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At least 19 recordsLinked to original sources
PubMed1979

The sensitive period.

A sensitive period exists in humans and experimental animals during which certain visual functions are modifiable by decreased or abnormal visual stimulation. Experiments in monkeys have shown that, at the beginning of this sensitive period, the manifestations of the visual deprivation syndrome develop more rapidly at the cortical than at the geniculate level. Moreover, a shift of cortical dominance as the result of reverse suturing may occur while the geniculate nucleus still reflects the effects of the original deprivation experiment. At the end of the sensitive period the behavioural, electrophysiological, and histological aspects of the visual deprivation syndrome become less predictable. Cortical physiology remains sensitive to abnormal visual input beyond the first 3 months of life. Clinical examples and animal experiments also suggest that the reversal of the effects of visual deprivation may occur long after maturation of the visual system is completed. These findings support the view that abnormal visual stimulation during visual infancy causes a functional reorganization rather than an arrest of development of anatomical retinocortical connections.

Age Factors↗
PubMed1975

Evidence for a sensitive period in the human mother.

In certain animal species immediate separation of a mother from here young for a brief period after deliver (the sensitive period) may result in aberrant maternal behaviour. In the human, disorders of mothering, including child abuse, increase disproportionately in situations associated with early neonatal separation of mother and infant, such as prematurity. Mothers in the United States who were offered early contact with their premature infants showed differences in attachment behaviour when compared with mothers whose first contact with their infants was three weeks after delivery. Mothers who had one hour of close physical contact with their nude full-term infants within the first two hours after delivery and who had 15 extra hours of contact in the frist three days behaved significantly differently during a physical examination of the infant at one month and one year, and in their speech to their infants at two years, from a control group of mothers who had only routine contact. In a similar study in Guatemala, mothers who had 45 minutes of early extra contact showed significantly more attachment behaviour at the time of the first breast-feeding (12 hours). These and other studies in the human suggest that shortly after birth there is a sensitive period which appears to have long-lasting effects on maternal attachment and which may ultimately affect the development of the child.

Auditory Perception↗
PubMed1975

[Active period of genes during Drosophila ontogenesis. I. Temperature-sensitive period for the spineless effect in aristapedia mutants].

The temperature-sensitive period (TSP) was determined for the spineless effect (bristle shortening) in SSa40a mutant of Drosophila melanogaster. The length of front orbital and front vertical bristles was measured at different intervals after the temperature shift from 29 to 17 degrees and vice versa. The TSP was found to last from 7 to 14 hrs during pupal development. This corresponds to the activity of the spineless-aristapedia locus during the period of isolation of bristle initial cells. The discordance between the TSP of spineless effect and that of homoeotic effect of the same gene suggests that the locus SSa40a is activated twice during development.

Alleles↗
PubMed1976

Posthatch age and developmental age as a baseline for determination of the sensitive period for imprinting.

Two experiments comparing developmental age and posthatch age were performed. In the first experiment 143 Peking ducklings of different posthatch ages were imprinted, and their following responses examined in a simultaneous choice test. A sensitive period was evident on the basis of posthatch age. In the second experiment 99 ducklings were separated in three clusters of different posthatch ages, which did not vary within the clusters relative to their probability to be imprinted. The ducklings of each cluster were imprinted at various developmental ages, and the results show the involvement of developmental age. Thus, both experiments considered together favor the concept of an interaction of developmental and posthatch age. Imprinting and the determination of the sensitive period are dependent on prehatch and posthatch learning, so both developmental age and posthatch age are involved in setting the limit of the sensitive period.

Age Factors↗
PubMed1977

[Time of gene activity during drosophila ontogenesis. III. Temperature-sensitive period of the homeotic mutation nasobemia].

The temperature-sensitive period (TSP) was determined for the homoeotic mutation Nasobemia which causes the antenna to leg transformation in D. melanogaster. The rate of homoetic transformation was measured in the adult flies which emerged after the temperature shift from 29 to 17 degrees and vice versa applied at different larval stages. The TSP begins at 29 degrees at 63 hrs and ends at 39 hrs prior to the pupation, while at 17 degrees it begins at 216 hrs and ends at 132 hrs prior to the pupation. This means that the end of the 1 st larval instar and practically all the 2nd instar are temperature sensitive. A suggestion is put forward to the effect that the TSP corresponds to the period during which the process of abnormal determination of the imaginal disc cells takes place.

Animals↗
PubMed1975

Rubella cataract in vitro: Sensitive period of the developing human lens.

