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At least 811 records · Page 45Linked to original sources
PubMed1997

Heart rates of northern elephant seals diving at sea and resting on the beach.

Heart rates of northern elephant seals diving at sea and during apnoea on land were monitored to test whether a cardiac response to submergence is an important factor in their ability to make repetitive, long-duration dives. Seven juvenile northern elephant seals were captured at Año Nuevo, CA, instrumented and translocated to release sites around Monterey Bay. Heart rate and dive depth were recorded using custom-designed data loggers and analogue tape monitors during the seals' return to Año Nuevo. Heart rates during apnoea and eupnoea were recorded from four of the seals after they hauled out on the beach. Diving patterns were very similar to those of naturally migrating juveniles. The heart rate response to apnoea at sea and on land was a prompt bradycardia, but only at sea was there an anticipatory tachycardia before breathing commenced. Heart rate at sea declined by 64% from the surface rate of 107 +/- 3 beats min-1 (mean +/- S.D.), while heart rate on land declined by 31% from the eupnoeic rate of 65 +/- 8 beats min-1. Diving heart rate was inversely related to dive duration in a non-linear fashion best described by a continuous, curvilinear model, while heart rate during apnoea on land was independent of the duration of apnoea. Occasionally, instantaneous heart rate fell as low as 3 beats min-1 during diving. Although bradycardia occurs in response to apnoea both at sea and on land, only at sea is heart rate apparently regulated to minimise eupnoeic time and to ration oxygen stores to ensure adequate supplies for the heart and brain not only as the dive progresses normally but also when a dive is abnormally extended.

Animals↗
PubMedDate not supplied

Effect of cotton, hemp, and flax dust extracts on lung permeability in the guinea pig.

Byssinosis is an occupational lung disease in textile mill workers exposed to the respirable dusts of cotton, hemp, and flax. This study investigated the influence of aqueous extracts from these dusts on overall lung permeability in the guinea pig as an index of respiratory epithelial damage. Lung permeability was assessed by absorption into blood from the lung of inhaled technetium-99m diethylenetriamine penta-acetate (Tc-DTPA) using gamma-scintigraphy. The half-life for Tc-DTPA absorption (t1/2) was significantly reduced following a 4-week inhalation treatment with cotton, hemp, or flax dust extracts when compared to saline control. There was at least a partial return to normal permeability 7 days after stopping treatment. A single inhalation of extract did not affect the t1/2, but increased the number of neutrophils in bronchoalveolar lavage fluid 24 h postexposure. Neutrophil migration into the airspaces therefore appeared to precede the increased lung permeability. Long-term exposure was not associated with respiratory epithelial shedding, suggesting that the increased permeability reflects a loss of epithelial tight junction integrity arising from repeated exposure to as yet undefined agents in these dusts.

Absorption↗
PubMed1975

The equivalence of United States census data for persons of Russian stock or descent with American Jews: an evaluation.

While the U.S. Bureau of the Census has had a long-standing policy of abstaining from enumerating the religious beliefs or backgrounds of the American people, at least two-thirds of the Jewish population of the United States has been enumerated in decennial censuses and sample surveys in the guise of persons of Russian stock or origin. This has come about through the migration policy of the old Russian Empire and the statistical categories utilized by American immigration authorities and by the U. S. Bureau of the Census for immigrants and their children. Comparisons between the returns from an ethnic survey and a survey on the religious composition demonstrate the close congruence between persons of Russian stock or descent and American Jews on the national level.

Adolescent↗
PubMed1998

The mesh plug technique for recurrent groin herniorrhaphy: a nine-year experience of 407 repairs.

BACKGROUND: Recurrent inguinal hernias can be repaired efficaciously by mesh plug techniques, which have had better results than traditional tissue-based repairs in several small studies. This report provides a detailed description and assessment of the anterior, tension-free, "umbrella" mesh plug method for recurrent groin herniorrhaphy. METHODS: We performed a retrospective analysis of 407 patients with recurrent inguinal and femoral hernias treated with an umbrella mesh plug repair since 1989. Information was recorded about postoperative recovery and complications, and patients were examined for rerecurrences 1 week after operation and annually thereafter. RESULTS: Of the 320 patients with a first-time recurrence, 6 (2%) had a recurrence after placement of a mesh plug. Of the 87 patients who had undergone 2 or more prior repairs, 8 (9%) had a rerecurrence subsequent to a mesh plug hernioplasty. Nine (64%) of the 14 rerecurrences were noted within 1 year of operation; 4 (29%) were found 2 years after operation and 1 (7%) during postoperative year 3. During the 9 years of follow-up study, a mesh plug has not been involved in any infectious process requiring removal. There have been no instances of draining sinus tracts, ischemic orchitis, long-term pain, vascular and embolic phenomena, or plug erosion and migration. Two hundred fifteen (53%) of the patients took no pain medication. One hundred fifty-nine patients (39%) used nothing more than nonprescription pain medicine. Three hundred seventy-five patients (92%) returned to normal daily activities within 4 days of the herniorrhaphy. CONCLUSIONS: Patients with recurrent groin hernias, who undergo a minimal-dissection umbrella mesh plug repair, have a rapid recovery and few postoperative complications.

