Biomedical subjects

B Xu

Publications and source records attributed to B Xu.

At least 253 records · Page 14Linked to original sources

PubMed1996

Prenatal prediction of neonatal growth status in twins using individualized growth assessment.

OBJECTIVE: To determine if the growth status at birth of twins can be predicted in the third trimester using the Prenatal Growth Assessment Score (PGAS). METHODS: The growth of 40 twin fetuses were studied with ultrasound from 14 weeks until delivery. Measurements of the head circumference (HC), abdominal circumference (AC), thigh circumference (ThC), femur diaphysis length (FDL), head cube (A), and abdominal cube (B) were made at 2 to 3 week intervals. Rossavik growth models for these parameters were determined from second trimester measurements. These models were used to define expected third trimester growth curves and birth characteristics. Comparisons of expected and actual third trimester measurements were used to calculate PGAS values after various time points (PGASAt) and after the last time point (PGASAT). Similar comparisons after birth were used to determine Growth Potential Realization Index (GPRI) values for HC, AC, ThC, weight (WT), and crown-heel length (CHL), with and without correction for decreased soft tissue deposition. These two sets of GPRI values were used to calculate two sets of Neonatal Growth Assessment Scores (NGASS, NGASTw). Using NGASS and NGASTw (as well as GPRI values in some cases), the twin neonates were classified as Normal (N), Decreased Soft Tissue Deposition, (DSTD), Intrauterine Growth Retardation (IUGR) and Macrosomia (M). RESULTS: At birth 22/40 (55%) were classified as N, 9/40 (22.5%) as DSTD, 6/40 (15.0%) as IUGR, and 3/40 (7.5%) as M. All -PGASAT values in the N group were greater than -0.40% with one exception (-PGASAT = -0.43%). All PGASAt values were above this same boundary except for one fetus. No differences were seen between the N and DSTD groups [mean -PGASAT (range): N, -0.12% (0% to -0.34%); DSTD, -0.10% (0% to -0.30%)]. The IUGR group had 4 fetuses with -PGASAT values between -0.65% and 2.79% and two with values of 0.0% and -0.12%. Growth retardation in the latter two was limited to a decrease in thigh soft tissue deposition. -PGASAt values in the first 4 fetuses were below -0.40% 1.6 to 9.5 weeks before delivery (mean: 6.1 weeks). Fetuses in group M had +PGASAT values of 0.0%, +1.8%, and +1.2%. PGASAt values were above +0.40% at 3.6 and 9.8 weeks before delivery in the latter two fetuses. CONCLUSIONS: These results support the concept that PGASAT and PGASAt values outside +/- 0.40% indicate either IUGR or macrosomia. Almost all fetuses with growth problems in the third trimester can be detected, on average, 6 weeks before delivery unless the growth abnormality is limited to decreased soft tissue deposition.

Anthropometry↗

PubMed1996

Flowable networks as DNA sequencing media in capillary columns.

A novel class of materials that self-assemble in water into equilibrium network structures with a well-defined mesh size consist of polyethylene glycols (PEG's) end-capped with micelle-forming fluorocarbon tails. These micellar systems form flowable aqueous gel-like networks that permit electrophoretic DNA sequencing in capillary columns. The gels have unusual rheological properties, including network breakdown under shear, resulting in plug flow that allows columns refill with complete ejection of byproducts of the previous sequencing analysis. In this system, DNA fragment electrophoretic mobilities are unaffected by the hydrophobicity of the polymer tails. Low molecular weight (M) PEG chains (M 8000) show catastrophic resolution loss for DNA fragments larger than 100 bases due to band broadening. For a longer PEG segment (M 35000) separating the end groups, band broadening occurs for DNA fragments larger than 300 bases, implying that the PEG segment length controls the mesh size in the equilibrium network structure. Optimum sequencing results were obtained from a 6% solution of a 1:1 mixture of C6F13 end-capped- and C8F17 end-capped PEG 35,000. The resolution limit of fluorescent-dye-labeled sequencing products in this formulation was 450 bases in 75 microns capillaries at 200 V/cm.

Base Sequence↗

PubMed1996

Gene conversion and homologous recombination in murine B cells.