The clinically known sensitive period of rubella cataract was studied in vitro by infecting 79 human eye rudiments from embryos aged 4-10 wk with rubella virus. The course of the infection was followed by histological and indirect immunofluorescence methods. Of the rudiments, 12 pairs were in the lens placode or open-lens-vesicle stage, 40 already had closed lens vesicles and in another 27 closed-stage pairs an incision was made in the lens capsule before infection to allow the virus to enter the lens. Uninfected controls differentiated well in vitro for 4-6 wk. The eye rudiments infected in the open-lens-vesicle stage showed lens fiber destruction and viral antigens within the lens. No damage or viral antigens were detected in rudiments infected in the closed stage unless the lens capsule was incisedmwhen this was done, however, fiber damage ensued and viral antigens appeared. The lens capsule was concluded to form a protective barrier around the sensirive fibers at the time of closure of the lens vesicle, confirming the earlier hypothesis and clinical findings.

Antigens, Viral↗
PubMed1992

Stimulation of in vitro steroidogenesis by pituitary hormones in a turtle (Trachemys scripta) within the temperature-sensitive period for sex determination.

To investigate the possible involvement of pituitary hormones in the regulation of steroidogenesis during reptilian sexual differentiation, we tested the ability of gonadotropin (ovine FSH), adrenocorticotropin (porcine ACTH), and growth hormone (bovine GH) to stimulate in vitro steroidogenesis in embryonic adrenal-kidney-gonad complexes (AKGs) of a turtle, Trachemys scripta, during and after the temperature-sensitive period for sex determination (TSP). Radioimmunoassays were used to measure progesterone, testosterone, estradiol, and corticosterone in incubation media; additionally, immunoreactive ACTH was measured in plasma. Presumptive male and female AKGs were stimulated by both FSH and ACTH at each stage investigated. Secretion of progesterone and corticosterone was usually far greater than that of testosterone or estradiol in both basal and hormone-stimulated incubations. In general, AKGs from presumptive males secreted more progesterone and corticosterone than AKGs from presumptive females. Progesterone and estradiol secretions were stimulated by both FSH and ACTH, but testosterone secretion was stimulated only by ACTH. Corticosterone secretion was strongly stimulated by ACTH. GH failed to significantly stimulate steroid secretion. Plasma ACTH levels were significantly higher in males than in females, and both sexes had significantly higher plasma levels of ACTH after the TSP compared to during the TSP. Our data demonstrate that during the temperature-sensitive period AKGs are responsive to both gonadotropin and ACTH, and that there are significant sex differences in steroidogenesis, sensitivity to gonadotropin and ACTH, and plasma ACTH levels.

Adrenocorticotropic Hormone↗
PubMed1992

Clinical evidence for the onset of the sensitive period in infancy.

Seven neonates had a IIIrd or VIth nerve palsy or afferent visual pathway pathology at birth. These abnormalities resolved within 6 weeks and the children have developed normal visual acuity, motor fusion, and stereopsis. We conclude that there is a latent period of 6 weeks before the onset of the sensitive period.

Abducens Nerve↗
PubMed1977

Increase of the corticosterone level in ducklings during the sensitive period of the following response.

Increased fear may be one of the factors limiting the sensitive imprinting period. Thus, we analyzed corticosterone levels in 121 Peking ducklings during and after this sensitive period using the method of competitive protein binding. The data pointed to a corticosterone increase within a period of 12-28 hr after hatching as well as to the presence of a circadian rythm. The low coefficient of determination of post-hatch age and corticosterone level (8%) pleads for a multi-dimensional system. However, the corticosterone increase may be the basis for an increase in fear and a decrease in the likelihood of imprinting.

Age Factors↗
PubMed1976

[Time of gene activity in ontogenesis of Drosophila. 2. Temperature-sensitive period of SSa-40a mutation in Drosophila melanogaster].

In the mutants aristapedia (ssa-40a) of D. melanogaster, the temperature-sensitive period (TSP) was determined for the effects observed in the thoracic legs (fusion of tarsal segments). The TSP began in the middle of the first and finished in the end of the second quarter of the 3rd larval instar. The TSP for ssa-40a overlapped the TSP for homoeotic transformation of aristae into tarsi but did not overlap the TSP for spineless effects. An attempt is undertaken to consider the state of determinantion on the basis of the hypothesis of autogenous regulation of gene activity.

Alleles↗
PubMed2026

Sensitive periods for prenatal alcohol exposure shape internalizing symptoms across development.

