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Biomedical subjects

C Becker

Publications and source records attributed to C Becker.

At least 37 records · Page 2Linked to original sources
PubMed1989

The effects of a progestin-only oral contraceptive (levonorgestrel 0.03 mg) on breast-feeding.

This study was a non-randomized clinical trial which compared the breast-feeding experience of 250 Argentine women taking levonorgestrel 0.03 mg daily (begun one week after delivery) with that of 250 women using non-hormonal contraceptives. Weight gain of unsupplemented infants, the most important of the several criteria used to assess breast-feeding performance, was similar for the two contraceptive groups. Levonorgestrel users began supplementary feeding of their infants significantly later than did non-hormonal users; levonorgestrel users were also somewhat less likely to discontinue breast-feeding during the study period. The two contraceptive groups were similar with regard to several other measures of breast-feeding performance: growth of all infants (regardless of supplementation), patterns of contraceptive discontinuation, mothers' subjective impressions of breast-milk sufficiency, and comparison of supplementation initiation with previous experience.

Adult↗
PubMed1989

Changes in survival following stroke in five North Carolina counties observed during two different periods.

We evaluated survival following stroke for patients from a five-county area of rural North Carolina enrolled in either of two community hospital-based stroke survey programs. In this area, the first program enrolled 843 stroke patients between 1970 and 1973 and the second program enrolled 786 stroke patients between 1979 and 1980. One-year survival increased from 49% in the first program to 62% in the second for all stroke patients, from 54% to 68% for patients with cerebral infarction, and from 18% to 55% for patients with cerebral hemorrhage. While other reports have attributed declining stroke mortality to a decline in the incidence of stroke, our study suggests that increased survival after stroke may account for a large portion of the decrease in stroke mortality.

Actuarial Analysis↗
PubMed1989

Increased muscle regeneration after repair of divided motor nerve with neuronotrophic factors containing glue.

Neuronotrophic factors (NTFs) directed to spinal cord motor neurons were collected in rats within silicone nerve regeneration chambers according to LONGO et al. (1983b). Unilateral addition of NTFs to the fibrin glue used for the repair of divided sciatic nerves improved locally nerve regeneration without affecting the controlateral side. Nerve regeneration was assessed by weight gain of the reinnervated muscles and by radioactive labelling of the acid-soluble phosphate fractions of both nerve Schwann cells and reinnervated muscle cells. Fast gastrocnemius and slow soleus muscles, the motor nerve of which had been repaired with added NTFs, were significantly heavier (21 and 28%) than their controlateral controls, and the metabolic dedifferentiation attendant on post-division nerve repair was less marked. It is suggested that this experimental nerve regeneration model is suitable to test potential nerve-active agents in vivo, under conditions close to the usual clinical setting, with, as ultimate goal, the improvement of the end-results of microsurgical repair of peripheral nerve in man.

Animals↗
PubMed1989

Using chromatography in downstream processing.

This article concludes the series on the use of chromatography for downstream processing. Although it has only scratched the surface when considering the number of parameters involved in process chromatography, it does give a broad overview including the choice of components through process standards. Pharmacia LKB Biotechnology has had more than 15 years experience in the design development and running of large scale chromatographic processes. During this time the company has gathered a vast amount of experience and information on the key points to successful product purification. Pharmacia LKB can advise on the choice of techniques and the development of a separation process up to full production scale.

Automation↗
PubMed1988

A blind trial of silicone chamber fluid in nerve regeneration in the rat.

The nerve growth-promoting effects of the fluid accumulating in vivo from 1 to 28 days within silicone chambers were tested on the sciatic nerves of rats. We measured the elongation of sensory axons following nerve transection repaired by means of fibrin sealant allowing local application of the fluid. We found no difference between transections treated with chamber fluid and controls.

Animals↗
PubMed1988

[The cubital flap].

The authors describe a flap with a pedicle derived from the dorsal branch of the ulnar artery. The ulnar artery gives rise to the dorsal ulnar artery 2 to 5 cm before the pisiform. This artery passes under the flexor carpi ulnaris muscle, accompanied by the dorsal branch of the ulnar nerve. It supplies an area 10 to 20 cm long by 5 to 9 cm wide on the ulnar side of the forearm and it also supplies the skin lying over the last three metacarpals on the dorsum of the hand and the Vth abductor. This artery also sends a branch to flexor carpi ulnaris and to the pisiform. It is now possible to trace a large flap in the forearm without interrupting the arterial axis. Large defects of the dorsum of the hand, wrist, thenar and hypothenar eminences can be covered by this pedicle or island flap. This artery is remarkably constant. Five clinical cases are presented.

Adult↗
PubMed1988

Potential-dependent allosteric modulation of 1,4-dihydropyridine binding by d-(cis)-diltiazem and (+/-)-verapamil in living cardiac cells.