Gene conversion has been found to be important in the diversification of antibody genes in chickens and in rabbits. In other species, however, it is not clear whether gene conversion plays any role in antibody diversity. Analysis of an H-chain antibody gene construct that was designed to optimize the detection of gene conversion events in transgenic mice has shown that sequence transfers that resemble gene conversion events can occur in murine B cells and are associated with somatic hypermutation. This raises the possibility that an error-prone gene conversion mechanism might play a role in murine somatic hypermutation.

Animals↗

PubMed1996

Unequal potency of transgenic yeast hexokinase on pancreatic beta cell metabolism and secretion.

Recent reports have proposed that sequence specific interactions between glucokinase and other beta cell proteins are important to glucokinase regulation of beta cell activity. We have previously reported enhancement of beta cell function by a transgenic hexokinase derived from yeast which has only 30% amino acid sequence homology to glucokinase. To test the functional significance of the amino acid sequence of islet glucokinase we have made a quantitative study of the effect of yeast hexokinase on beta cell glucose metabolism and insulin secretion. Transgenic and normal islets were assayed for hexokinase activity, glucose usage and insulin secretion. Most parameters were measured at six glucose concentrations between 0.5 and 20 mM glucose. Transgenic islet hexokinase activity measured in islet extracts exceeded normal islet hexokinase activity by 31 to 77 percent at different glucose concentrations. At all glucose concentrations tested the percentage increase in transgenic glucose metabolism greatly exceeded the percentage increase in transgenic hexokinase activity. The increase in transgenic glucose metabolism produced a proportional reduction in the threshold for glucose stimulated insulin secretion. However, yeast hexokinase had little if any effect on the first phase of insulin secretion. The finding that metabolism was very sensitive to yeast hexokinase but first phase secretion was not, supports recent proposals that hexokinase and glucokinase may be physically and functionally separated in the beta cell.

Amino Acid Sequence↗

PubMed1996

A simple filtration method to remove plankton-associated Vibrio cholerae in raw water supplies in developing countries.

Plankton to which cells of Vibrio cholerae O1 and/or O139 were attached was introduced into 0.5% Instant Ocean microcosms maintained at 25 degrees C. The bulk of the plankton and associated particulates was removed with a filter constructed from either nylon net and one of several different types of sari material, the latter being very inexpensive and readily available in villages in Bangladesh, where V. cholerae is endemic. V. cholerae was enumerated before and after filtration to evaluate the efficiency of the filtration procedure. The results obtained indicate that 99% of V. cholerae, i.e., those cells attached to plankton, were removed from the water samples. Epidemic strains of V. cholerae O1 and O139 from various geographical sources, including Bangladesh, Brazil, India, and Mexico, were included in the experiments. Removal of vibrios from water by this simple filtration method was found to yield consistent results with all strains examined in this study. Thus, it is concluded that a simple filtration procedure involving the use of domestic sari material can reduce the number of cholera vibrios attached to plankton in raw water from ponds and rivers commonly used for drinking. Since untreated water from such sources serves as drinking water for millions of people living in developing countries (e.g., Bangladesh), filtration should prove effective at reducing the incidence and severity of outbreaks, especially in places that lack fuel wood for boiling water and/or municipal water treatment plants. The results of this study provide the basis for determining such reductions, which are to be carried out in the near future.

Animals↗

PubMed1996

Serogroup conversion of Vibrio cholerae non-O1 to Vibrio cholerae O1: effect of growth state of cells, temperature, and salinity.

Recently, we reported the occurrence of seroconversion from Vibrio cholerae non-O1 to V. cholerae O1, but little is known about the environmental and physiological factors influencing seroconversion. We investigated effects of temperature (4, 25, and 35 degrees C) and salinity ( < 0.05 and 10%0.), as well as the stage of growth of cells, on serogroup conversion. Seroconversion of V. cholerae occurred under various environmental conditions. However, the rate of seroconversion in natural water ( < 0.5% salinity) and synthetic seawater microcosms (10%0 salinity), employing cells harvested from stationary phase culture, was approximately 2 logs higher than cells harvested from cultures in the logarithmic phase (i.e., 10(5) versus 10(3) per 10(10) cells. Thus, the physiological state of the cells, and to a lesser degree, temperature and salinity, is an important factor in the conversion of V. cholerae from non-O1 to O1 serogroup.

Antigens, Bacterial↗

PubMed1996

Induction of human myeloblastic ML-1 cell G1 arrest by suppression of K+ channel activity.

