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PubMed1988

Urbanization, the informal sector and migration: issues for research and cooperation.

Only recently have development studies begun to examine the complex set of relationships between urbanization, the growth of the informal sector, and internal migration in Latin America. This paper suggests that the economic crisis of the 1980s has resulted in significant changes in these phenomena and that 1 of the most important changes has been the growth of return international migration between Latin American countries. Also of importance are the continued migration flows to North America. The paper argues that the interconnectedness of these phenomena requires more multinational research efforts.

Americas↗
PubMed2000

Effect of verapamil on cholesteatoma migration in vitro.

OBJECTIVES: It was previously shown that cholesteatoma migration in vitro is influenced by the calcium concentration of the culture medium. This study was designed to determine whether the calcium channel blocker verapamil affects cholesteatoma migration in vitro. METHODS: Cholesteatoma cells harvested from patients with chronic ear disease were grown in culture and were exposed to culture medium containing verapamil. The migration rate of the verapamil-exposed cells was compared with control rates. RESULTS: Verapamil at 300 microgram/L caused marked reduction in the rate of migration compared with control values. The migration rate returned to normal within 48 hours after verapamil was removed from the culture medium. Higher verapamil concentrations (500 microgram/L) caused complete detachment of the epithelial cells from the substrate within 24 hours. CONCLUSION: Our findings suggest that cholesteatoma migration in vitro is calcium channel dependent and can be reduced with calcium channel blockers such as verapamil.

Calcium↗
PubMed1995

Vasoactive intestinal peptide and substance P receptor antagonists improve postoperative ileus.

Octreotide, a somatostatin analogue that inhibits the release of most gut peptides, hastens the resolution of experimental postoperative ileus, suggesting that gut peptides mediate this process. We studied the role of two gut peptides involved in the control of normal gut motility, vasoactive intestinal peptide (VIP), and substance P (SP), in the initiation and maintenance of postoperative small bowel ileus in rats by preoperative administration of VIP and SP receptor antagonists, (VIP-ra and SP-ra). Thirty male Sprague-Dawley rats (300-350 g) underwent laparotomy. One half underwent placement of a duodenal catheter for transit studies while the other half had serosal electrodes placed on the proximal jejunum for myoelectric recordings. Six days later, animals were separated into three treatment groups of five each. Control animals were pretreated with ip saline, while the others received either VIP-ra or SP-ra prior to standardized laparotomy. Following abdominal closure, [Na51]CrO4 was injected into the duodenum and the animals were sacrificed 25 min later. The small bowel was then excised and divided into 10 equal segments. Small bowel transit was calculated as the geometric center of [Na51]CrO4 distribution. The interval until the return of migrating myoelectric complexes (MMCs) was determined in animals with intestinal electrodes. VIP-ra-treated rats demonstrated a 67% improvement in the geometric center of radiolabel relative to controls and SP-ra-treated rats had a 23% improvement (3.67 +/- 0.06 VIP-ra vs 2.69 +/- 0.09 SP-ra vs 2.20 +/- 0.09 control, P < 0.01). MMCs returned 180 +/- 17 min in controls vs 99 +/- 14 min in VIP-ra-treated rats (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1999

Development of patent Ascaris suum infections in pigs following intravenous administration of larvae hatched in vitro.

The normal tissue migration of Ascaris suum in the pig host involves larval development in the liver accompanied by considerable pathological changes. The vast majority of larvae that reach the small intestine are later expelled by unknown mechanisms. We show that when migration through the liver is bypassed by inoculation of pigs with an intravenous dose of larvae hatched in vitro, the larvae not only complete migration and return to the small intestine, but they also seem to have a greater chance of survival to adulthood. This technique offers new possibilities for studies on specific lung involvement in protective immunity, provides valuable information for the understanding of self cure by larval expulsion, and adds to our understanding of the evolution of migration of Ascaris larvae in tissues.

Animals↗
PubMed1977

Parasites of domestic and wild animals in South Africa. III. Oestrus spp. and Gedoelstia hässleri in the blesbok.

Four blesbok culled in the Rietvlei Nature Reserve, Pretoria, District during May 1972 were found to harbour large burdens of 1st instar Oestrus spp. larvae and from 16-37 3rd instar larvae of Oestrus macdonaldi. They were also infested with large numbers of 1st instar Gedoelstia hässleri larvae but only 2 harboured 3rd stage larvae of this species. During an 18-month period 34 blesbok were culled in pairs in the Percy Fyfe Nature Reserve, Potgietersrus District. These antelope harboured peak numbers of 1st instar Oestrus spp. larvae during February, July and December but few if any during early October. Third instar Oestrus variolosus larvae were generally recovered from July-February and those of O. macdonaldi during July 1972 and from May-September 1973. Some 1st instar larvae of these flies appeared to undergo a pulmonary migration before returning to the naso-pharyngeal area to mature. The pupal period of O. variolosus varied from 67 days during the spring to 35 days during the summer. G. hässleri larvae reached peak numbers from October 1972-January 1973 and during May and June 1973. The lowest numbers were recovered from August-October 1973. Recovery and measurement of 1st instar larvae indicated that they either undergo an ocular-cranial or ocular-vascular-pulmonary migration before reaching the naso-pharyngeal area. Pupal periods varied from 46 days for flies hatching during October to 22 days for those hatching during December.