We have studied allosteric effects of the Ca channel blockers d-(cis)-diltiazem, (+/-)-verapamil, and (S)- and (R)-devapamil on the specific binding of the 1,4-dihydropyridine derivative (+)-[3H]PN 200-110 to intact tissue cultured rat heart cells. In polarized cells (membrane potential, -38 +/- 4 mV) d-(cis)-diltiazem (5 microM) increased the affinity of the radiolabel 2-4-fold causing 100-187% enhancement of binding at (+)-PN 200-110 concentrations below 0.5 nM. (+/-)-Verapamil (0.1-3 microM) had a similar, although smaller, effect on (+)-PN 200-110 binding. The two enantiomers of devapamil were without effect. In depolarized cells (membrane potential, 0 mV) d-(cis)-diltiazem had a small and the phenylalkylamines a strong inhibitory effect on (+)-PN 200-110 binding, mainly due to a reduction of binding affinity. At 50% receptor occupation by the radioligand, (R)-devapamil, (+/-)-verapamil, and (S)-devapamil displaced 40, 55, and 75%, respectively, of specifically bound radiolabel. Half-maximal effects were reached with 50, 20, and 4.5 nM, respectively, of the three compounds. Compared with nominally Ca-free medium (containing 3-5 microM Ca), addition of 1.25 mM CaCl2 caused an increase in the maximal binding capacity for (+)-PN 200-110 in both polarized and depolarized cells. However, Ca had only marginal effects on the allosteric interactions between (+)-PN 200-110, d-(cis)-diltiazem, and verapamil. We conclude from our results that positive cooperative interactions between Ca channel blockers prevail under conditions in which the voltage-dependent Ca channel can fluctuate between closed, open, and inactivated states. Negative cooperativity is usually observed under conditions in which all channels are inactivated (depolarized cells, fragmented membranes). Therefore, it is impossible to predict the type and the extent of allosteric interactions in vivo from studies in cell homogenates.

Allosteric Regulation↗
PubMed1988

[The ulnar flap].

A new skin or fascial flap is described, based on the dorsal ulnar artery. In hundred fresh cadaveric forearms this vessel was constant with a diameter of 1 to 1.3 mm, passing dorsally from the ulnar artery deep to the flexor carpi ulnaris muscle. It supplies the skin and the fascia in the distal two thirds of the ulnar side of the forearm (length from 9 to 20 cm; width 1.5 to 10 cm). A flap based on this vessel can cover defects of the dorsal and palmar aspects of the hand and wrist, the thenar and the hypothenar eminence. It can be used as a fascial flap to avoid fibrosis around the median nerve and the tendons. The authors show the anatomy and some clinical cases.

Adult↗
PubMed1988

[Transfer of free lymphatic flaps . Microsurgery and anatomical study].

Results of an experimental study in the rat showed that a healthy gland transplanted into a lymphedematous zone can function for a sustained period and improve the edema. It is possible, therefore, without adversely affecting the lower limb lymphatic circulation, to transplant the superior external group of inguinal glands into the axilla of a "big arm".

Animals↗
PubMed1987

Mutagenicity experiments on agroclavines, new natural antineoplastic compounds.

Agroclavine, an alkaloid produced by some species of fungi and dicotyledon plants, and its 1-alkylated derivatives are potentially useful as antineoplastic drugs, since they exert potent and selective cytostatic effects. In the present study, we have investigated agroclavine and its 1-propyl and 1-pentyl derivatives for mutagenicity. The genetic end point studied was the reversion of strains of Salmonella typhimurium (TA 100, TA 98, TA 1537) and Escherichia coli (WP2 uvrA), auxotrophic for histidine and tryptophan, respectively. The compounds were tested directly and in the presence of a mammalian xenobiotic-metabolizing system. In the direct test, agroclavine and the two alkylated derivatives examined exhibited substantial bacteriotoxicity but no mutagenicity. Addition of NADPH-fortified postmitochondrial supernatant fraction of rat liver homogenate led to a clear-cut decrease in bacteriotoxicity and to the formation of mutagenic products. Each compound was effective in all three strains of S. typhimurium used. In E. coli only spurious effects were seen. 1-Pentylagroclavine, the most hydrophobic compound in the series, was the strongest mutagen. Agroclavine, the least hydrophobic compound, was the weakest. The mutagenic potencies and efficacies of all these test compounds were much weaker than those of the positive controls, which were known mutagens and carcinogens. Moreover, the differential effect of metabolism by liver enzymes demonstrates that the toxicity and mutagenicity of agroclavine and its derivatives are caused by different chemical species. Hence, it may be possible to develop derivatives that are cytotoxic but not mutagenic.

Animals↗
PubMed1987

Differential effects of various secretagogues on quantal transmitter release from mouse motor nerve terminals treated with botulinum A and tetanus toxin.