Our previous studies have shown that a voltage-gated K+ channel is highly expressed in proliferating human myeloblastic ML-1 cells and is suppressed in the early stages of 12-O-tetradecanoylphorbol-13-acetate-induced ML-1 cell differentiation. In the present study, we report that inhibition of the K+ channel activity by 4-aminopyridine (4-AP) suppressed ML-1 cell proliferation, as measured by DNA synthesis. Cell cycle mapping indicated that ML-1 cells were arrested in G1 phase after 24-h treatment with 4-AP. Blockade of ML-1 cells at the G1/S boundary of the cell cycle with aphidicolin revealed that ML-1 cells past the G1 checkpoint were capable of entering S phase and synthesizing DNA independently of the channel blockade. ML-1 cell differentiation, measured by CD14 marker protein expression, revealed that the effect of 4-AP was to cause growth arrest and that it did not cause differentiation. Dephosphorylation of retinoblastoma protein accompanied inhibition of ML-1 cell proliferation and suggested that suppression of K+ channel activity by 4-AP is associated with retinoblastoma protein-mediated G1 arrest in ML-1 cells. Moreover, we found that ML-1 cell volume increased 35 +/- 7% after 4-AP treatment, which could be an early event triggering inhibition of ML-1 cell proliferation. These findings suggest that a 4-AP-sensitive K+ channel may play an important role in the transduction of mitogenic signals in ML-1 cells.

4-Aminopyridine↗

PubMed1996

Disinhibition from opioid influence augments hypothalamic neuropeptide Y (NPY) gene expression and pituitary luteinizing hormone release: effects of NPY messenger ribonucleic acid antisense oligodeoxynucleotides.

It is well known that hypothalamic endogenous opioid peptides (EOP) exert an inhibitory influence on LH release, and that a restraint on this inhibitory tone triggers preovulatory LHRH and LH hypersecretion. Recent evidence suggests that hypothalamic neuropeptide Y (NPY) is an important component of the neural circuitry that participates in induction of the LH surge. We have reported previously that blockade of EOP influence by the opioid receptor antagonist, naloxone (NAL), stimulated NPY accumulation in the median eminence (ME) in association with increased LH release in estradiol-17 beta-primed ovariectomized rats. To evaluate whether a restraint on the EOP system will result in an increase in NPY synthesis, the effects of NAL infusion on preproNPY messenger RNA (mRNA) levels in the medial basal hypothalamus were studied by solution hybridization/RNase protection assay and by in situ hybridization. NAL (2 mg/0.6 ml.h) or saline (SAL, 0.6 ml/h) was infused for 3 h (1100-1400 h) via an intrajugular cannula in estradiol-17 beta-primed ovariectomized rats. In accord with previous studies, NAL infusion significantly increased plasma LH levels at 1400 h. concomitant with this activation of LH release, NPY gene expression was also augmented. As compared with initial control levels at 1100 h, preproNPY mRNA levels in the medial basal hypothalamus increased at 1400 h in SAL (106%)- and NAL (202%)-infused rats, and at this time, preproNPY mRNA levels were significantly higher in NAL-infused rats than in SAL-infused rats. In situ hybridization studies showed that NAL infusion significantly increased the preproNPY mRNA signal at 1400 h mainly in the rostral and middle regions of the arcuate nucleus (ARC) as compared with that seen at 1100 and 1400 h in SAL-infused rats. To examine further the relationship between the NAL-induced increase in LH release and increase in NPY gene expression, the effects of NPY mRNA antisense oligonucleotides (oligos) on NPY levels in the ME-ARC and on plasma LH levels were studied in NAL-infused rats. In NAL-infused rats, intracerebroventricular administration of a NPY antisense oligo (25 micrograms/rat) at 1000, 1200, and 1300 h decreased NPY levels in the ME-ARC and blocked the increase in plasma LH levels at 1500 h, whereas control missense oligos had no effect. Collectively, these results show that a decrease in opioid influence rapidly augments NPY gene expression in a subpopulation of neurons in the ARC, and support the hypothesis that a disinhibition from opioid influence acutely promotes NPY synthesis and release, which is necessary for phasic LH discharge in rats.

Animals↗

PubMed1996

An interactive physiological role of neuropeptide Y and galanin in pulsatile pituitary luteinizing hormone secretion.

