups is described: those with soft-tissue contractures of the mouth or neck; those with severe fractures of facial bones and/or mandible; those with unstable fractures or fracture-dislocations of the cervical spine. Fiberoptic bronchoscopy is felt to be the technique of choice when intubation is difficult, especially when there are contractures or deformities of the larynx, manidible, or cervical spine.

Adult↗
PubMed1973

Influence of Translocation of Photosynthetic Efficiency of Phaseolus vulgaris L.

Measurements of net photosynthesis show that in Phaseolus vulgaris L. the cultivar Michelite-62 exceeds the cultivar Red Kidney in net CO(2) uptake by 23 to 31%. Data on translocation of pulse label indicate that export of a pulse of photosynthetically assimilated (14)C from the source leaf of either M-62 or Red Kidney follows an exponential pattern and shows an initial rapid phase followed by a second slower phase. The steeper slope for both phases in M-62 suggests its rate of translocation of pulse label is higher than that of Red Kidney. Furthermore, only 38% of the (14)C remains in the leaf of M-62 after 8 hours, while Red Kidney retains up to 60% of the label. Leaf autoradiographs obtained after pulse labeling demonstrate a much faster rate of vein loading in M-62 and are considered evidence for the higher translocation efficiency of M-62. These results provide evidence for a positive correlation between photosynthetic efficiency and translocation efficiency in M-62 and Red Kidney and give support to our hypothesis that translocation is one of the important physiological factors controlling the varietal differences in photosynthetic efficiency in Phaseolus vulgaris.

Journal Article↗
PubMed1972

Intraspecific measurements of photorespiration.

The relative magnitudes of (a) CO(2) compensation concentration, (b) zero CO(2) intercept of the CO(2) response curve, (c) O(2) suppression of net photosynthesis, (d) differential (12)CO(2) and (14)CO(2) uptake, and (e) (14)CO(2) efflux into CO(2)-free air were determined in the dry bean (Phaseolus vulgaris L.) varieties Michelite-62 (M-62) and Red Kidney (RK). In comparing the two varieties for each of the above processes, there were three categories of response, M-62 > RK, M-62 = RK, and M-62 < RK. Since these processes did not give the same relative difference for the two varieties being studied, it was concluded that these phenomena cannot validly be used to estimate the magnitude of photorespiration, although they do identify its presence. The results suggest that photorespiration is but one component of O(2) inhibition of net photosynthesis and that photorespiration itself has two or more component metabolic pathways.

Journal Article↗
PubMedDate not supplied

Fetal effects of prophylactic ephedrine and maternal hypotension during regional anesthesia for cesarean section.

The purpose of this study was to evaluate the effects of a prophylactic intravenous bolus of ephedrine on the incidence and severity of maternal hypotension and on neonatal outcome. Term healthy parturients (n = 122) scheduled for elective repeat cesarean section under regional anesthesia were studied. Ninety-two women received 10 mg ephedrine as a prophylactic intravenous bolus prior to intrathecal epidural local anesthesia. Thirty parturients who served as controls did not receive prophylactic ephedrine. Maternal blood pressures, Apgar scores, and umbilical cord blood acid-base status were evaluated. Sixty-three of 92 women (69%) who received intravenous prophylactic ephedrine prior to regional anesthesia developed hypotension compared to 21 (70%) controls. The mean (+/- SD) lowest systolic blood pressure was similar in both groups (95.6 +/- 12.9 vs. 96 +/- 8.9 mmHg; P = 0.86). The mean (+/-SD) fetal pH was significantly lower with prophylactic ephedrine than controls (7.24 +/- 0.07 vs. 7.28 +/- 0.05; P = 0.001). The frequency of umbilical artery blood pH < 7.20 was 10.6% for the ephedrine group vs. 3.2% for controls (P = 0.024). Among newborns of hypotensive mothers, the frequency of umbilical artery blood pH < 7.20 was 30.2% and 4.6% for the ephedrine and control groups, respectively (P = 0.018). Intravenous prophylaxis with ephedrine did not significantly decrease the frequency of hypotension in women receiving regional anesthesia and resulted in a greater proportion of umbilical artery blood pH values < 7.20.

Anesthesia, Epidural↗
PubMedDate not supplied

Indirect sonographic guidance for epidural anesthesia in obese pregnant patients.