Animal Husbandry↗
PubMed2004

Spontaneous correction of pathologic tooth migration and reduced infrabony pockets following nonsurgical periodontal therapy: a case report.

This case report describes the spontaneous correction of pathologic tooth migration and reduced infrabony pockets after nonsurgical periodontal therapy. A 3-mm diastema between the maxillary incisors was closed completely, and the mandibular teeth, which had migrated pathologically, returned to the optimal position. Clinical evaluation showed a significant reduction in probing depth, with increased clinical attachment and bone deposition demonstrated radiologically.

Alveolar Bone Loss↗
PubMed1999

A new thermo-expandable shape-memory nickel-titanium alloy stent for the management of ureteric strictures.

OBJECTIVE: To assess the ease on insertion, patient tolerance, undesirable side-effects, degree of encrustation and duration of upper tract decompression with a new thermo-expandable shape memory alloy ureteric stent. PATIENTS AND METHODS: From November 1996 to October 1998, 15 patients with ureteric strictures were treated with a new nickel-titanium shape-memory alloy stent, the Memokath 051 (Engineers & Doctors A/S, Hornbaek, Denmark). A total of 22 insertions were carried out. Ureteric obstruction was caused by recurrent colorectal carcinoma in four patients; two patients each with transitional cell carcinoma of the bladder, iatrogenic injury or ischaemia at the uretero-ileal anastomosis; and one patient each with metastatic lymph nodes from prostatic carcinoma, radiation-induced fibrosis, pelvi-ureteric junction obstruction, metastatic carcinoma of the vagina and extra-luminal endometriosis. The stent has a shaft diameter of 9 F and its proximal end expands to 17 F. The first three patients were treated with the original version, which expanded to 14 F. The unexpanded stent is inserted into the ureter after initial dilatation of the stricture to 12 F. The stent is expanded by injection with sterile water preheated to 50 degrees C. The procedures were carried out under a general anaesthetic and patients were allowed home the next day. The follow-up protocol included initial intravenous urography (IVU) at 6 weeks, with assessment of a mid-stream urine sample and renal function tests. These were repeated at 3-monthly intervals. Isotopic renography was performed when indicated. RESULTS: The mean (range) follow-up was 10.6 (2-21) months; there was complete relief of upper tract obstruction in all patients. No stent-related symptoms, e.g. pain, sepsis, haematuria or frequency, were noted and no encrustation has occurred so far. The stent migrated in the first three patients with the original smaller diameter of stent but decompression of the upper tracts was maintained. None of the modified wider stents have migrated. The return of peristalsis in the proximal ureter was detected during IVU. There was no apparent endothelial growth through the stent material and no re-admissions for stent-related complications. CONCLUSION: Early experience with this new stent is very encouraging. All patients have maintained satisfactory decompression of their upper tracts with no need for repeated hospitalization for stent changes. There have been no untoward side-effects so far. This stent appears to have a valuable place in the long-term management of ureteric strictures; it is probably most suited for malignant ureteric obstruction. It should be considered in the management of selected benign strictures that require long-term JJ stenting.

Adult↗
PubMed2004

Disentangling ligand migration and heme pocket relaxation in cytochrome P450cam.

In this work we show that ligand migration and active site conformational relaxation can occur independently of each other in hemoproteins. The complicated kinetics of carbon monoxide rebinding with cytochrome P450cam display up to five distinct processes between 77 K and 300 K. They were disentangled by using a combination of three approaches: 1), the competition of the ligand with xenon for the occupation of internal protein cavities; 2), the modulation of the amount of distal steric hindrance within the heme pocket by varying the nature of the substrate; and 3), molecular mechanics calculations to support the proposed heme-substrate relaxation mechanism and to seek internal cavities. In cytochrome P450cam, active site conformational relaxation results from the displacement of the substrate toward the heme center upon photodissociation of the ligand. It is responsible for the long, puzzling bimodal nature of the rebinding kinetics observed down to 77 K. The relaxation rate is strongly substrate-dependent. Ligand migration is slower and is observed only above 135 K. Migration and return rates are independent of the substrate.

Binding Sites↗
PubMed1985

Characteristics of cellular and humoral immune responses after immunization with different rabies vaccines.

Three rabies vaccines were compared: 1. the Fermi type vaccine, a phenol-treated suspension of brain tissue from infected sheep; 2. a virus grown in sheep brain, purified from the contaminating material to 85-90% and inactivated with beta-propiolactone; 3. and the MNIIP-74 strain cultured in Japanese quail embryo cells and inactivated with beta-propiolactone. A single immunization of mice with any of the preparations resulted in about 50% inhibition of splenocyte migration after 2 days; by day 15 the inhibition was 95-98%. By day 45 the migration index returned to the initial level. Increased ability to blast transformation in splenocytes was found by day 15, reached the maximum (160 to 212% of the control level taken for 100%) by day 30, and then began to decrease. The most marked change in blast transformation was brought about by the purified cerebral vaccine, while the less marked one by the tissue culture vaccine. The titre of virus-neutralizing antibodies reached a maximum after 15-30 days, 60 days after immunization it dropped twice. The resistance of mice to intracerebral infection with the rabies virus shortly after immunization might be due to cellular protective factors, while at later intervals it correlated with the level of virus-neutralizing antibodies.