Both neuropeptide Y (NPY) and galanin (GAL) systems have been implicated in the excitatory regulation of pulsatile LH secretion in the ovariectomized rat. The present studies were designed to examine the possible interaction of these two neuropeptides in controlling episodic LH release by testing the effects of central infusion of antibodies (Ab) to NPY and GAL, alone or in combination; additional studies tested the effects of central administration of an antisense oligodeoxynucleotide (ODN) to NPY and GAL messenger RNA. Rats were ovariectomized, implanted with a cannula in the third ventricle, and used in experiments 2 weeks later. Central infusion, via Alzet osmotic minipumps, of IgG purified from an NPY Ab produced a dose-related suppression of pulsatile LH secretion. Although an Ab dilution of 1:10 was ineffective, a maximal inhibitory effect was obtained using an NPY Ab dilution of 1:1, which decreased the mean levels, pulse frequency, and pulse amplitude of LH. These parameters of episodic LH secretion were also significantly reduced by central injection of antisense NPY ODN compared to those in vehicle- or missense ODN-treated controls. Similar dose-related inhibitory effects on the parameters of LH secretion were seen after central infusion of GAL Ab. Furthermore, infusion of a combination of NPY Ab and GAL Ab, each at the ineffective dilution of 1:10, resulted in a profound inhibition of LH secretion equivalent to the pattern seen with the maximally effective 1:1 Ab dilution. These results strengthen the idea of a physiological role for both NPY and GAL systems in the mechanism underlying the LHRH pulse generator activity and further suggest that these two excitatory neuropeptides act in concert to generate pulsatile LHRH release.

Animals↗

PubMed1996

Evidence that gonadal steroids modulate nitric oxide efflux in the medial preoptic area: effects of N-methyl-D-aspartate and correlation with luteinizing hormone secretion.

Several lines of evidence suggest that nitric oxide (NO) is involved in the neuroendocrine control of reproductive function. This study was undertaken to determine 1) NO activity in the medial preoptic area (MPOA) where LHRH- and NO synthase-containing neurons are coextensive; 2) whether N-methyl-D-aspartate (NMDA) receptor activation, which stimulates LHRH release, augments NO activity in the MPOA; and 3) whether NO activation in the MPOA underlies the steroid dependency of NMDA-induced pituitary LH release. As extracellular levels of cGMP in discrete brain sites are a reliable index of basal and stimulated activity of NO, extracellular cGMP levels in the MPOA of freely moving, awake rats were measured by microdialysis in the current study. In the first experiment, the MPOA of intact and castrated male rats were microdialyzed with artificial cerebrospinal fluid at a rate of 5 microliters/min. The basal level of cGMP efflux was determined from the initial seven samples collected at 20-min intervals. The NO response to a single i.v. injection of NMDA (10 mg/kg) or saline was assessed in the next five samples. In the second experiment, the basal and NMDA-evoked NO effluxes in the MPOA of ovariectomized (ovx) and estrogen-treated ovx rats were examined. Results showed that in both sexes, the absence of gonadal steroids resulted in significantly lower basal cGMP levels. Additionally, the cGMP response to NMDA was steroid dependent. Whereas in castrated rats it failed to affect cGMP efflux, NMDA in intact male rats promptly raised cGMP levels at 20 min, and these elevated levels were maintained through the duration of the experiment. This NMDA-induced cGMP response, observed selectively in intact rats, was also associated with stimulation of plasma LH levels. In female rats, NMDA similarly enhanced MPOA cGMP efflux and pituitary LH secretion in estradiol benzoate-treated, but not in oil-treated, ovx rats. The NMDA receptor antagonist D,L-amino-5-phosphoropentanoic acid and the NO synthase inhibitor, N omega-nitro-L-arginine, completely blocked the NMDA-induced cGMP and LH responses, thereby demonstrating the specificity of the NMDA receptor --> NO line of communication probably operating in the MPOA in the control of pituitary LH release. Therefore, these results show that gonadal steroids augment basal as well as NMDA-induced MPOA cGMP efflux in male and female rats. It is likely that facilitation of NO/cGMP activity in the MPOA may underlie the steroid dependency of NMDA-evoked LH hypersecretion in the rat.

2-Amino-5-phosphonovalerate↗

PubMed1996

Factors influencing the response to interferon therapy in chronic hepatitis C. Studies on viral genotype and induction of 2',5'-oligoadenylate synthetase in the liver and peripheral blood cells.