Electrophysiological and electron microscopic techniques were used to investigate the actions of potassium depolarization, black widow venom (BWSV), Ca2+-ionophore A 23187 and hyperosmotic solution on mouse hemidiaphragms poisoned in vitro with botulinum A toxin (BoTx) and tetanus toxin (TeTx). These neurotoxins reduced the frequency of miniature endplate potentials (m.e.p.ps) from 5/s of the control to 2/min and 21/min, respectively. High potassium (25 mmol/l) increased the m.e.p.p.-frequency at BoTx- and TeTx-poisoned endplates to 30/min and 50/s, respectively. The ultrastructure of endplates showed no obvious changes. BWSV (0.04 glands/ml) was just as effective in promoting transmitter release from BoTx-treated endplates as in control preparations. Electron micrographs revealed depletion of vesicles as well as swollen and disrupted mitochondria. When preparations were pretreated with TeTx, BWSV only moderately increased transmitter release and no alterations of the ultrastructure could be observed. At TeTx- or BoTx-poisoned endplates Ca2+-ionophore A 23187 usually produced an extreme reduction of m.e.p.p.-frequency (0.005/s), sometimes preceded by a short burst-like release. The ultrastructure of these endplates was not obviously affected. Application of hyperosmotic solution to BoTx- or TeTx-poisoned preparations further reduced the already low m.e.p.p.-frequency. These results further demonstrate that TeTx and BoTx act at different sites in the transmitter releasing process.

Animals↗
PubMed1987

Pericardial effusion causes interstitial pulmonary edema in dogs.

The pulmonary effects of pericardial effusion were studied in eight anesthetized dogs, with emphasis on lung mechanics, O2 exchange, and extravascular thermal lung volume (ETV) accumulation, while warm saline was instilled into the pericardium to elevate pericardial pressure. The results were compared with those from four time-controlled and sham-operated dogs. ETV, as measured by a double-indicator technique, increased from 8.1 +/- 0.8 ml/kg at a pericardial pressure of 0 mm Hg to 12.9 +/- 2.1 ml/kg at 11.0 mm Hg (p less than .01). In the control group, ETV increased from 6.5 +/- 0.7 to 8.2 +/- 0.5 ml/kg over an equal time span. This increase in ETV in the experimental dogs was inversely related to pulmonary compliance, which decreased by 29% as ETV increased (p less than .05), whereas in the time-controlled group of animals it decreased by 8.8%. Arterial PO2 did not deteriorate during the protocol in either group. Histologic examination showed increased interstitial fluid, but neither alveolar fluid nor septal edema, and gravimetric measurements of lung liquid were also consistent with interstitial fluid accumulation in experimental but not control animals. These findings are concordant with the clinical observation that alveolar edema is rarely seen in the presence of pericardial tamponade. Conceivably, progression from interstitial to alveolar edema did not occur both because of the low pulmonary blood flow that occurs as part of pericardial tamponade physiology and/or because the hydrostatic pressures were not elevated enough to produce higher rates of fluid transudation.

Animals↗
PubMed1987

Voltage-dependent cooperative interactions of calcium channel ligands in intact cardiac cells.

Voltage-dependent Ca channels were studied in living, tissue cultured rat heart cells using patch clamp analysis of single channels and radioligand binding studies at different membrane potentials. Ca channel activating and blocking dihydropyridines (DHP) show cooperative interaction and, therefore, bind to at least two different binding sites on the channel protein. Cooperative interactions between activating and blocking DHP, between DHP and verapamil and between DHP and diltiazem are all voltage dependent. The type of interaction in polarized cells and hence, the possible effects in vivo cannot be predicted from studies in cell homogenates.

Allosteric Site↗
PubMed1986

Acute effects of routine firefighting on lung function.

We undertook a study to determine the acute effects of routine firefighting on lung function and the relationship between these acute effects and nonspecific airway responsiveness. For 29 firefighters from a single fire station, we calculated the concentration of methacholine aerosol that caused a 100% increase in specific airway resistance (Pc100). Over an 8-week period we than measured FEV1 and FVC in each firefighter before and after each 24-hr workshift and after every fire. From 199 individual workshifts without fires, we calculated the mean +/- 2 SD across-workshift change in FEV1 and FVC for each firefighter. Eighteen of 76 measurements obtained within 2 hr after a fire (24%) showed a greater than 2 SD fall in FEV1 and/or FVC compared to two of 199 obtained after routine workshifts without fires (1%; p less than .001). On 13 of 18 occasions when spirometry decreased significantly, we obtained repeat spirometry (postshift) 3-18.5 hr after fires, and on four of these occasions FEV1 and/or FVC were still more than 2 SD below baseline. Decrements in spirometry occurred as often in firefighters with high Pc100s as in those with low Pc100s. In two firefighters in whom FEV1 and FVC fell by more than 10% after fires, we repeated measurements of methacholine sensitivity, and it was increased over the prestudy baseline. These findings suggest that routine firefighting is associated with a high incidence of acute decrements in lung function.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