IMPORTANCE: Prenatal alcohol exposure (PAE) is associated with lasting cognitive and neurodevelopmental deficits and can quadruple risk for depression later in life. However, it remains unknown whether there are specific trimesters when PAE is more strongly associated with longitudinal trajectories of internalizing symptoms - an indicator of depression risk - across childhood and adolescence. OBJECTIVE: To investigate how PAE timing and dosage are associated with internalizing symptom trajectories from ages 4 to 16.5 years. DESIGN SETTING AND PARTICIPANTS: We analyzed prospective data from the Avon Longitudinal Study of Parents and Children (ALSPAC), an ongoing longitudinal birth cohort from the United Kingdom. Internalizing symptom trajectories were estimated for 6,409 participants. Primary analyses were conducted on 2,254 participants with complete data on PAE in all three trimesters, covariates, and trajectories. MAIN OUTCOMES AND MEASURES: We used growth mixture modelling to identify latent trajectories of depressive symptoms measured using the internalizing symptom scale from the Strengths and Difficulties Questionnaire (SDQ) at seven occasions between ages 4 to 16.5 years. Prospective alcohol consumption during each trimester were categorized into three PAE dosages: unexposed (0 drinks/week), low (1-7 drinks/week) and high (7+ drinks/week). RESULTS: We identified five distinct depressive symptom trajectories: stable low (75.9% of participants), moderate childhood peak (11.2%), progressive increase (5.57%), high early childhood (4.73%), and early adolescent peak (2.61%). PAE in the second (relative risk [RR]=2.08, 95% CI=1.15-3.76) and third trimesters (RR=1.83, 95% CI=1.05-3.21), as well as total PAE burden across pregnancy (RR=1.33, 95% CI=1.06-1.68) increased risk for the progressive increase trajectory, versus the stable low trajectory. High PAE in the second (RR=2.71, 95% CI=1.41-5.21) and third (RR=2.27, 95% CI=1.27-4.05) trimesters drove elevated risk for this trajectory. PAE in the first trimester or at low dosages showed no associations with depressive symptom trajectories. Negative control analyses of paternal drinking also found no associations. CONCLUSIONS AND RELEVANCE: Our results highlight the second and third trimesters as potential sensitive periods for the impact of PAE on rising depressive symptoms from childhood to adolescence. Ultimately, these findings could inform the design of prevention programs, and facilitate targeted interventions to youth at elevated risk for depression.

ALSPAC↗
PubMed1992

Sensitive period for the induction of endoreduplication by rotenone in cultured Chinese hamster cells.

Rotenone-induced endoreduplication was investigated in Chinese hamster CHL cells. Cell cycle analyses, using 5-bromo-2'-deoxyuridine (BrdU) labeling, revealed that endoreduplication was induced between the G2-phase and mitotic metaphase. Morphological studies indicated that the chromosomes of cells in metaphase at the time of rotenone exposure immediately aggregated. Within 1 h, however, the aggregated chromosomes began to decondense forming telophase nuclei. Cells with aggregated chromosomes were collected by mitotic selection using the mitotic arrestant TN-16 and then cultured for 30 h following rotenone administration. This population of cells demonstrated an extremely high frequency of endoreduplicated metaphases. Further analysis by BrdU labeling indicated that the aggregated metaphases underwent only one round of DNA replication before endoreduplicated metaphases were formed. The most sensitive period for the induction of endoreduplication by rotenone occurs during mitotic metaphase.

Animals↗
PubMed1979

Delineation of the glucocorticoid-sensitive period of intestinal development in the rat.

Jejunal sucrase has been used as a marker for intestinal development. The effects of sequential adrenalectomy and sequential administration of hydrocortisone have led to the conclusion that the glucocorticoid sensitivity of the jejunum ceases abruptly at a postnatal age of 17--18 days. Adrenalectomy on day 17 or earlier resulted in significant depression of the usual developmental rise of sucrase activity, whereas adrenalectomy on days 18, 21, or 28 or in adults had no effect on sucrase activity. In contrast, the effect of adrenalectomy on body weight was similar to all ages studied. When hydrocortisone (50 microgram/g BW) was administered to intact animals on day 15 or 16, it caused significant elevation of sucrase activity but, when administered on day 17, 18, or 28, there was no difference between control and treated animals. Since adrenalectomy on day 15 delayed weaning, it was possible that the glucocorticoid dependence of the younger animals was mediated by effects on feeding behavior. However, a further study showed that complete prevention of weaning did not depress sucrase activity between days 15--21. Thus, at early ages, when the tissue was sensitive to glucocorticoid, it was independent of dietary regulation. In contrast, at later ages (days 25 and 27), prevention of weaning caused significant depression of jejunal sucrase activity.