BACKGROUND AND OBJECTIVES: Obesity and edema frequently obscure anatomic landmarks and result in technical difficulties during epidural anesthesia administration. However, the method of indirect sonographic guidance permits identification of the midline by sagittal scan of the laminae of lumbar vertebrae 2, 3, and 4. METHODS: Thirty-six obese women scheduled for elective repeat cesarean delivery were prospectively studied. Use of a 5-MHz transducer positioned with the transducer center site over the second or third interspace allowed measurement of skin-to-lamina distance by the electronic calipers of a Toshiba SAL-32B or RT 3000 GE machine, prediction of needle depth for epidural puncture (EP), and skin marking of the site. After the transducer was removed, a 9.5- or 11.4-cm Tuohy needle was percutaneously advanced perpendicularly from the site until EP was achieved. RESULTS: Needle depth was measured by marker and measure, and epidural anesthesia was successfully administered to all patients. Simple linear regression analysis was performed with strong positive results. Indirect and continuous sonographic guidance studies designed to determine whether sonography reduces complications are planned.

Adult↗
PubMedDate not supplied

Reducing crying and irritability in neonates using a continuously controlled early environment.

A mother's "holding" environment has been shown to be effective in reducing infant crying and irritability. When mothers hold or cuddle their infants they create a microenvironment with stimuli similar to those of the intrauterine environment. Several of these same stimuli were incorporated into a cradle designed to provide a similar "holding" environment for the infant when the mother was not there. Ninety healthy term newborn infants were randomized to an experimental (n = 45) or control group (n = 45). The experimental group used a cradle that produced motion, sound, tactile (containment), and reduced-light stimuli at stimulus levels that initially approximated intrauterine sensory stimulation levels and gradually decreased to the levels of the home environment over 16 weeks. The control group used an identical cradle with no stimulus modulation features. Infants were placed in their respective cradles from 2 hours after birth during the times they would normally be placed in an infant bed. The mother-infant interaction or parenting style was not changed or manipulated. Mothers' use of the cradles did not differ significantly. An electronic status monitor measured and recorded infant presence and crying in the cradles. The Brazelton Neonatal Behavioral Assessment Scale test was done at 1 to 2, 14, and 24 days of age by "blinded" examiners. Additionally, phone calls and home visits were conducted by a registered nurse.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

A modified newborn intensive care unit environment may shorten hospital stay.

Premature infants with birth weights from 1121 to 2000 gm were assigned randomly to two groups. Experimental group infants were placed on a microprocessor-controlled cradle that provided levels of motion and sound analogous to those of the third-trimester intrauterine environment. Periods of motion totaling 50% of the time were randomized on and off; motion speed was reduced 35% during a 12-hour night period. A uterine souffle sound was generated continuously but varied in pulse rate and volume with the motion and speed of the bed. Experimental group infants (n = 20) were placed on the cradle under a radiant warmer as soon as their condition was stable clinically. Control group infants (n = 18) were usually placed initially under a radiant warmer and transferred to an incubator when their condition was stable. Otherwise, both groups received standard newborn intensive care unit care. The mean length of hospital stay was significantly shorter for experimental group infants than for control group infants after controlling for gestational age and weight on entry to the study. Experimental group infants began nippling earlier and stopped requiring gavage feedings sooner. Experimental group infants had a decreased incidence of apnea. Blinded Brazelton Neonatal Behavioral Assessment Scale scores for the Orientation and Range of State cluster scales were significantly better for experimental group infants. A retrospective contrast group of preterm infants who met study criteria had an average length of stay similar to that of the control group infants. These data support the hypothesis that appropriate levels and kinds of stimulation may facilitate the maturation of preterm infants.

Birth Weight↗
PubMedDate not supplied

Supraventricular tachycardia in a parturient under spinal anesthesia.

BACKGROUND AND METHODS: A 30-year-old woman with a history of palpitations was admitted for a repeat cesarean delivery at 41 weeks' gestation. Spinal anesthesia was administered. RESULTS: Supraventricular tachycardia and hypotension developed in the patient and were treated with boluses of ephedrine and phenylephrine. CONCLUSION: Phenylephrine may be used successfully for the treatment of SVT that results in hypotension under spinal anesthesia, and it may have advantages over ephedrine.

Adult↗