Follow-Up Studies↗
PubMed2004

Effects of peritoneal injury and endotoxin on myoelectric activity and transit.

BACKGROUND: The combined effects of peritoneal injury and intraabdominal infection on gastrointestinal motility in postoperative ileus are poorly understood MATERIALS AND METHODS: Sprague Dawley rats underwent placement of three electrodes on the small intestine and a tube gastrostomy. Animals were divided into four groups: a control (n = 12), a peritoneal injury (PI, n = 12), a peritoneal injection of lipopolysaccharide (LPS, n = 12), and a LPS + PI group (n = 12). After myoelectric activity recording on postoperative day (POD) 1, half of the rats in each group underwent intestinal transit studies. The remainder of the rats underwent another myoelectric activity recording as well as intestinal transit study at 48 h after operation RESULTS: Although six to eight of rats in the control, PI, and LPS groups recovered migrating myoelectric complex (MMC) on POD 1, no rats in the LPS + PI group recovered MMC by POD 1. The transit distance on POD 1 in the PI (36 +/- 2.5 cm) and LPS + PI group (38 +/- 2.8 cm) was shorter than that in the control group (53 +/- 2.0 cm, P < 0.05) CONCLUSIONS: Full recovery of liquid intestinal transit precedes the return of MMC activity after abdominal surgery in the rats. Peritoneal injury causes decreased intestinal transit and when combined with intraabdominal injection of LPS may cause the delayed recovery of MMC activity.

Abdomen↗
PubMed1986

[Migratory circuits in western Mexico].

The author examines patterns of internal and international migration in western Mexico. "Drawing on data from different sources and statistics, the essay demonstrates the importance of both types of migration, the changes in endogenous and exogenous factors which have affected the life and the migratory patterns of the population of this region. The migratory circuit being a flow not only of persons, but of goods and capital as well, the cities, specifically that of Guadalajara, have a strategic importance. They fulfill various functions and have become the backbone of the migratory process: they serve as centers for attracting and 'hosting' internal migrants as well as places of origin for other migrants; jumping-off points for international migrants; and the milieu in which many returning migrants of rural origin settle." (SUMMARY IN ENG AND FRE)

Americas↗
PubMed1995

Up-regulation of integrin alpha 5 beta 1 expression by interleukin-6 in rabbit corneal epithelial cells.

Interleukin-6 (IL-6) has been shown to promote the attachment of rabbit corneal epithelial cells to fibronectin-coated substratum and ex vivo migration of the cells on the corneal stroma. To examine whether IL-6 promotes cell attachment through up-regulation of expression of integrin alpha 5 beta 1, i.e., the major cell surface fibronectin receptor, we quantified the levels of both alpha 5 and beta 1 subunit transcripts by reverse transcription-polymerase chain reaction in cultured rabbit corneal epithelial cells pretreated with various concentrations of IL-6. The levels of both alpha 5 and beta 1 mRNAs were dose-dependently elevated by IL-6, attaining 1.5- and 1.8-fold increases, respectively, at 10 ng/ml. The stimulatory effect of IL-6 was transient; the levels of both subunit mRNAs reached a maximum 1 h after the addition of IL-6 and returned to the basal levels after 6 h. The IL-6-induced up-regulation of integrin alpha 5 and beta 1 mRNAs was also confirmed by Northern blot analysis. These results indicate that the increased attachment of corneal epithelial cells to fibronectin and enhanced ex vivo migration on corneal stroma by IL-6 is, at least in part, due to the temporal up-regulation of integrin alpha 5 beta 1 expression in corneal epithelial cells.