Animals↗
PubMed1979

The development of immunity to Parascaris equorum infection in the foal.

Following infection with 8000 Parascaris equorum eggs in two- to four-week-old foals reared under worm-free conditions a high percentage of the infective dose completed its tissue migration and returned to the small intestine. Patent infections were establisehd between 81 and 104 days after infection and high faecal egg counts were recorded. A group of six- to 12-month-old foals, which had been either reared under worm-free conditions or exposed to natural ascarid and strongyle infections on pasture, received a similar infection of 8000 P equorum eggs. Compared with the younger foals there was a marked reduction in the number of larvae reaching the small intestine. Also, patent infections were established less frequently (50 per cent of cases) and, when present, the faecal egg counts remained low.

Animals↗
PubMed1997

Occupational change, employer change, internal migration, and earnings.

"In this paper I use microdata from the [U.S.] Panel Study of Income Dynamics to measure the financial returns to intercounty and interstate migration for individuals in a temporal framework accounting for gains that accrue over time.... To account for the indirect effects of migration on earnings, explanatory variables are created by interacting migration status with: (1) occupational change, (2) employer change and (3) changes in both occupation and employer. These interaction terms are then included in the earnings functions. Earnings are estimated for three years subsequent to the migration decision to account for the financial returns to migration accruing over time. Results indicate that, when estimating earnings, the use of a simple migration dummy variable will mask the indirect effects of migration on earnings."

Americas↗
PubMed1986

Migration in vitro by blood and exudate neutrophils assessed serially during an inflammatory response.

Migration in vitro by blood and inflammatory neutrophils has been compared serially during an inflammatory response. Using an experimental pig model, neutrophils are isolated from the peripheral blood and from the pleural space at hourly intervals after an intrapleural challenge with zymosan activated pig serum (ZAS). Following acepromazine sedation and halothane anesthesia, blood neutrophil migration was transiently reduced. By 1 hour random and directed migration of blood neutrophils returned to normal. Directed and random migration of exudate neutrophils was markedly decreased to both a stimulus-specific (ZAS) and an unrelated (LTB4) chemoattractant. After 3 hours, migration by exudate neutrophils was similar to migration by blood neutrophils examined in parallel. These findings emphasize the importance of performing serial evaluations of cell function during an inflammatory response.

Animals↗
PubMed1993

Ketorolac prevents postoperative small intestinal ileus in rats.

The effect of ketorolac, a parenterally administered, nonsteroidal anti-inflammatory drug, was examined in a rat model of postoperative ileus. Small intestinal transit was measured by calculating the geometric center (GC) of distribution of 51CrO4. Laparotomy significantly delayed transit (GC: 2.2 +/- 0.2 after laparotomy versus 5.6 +/- 0.5 for unoperated controls, p < 0.01). The administration of ketorolac (1 mg/kg) improved the GC to 5.2 +/- 0.2 (p < 0.01), indicating normal intestinal transit after surgery in ketorolac-treated animals. Small intestinal myoelectric activity was recorded in rats with implanted electrodes. Animals treated with saline 2 hours postoperatively did not show return of the migrating myoelectric complex (MMC) in 183 +/- 25 minutes. In contrast, rats receiving ketorolac postoperatively had return of MMC activity in 59 +/- 18 minutes (p < 0.01). Preoperative ketorolac treatment reduced the duration of MMC inhibition after surgery from 197 +/- 55 minutes to 13 +/- 5 minutes (p < 0.05) when compared with saline. In summary, ketorolac hastens the return of MMC activity when given postoperatively. When ketorolac is administered preoperatively, it completely prevents the delay in intestinal transit and the inhibition of myoelectric activity seen in postoperative ileus. We concluded that ketorolac may be of benefit in the prevention and treatment of postoperative ileus.

Animals↗
PubMed1999

Temporary migration and regional development in China.

"A new approach to migration in developing countries is used in this paper, which integrates into the migration process the experiences of moving to cities, working in urban areas, and returning to the countryside. As a result, rural labor migration is directly linked to rural development through remittances, as well as through physical and human capital brought back by return migrants. Migration information is mainly drawn from China's 1995 1% National Population Survey.... It has been found that patterns of temporary migration are mainly shaped by the magnetic force of the growth-pole region. Job opportunities created there in labor-intensive industries have attracted large numbers of migrants, first from the surrounding rural areas and then from the peripheral regions, enhancing migration propensity in both areas."

Asia↗
PubMed1993

Asymmetric information and the brain drain.

"Within an asymmetric information framework, we investigate the effects of subsidies for return [to developing countries] when the size of the foreign student population is endogenous. Given the stability condition and the assumption that the education system is effective in the home country, we show that subsidies for return always act to improve the average ability of returning Ph.D.s but the impact upon the number of emigrants is ambiguous."

Demography↗