Adrenalectomy↗
PubMed1991

A periodate-sensitive anti-phagocytic surface structure, induced by growth in milk whey, on Staphylococcus aureus isolated from bovine mastitis.

The phagocytic and chemiluminescent activity of purified bovine neutrophils in response to two Staphylococcus aureus strains isolated from mastitic bovine milk and grown in milk whey was studied. The activity was significantly reduced compared with the response elicited by the same strains grown in tryptic soy broth (TSB). A mild periodate treatment of the milk whey-grown strains resulted in a significant increase of both chemiluminescence and phagocytosis, whereas trypsin, subtilisin or papain treatment had no effect. The decreased binding of complement factor C3 to milk-whey-grown bacteria was restored to the level of TSB-grown homologous organisms by periodate treatment. Moreover, this treatment, but not treatment with trypsin, increased the surface hydrophobicity of milk-whey-grown bacteria. The chemiluminescent activity was as high towards heat-killed as towards live bacteria. Also, incubation of heat-killed TSB-grown bacteria in milk whey did not alter the chemiluminescent response, indicating that the reduced neutrophil activity towards milk-whey-grown bacteria was not due to binding of milk components to the microorganisms. These results strongly suggest that bovine mastitis S. aureus strains grown in milk whey produce an anti-phagocytic surface structure. This structure is heat- and protease-resistant and renders the bacterial surface hydrophilic. The anti-phagocytic material is altered or, more likely, released from the bacterial surface on periodate treatment and is probably of carbohydrate nature.

Animals↗
PubMed1975

Actinomycin D-sensitive periods in the differentiation of Drosophila neurons and muscle cells in vitro.

Observations were made of neuroblasts differentiating into neurons, and myoblasts differentiating into myocytes in cultures of embryonic Drosophila cells. Axons greater than 50 mum long appeared in vitro between 7.5 and 16.5 h, and pulsating myocytes appeared between 12.5 and 23.5 h. Actinomycin D treatment prevented neuroblasts and myoblasts from proceeding in differentiation. Neurons became resistant to actinomycin D when they reached the stage of axon initiation, and axon elongation was not actinomycin D-sensitive. Myocytes were sensitive to actinomycin D until they attained the ability to pulsate, and ongoing pulsations were not halted by the drug. Autoradiographs and controls indicated that actinomycin D prevented uridine incorporation by about 90% but prevented leucine and thymidine incorporation by 6% or less in these cells. The result favour the interpretation that transcription is necessary in neuron differentation up to the point of axon initiation and in myocytes up to the point where pulsations can begin. Since ribosomal RNA synthesis is unnecessary for these differentiations, necessary RNA synthesis would be messenger or transfer RNA, or RNA of unknown identity.

Animals↗
PubMed1992

Testicular masculinization of vocal behavior in juvenile female Xenopus laevis reveals sensitive periods for song duration, rate, and frequency spectra.

In Xenopus laevis, adult males but not females produce courtship songs comprised of rapid trills. Two experiments were conducted to determine whether male-typical singing could be induced in females. At 6 different juvenile stages, male and female frogs were gonadectomized and implanted with testes, grown to sexual maturity, and tested for vocal behavior. All frogs with functional testicular implants sang; females sang as much as males. The frequency spectra of the clicks within trills were fully masculinized in females implanted at PM0, PM1, and PM2. There were deficiencies in song quality in females implanted late in juvenile life. Females receiving testis implants at PM3, PM4, and PM5 did not produce clicks with masculine spectral qualities. In a concurrent experiment, adult males and females were gonadectomized and implanted with testes or silicone tubes containing testosterone propionate. When tested for vocal behavior 10 to 15 months after implantation, 8/10 androgen-treated males, 3/12 androgen-treated females, 5/5 testes-implanted males, and 2/4 testes-implanted females sang. The females that did sing spent much less time singing than males. The click rates of females were uniformly slower than males and no female produced clicks with a masculine frequency spectrum. Thus, testicular secretions can induce male-typical singing in females until late in juvenile development. However, females exhibit a progressive decline in vocal potential with increasing age, culminating in an almost complete loss of singing ability by adulthood.

Acoustic Stimulation↗