Amino Acid Sequence↗
PubMed2003

Overexpression of glutamic acid decarboxylase-67 (GAD-67) in gonadotropin-releasing hormone neurons disrupts migratory fate and female reproductive function in mice.

gamma-Aminobutyric acid (GABA) inhibits the embryonic migration of GnRH neurons and regulates hypothalamic GnRH release. A subset of GnRH neurons expresses GABA along their migratory route in the nasal compartment before entering the brain, suggesting that GABA produced by GnRH neurons may help regulate the migratory process. To examine this hypothesis and the possibility that persistence of GABA production by GnRH neurons may affect subsequent reproductive function, we generated transgenic mice in which the expression of glutamic acid decarboxylase-67 (GAD-67), a key enzyme in GABA synthesis, is targeted to GnRH neurons under the control of the GnRH gene promoter. On embryonic d 15, when GnRH neurons are still migrating, the transgenic animals had more GnRH neurons in aberrant locations in the cerebral cortex and fewer neurons reaching the hypothalamic-preoptic region, whereas migration into the brain was not affected. Hypothalamic GnRH content in mutant mice was low during the first week of postnatal life, increasing to normal values during infantile development (second week after birth) in the presence of increased pulsatile GnRH release. Consistent with these changes, serum LH and FSH levels were also elevated. Gonadotropin release returned to normal values by the time steroid negative feedback became established (fourth week of life). Ovariectomy at this time demonstrated an enhanced gonadotropin response in transgenic animals. Although the onset of puberty, as assessed by the age at vaginal opening and first ovulation, was not affected in the mutant mice, estrous cyclicity and adult reproductive capacity were disrupted. Mutant mice had reduced litter sizes, increased time intervals between deliveries of litters, and a shorter reproductive life span. Thus, GABA produced within GnRH neurons does not delay GnRH neuronal migration, but instead serves as a developmental cue that increases the positional diversity of these neurons within the basal forebrain. In addition, the results suggest that the timely termination of GABA production within the GnRH neuronal network is a prerequisite for normal reproductive function. The possibility arises that similar abnormalities in GABA homeostasis may contribute to syndromes of hypothalamic amenorrhea/oligomenorrhea in humans.

Animals↗
PubMed2006

Unique ability of activated CD4+ T cells but not rested effectors to migrate to non-lymphoid sites in the absence of inflammation.

Recent studies suggest that effector T cells generated by immune responses migrate to multiple non-lymphoid sites, even those without apparent expression of antigen or inflammation. To investigate the ability of distinct CD4(+) T lymphocyte subsets to enter and persist in non-lymphoid, noninflamed compartments, we examined the migration and persistence of naïve, effector, and rested effector CD4(+) T cells generated in vitro following transfer to nonimmunized adoptive hosts. Th1 and Th2 effectors migrated to both lymphoid and non-lymphoid organs (peritoneum, fat pads, and lung). In contrast, rested effectors and naïve cells migrated only to lymphoid areas. Adhesion molecule expression, but not chemokine receptor expression, correlated with the ability to enter non-lymphoid sites. Donor cells persisted longer in lymphoid than in non-lymphoid sites. When hosts with naïve and memory donor cells were challenged with antigen, effectors developed in situ, which also migrated to non-lymphoid sites. Memory cells showed an accelerated shift to non-lymphoid migration, in keeping with memory effector formation. These results suggest that only recently activated effector T cells can disperse to non-lymphoid sites in the absence of antigen and inflammation, and as effectors return to rest, they lose this ability. These data also argue that memory cells in lymphoid sites are longer lived and not in equilibrium with those in non-lymphoid sites.

Adipose Tissue↗
PubMed1991

Organization of the sea urchin egg endoplasmic reticulum and its reorganization at fertilization.

The ER of eggs of the sea urchin Lytechinus pictus was stained by microinjecting a saturated solution of the fluorescent dicarbocyanine DiIC18(3) (DiI) in soybean oil; the dye spread from the oil drop into ER membranes throughout the egg but not into other organelles. Confocal microscopy revealed large cisternae extending throughout the interior of the egg and a tubular membrane network at the cortex. Since diffusion of DiI is confined to continuous bilayers, the spread of the dye supports the concept that the ER is a cell-wide, interconnected compartment. In time lapse observations, the internal cisternae were seen to be in continuous motion, while the cortical ER was stationary. After fertilization, the internal ER appeared to become more finely divided, beginning as a wave apparently coincident with the calcium wave and becoming most marked by 2-3 min. By 5-8 min the ER returned to an organization similar to that of the unfertilized egg. The cortical network also changed at fertilization; it became disrupted and eventually recovered. DiI labeling allowed continuous observations of the ER during pronuclear migration and mitosis. DiI-stained membranes accumulated in the region of the microtubule array surrounding the sperm nucleus and centriole (the sperm aster) as it migrated to the center of the egg; this accumulation persisted near the centrosomes and zygote nucleus throughout pronuclear fusion and the first two mitotic cycles. We have used a new method to observe the spatial and temporal organization of the ER in a living cell, and we have demonstrated a striking reorganization of the ER at fertilization.

Animals↗
PubMed1993

Studies on the safety of intrasplenic hepatocyte transplantation: relevance to ex vivo gene therapy and liver repopulation in acute hepatic failure.

Hepatocytes transplanted into the host liver engraft promptly, retain normal function, and survive indefinitely. Although intrasplenic transplantation is effective in delivering hepatocytes to the liver, to define potentially limiting complications, we studied its safety in normal, cirrhotic, and partial portal vein-ligated rats. In normal rats, portal pressures increased severalfold after hepatocyte transplantation but returned to normal within 3 weeks. In contrast, in portal hypertensive rats with partial portal vein ligation or cirrhosis, portal pressures were either unchanged or increased less after hepatocyte transplantation. However, more transplanted cells migrated to the lungs along with a rise in right atrial pressures in portal hypertensive rats. Further quantitative studies using 111Indium-labeled hepatocytes showed that intrasplenic retention of transplanted hepatocytes was similar in all animal groups. Intrahepatic cell translocation was comparable in normal and cirrhotic rats, whereas fewer cells migrated to the liver in partial portal vein-ligated rats. The most remarkable difference, however, was significantly greater intrapulmonary translocation of hepatocytes in portal hypertensive rats, which was presumably related to portosystemic shunting. These results indicate that because intrasplenic hepatocyte transplantation induces only temporary portal hypertension in normal subjects, potential strategies to augment liver repopulation could include repeated cell transplantation. This should be useful for optimizing the results of ex vivo gene therapy, or other hepatocyte-based therapies. However, the hepatic and portal hemodynamic status requires careful evaluation in portal hypertensive or cirrhotic subjects if serious complications are to be avoided.

Animals↗
PubMed1997

[Experimental study on injury of the rat nasal mucosa by distilled water irrigation, and its regeneration].

Injuries caused by distilled water and the regeneration process in the nasal mucosa in the respiratory region of the rat were examined electron microscopically and immunohistochemically by light microscopy. The mucosal injury was observed as exfoliation and desquamation of ciliated cells and goblet cells almost everywhere. The basal cells and basal membrane were intact. The regeneration process was completed by the migration, proliferation and differentiation of basal cells. The numbers of nuclear mitotic figures started to increase in a group of rats observed 6 hours after treatment (6-hour group), peaked at 48 hours, and returned to the baseline state after day 4. The BrdU labeling index, on the other hand, started to increase after 6 hours, peaked at 36 hours, and returned to the baseline state after day 4. The goblet cells were predominant even in the 21-day group, compared to the control group. Nuclear mitotic figures and secretory granules were observed together in one cell in the 36-hour group.

Animals↗
PubMed1997

[Pathogenesis of the neuronal migration disorder, with special reference to the animal model of prenatal exposure to low-dose ionizing radiation].

Cortical malformations such as cortical dysplasia and heterotopia constitute the underlying pathology of epilepsy and mental retardation. It is thus important to elucidate the pathogenesis of these migration disorders from the neuropathological viewpoint based upon animal experiments. In this review, I describe the experiment in which low-dose prenatal X-or gamma-irradiation was performed at the mid-gestational period of mice or rats. Low-dose irradiation as low as 150 mGy induced decelerated migration of cortical neurons during the embryonic period together with a changed pattern of cell adhesion molecule, N-CAM. In addition, the effect of radiation remained at least up until 3-week postnatal as disorganized neuronal allocation with respect to the birthdate. With time of further maturation in the neocortex, however, the architecture, in terms of the pattern of distribution of the labeled neurons, returned closely to that found in non-irradiated control animals. Considering the fact that the number of labeled cells per unit cortical area decreased considerably from 3-week to 8-week postnatal, it is conceivable that apoptotic cell death might have occurred in aberrantly placed neurons. Recent progress of molecular genetical approach to human hereditary neurodevelopmental diseases is briefly reviewed, since it greatly contributes to our understanding on the pathogenesis of neuronal migration disorders.

Animals↗
PubMed1979

Effects of antigenic competition between sperm autoantigens and ovalbumin upon humoral and cell-mediated immunity and the development of autoimmune aspermatogenic orchitis (AIAO) in guinea pigs.

The effects of antigenic competition between ovalbumin and sperm autoantigens have been studied in guinea pigs. There was an inhibition of antiovalbumin antibody production up to 60 days after immunization. The cell-mediated immunity against ovalbumin was also depressed at day 30. The simultaneous immunization with both antigens has no effect upon the humoral and cell-mediated immunity against spermatozoa. During the period of inhibition of the humoral and cell-mediated antiovalbumin response, the number of animals developing autoimmune aspermatogenic orchitis was diminished compared to those immunized with spermatozoa alone. Later on, there was no difference between the two groups. The transient inhibition of the immune response against ovalbumin can be explained by the particulate nature of the autoantigens. The sperm cells may be easily trapped by the dendritic reticular cells of the draining lymph nodes. This in turn could affect T cell recognition at early stages, orienting it predominantly toward the sperm autoantigens. At day 90 the situation returned to that present in animals immunized with ovalbumin alone.

Animals↗
PubMed1999

Association of smooth muscle cell phenotypic modulation with extracellular matrix alterations during neointima formation in rabbit vein grafts.

PURPOSE: To clarify the mechanisms of structural changes underlying vein graft stenosis that limits efficacy of bypass grafting operation, we examined the accumulation and distribution of various extracellular matrix (ECM) components during neointima formation in rabbit vein grafts and analyzed their correlation with proliferation and phenotypic modulation of smooth muscle cells (SMCs). METHODS AND RESULTS: An autologous external jugular vein graft was transplanted into the carotid artery in 25 rabbits. After the restoration of blood flow, the graft was markedly dilated. Medial SMCs in the graft appeared to be injured, and they began to proliferate at day 4 and subsequently migrated and formed the neointima at day 7. The neointima observed at days 7 and 14 contained ECM components, including type I collagen, heparan sulfate, and chondroitin sulfate, and the intimal SMCs were phenotypically modulated from the differentiated-type (SM2-positive and SM embryonic-negative) to the dedifferentiated-type (SM2-negative and SM embryonic-positive) as determined with immunostainings for myosin heavy chain isoforms. The intimal SMC proliferation was maximal at 2 weeks and then decreased rapidly. However, the neointima continued to thicken thereafter throughout the 6-month period of the experiment, and ECM accumulation, such as type I collagen and decorin, a small dermatan sulfate proteoglycan, was a prominent feature observed in the hypocellular region of the deep intima from 2 months after the transplantation. The phenotype of the intimal SMCs gradually returned to the differentiated-type from the deep intima after 2 months, but a small number of the intimal SMCs remained in the dedifferentiated phenotype even at 6 months after the operation. CONCLUSION: The neointima in the vein graft was formed initially by means of migration and proliferation of the phenotypically modulated, dedifferentiated-type SMCs and continued to thicken by means of sustained ECM accumulation, including type I collagen and decorin, in association with the prolonged presence of the dedifferentiated-type SMCs. These chronologic features in cell kinetics and ECM accumulation may contribute to the frequent occurrence of graft wall thickening that occurs in the vein grafts.

Animals↗
PubMed1977

Comparison of vascular smooth muscle cells from adult human, monkey and rabbit in primary culture and in subculture.

A method is presented for growing large numbers of pure isolated smooth muscle cells from adult human, monkey, and rabbit blood vessels in primary culture. In the first few days in culture these cells closely resembled those in vivo and could be induced to contract with angiotensin II, noradrenaline and mechanical stimulation. They stained intensely with antibodies against smooth muscle actin and myosin. Fibroblasts and endothelial cells did not stain with these antibodies thereby allowing the purity of each batch of cultures to be monitored. This was consistently found to be better than 99%. The smooth muscle cells modified or "dedifferentiated" after about 9 days in culture to morphologically resemble fibroblasts. At this stage cells could no longer be induced to contract and did not stain with the myosin antibodies. Intense proliferation of these cells soon resulted in a confluent monolayer being formed at which stage some differentiated characteristics returned. The modification of "dedifferentiation" process could be inhibited by the presence of a feeder layer of fibroblasts or endothelial cells, or the addition of cAMP to the culture medium. Smooth muscle cells which had migrated from explants in primary culture, and cells in subculture, had morphological and functional properties of "dedifferentiated" cells at all times. The advantages of differentiated rather than "dedifferentiated" smooth muscle cells in culture for the study of mitogenic agents in atherosclerosis is discussed.

Actins↗