BACKGROUND: The mechanism behind the antiviral action of interferon (IFN) therapy in chronic hepatitis C virus (HCV) infection is not well understood, and, furthermore, few factors have been shown to be good predictors of a favourable response to IFN treatment in chronic HCV infection. METHODS: Freshly explanted liver cells and peripheral blood mononuclear cells (PBMC) from 80 patients with chronic HCV infection were used to study the capacity of IFN to induce the enzyme 2',5'-oligoadenylate synthetase (2'5'-AS) in vitro. The HCV genotype was determined in 53 patients. The induction of 2'5'-AS was correlated to the results of IFN-alpha treatment in 36 patients. RESULTS: Normalization of transaminases during IFN treatment was significantly associated with 2'5'-AS levels in liver cells cultured in the absence of IFN. A similar tendency, although not statistically significant, was found for IFN-induced levels of 2'5'-AS in liver cells. No such associations were found when PBMC were analysed. Six patients showed a sustained biochemical response. These six did not deviate significantly from the remaining patients with regard to base-line or IFN-induced levels of 2'5'-AS in liver cells or PBMC. Eradication of HCV RNA during IFN treatment did not correlate with 2'5'-AS levels in liver cells. Comparison of HCV genotype and clinical response showed that patients with genotype 3a had the most favourable outcome. No association was found between liver histology and treatment outcome. CONCLUSION: These data imply that direct effects of IFN on liver cells are of importance for the response to IFN treatment.

2',5'-Oligoadenylate Synthetase↗

PubMed1996

Morphological and ultrastructural changes induced in corneal epithelial cells by HIV-1 and HHV-6 in vitro.

PURPOSE: The purpose of this study was to determine whether HIV-1 and HHV-6 are capable of infecting and inducing morphological and ultrastructural changes in corneal epithelial cells in vitro. METHODS: Primary and transformed corneal epithelial cell cultures were infected with HIV-1 or HHV-6 in vitro and analyzed for the presence or absence of viral antigens, DNA sequences, viral particles and inclusions. RESULTS: HIV-1 antigens were detected in 8% of the HIV-1 infected cells and early HHV-6 antigens were present in 12% of the HHV-6 infected cells. The presence of viral DNA sequences in the cultures confirmed these findings. Cells infected with HIV-1 morphologically were not different from uninfected cells, whereas the morphology of HHV-6 infected cells was very similar to cells infected with other human herpesviruses. Cytoplasmic tubuloreticular inclusions were detectable in corneal epithelia cells infected with HIV-1 and intact viral particles were visible only in PBMC used to recover HIV-1 from these cultures. Viral inclusions were also observed in corneal epithelial cells infected with HHV-6. CONCLUSION: These data indicate that HIV-1 and HHV-6 are capable of infecting corneal epithelial cells in vitro, but the viruses are not entering these cells via CD4 or galC receptors. This basic information is important in determining the pathogenic mechanism(s) involved in the development of AIDS-associated corneal disorders.

Antigens, Viral↗

PubMed1996

[Management of anterior vitreous by high gluey Healon].

PURPOSE: To investigate the technique of managing anterior vitreous by high gluey Healon. METHODS: In 15 eyes of 15 cases having undertaken in situ phacoemulsification vitreous loss, 12 eyes of 12 cases in ECCE, 3 eyes of 2 cases in Marfan Syndrome, 13 eyes of 13 cases in eye injury, tunnel incision was made and PC-IOL implantation was performed after high gluey Healon managing anterior vitreous on all the cases. RESULTS: High gluey Healon managing anterior vitreous in 43 eyes, post capsule injuries was not enlarge, and cortex or fragments of len nuclear not fall in vitreous cavity. Visual acuity of 0.5 or better at postoperative one week were 72.1% and 59.1% respectively. CONCLUSION: The technique of managing anterior vitreous by high gluey Healon was worthy to be spread due to minimum injury, vitreous loss, and fast restoration of visual acuity.

Adolescent↗

PubMed1996

[Effect of kanggusong in prevention and treatment of retinoic acid induced osteoporosis in rats].

Retinoic acid 70 mg/kg.d was given by gastrogavage to Wistar rat for 14 days to induce osteoporosis. Kanggusong (KGS), a mixture of extracts from 8 traditional Chinese drugs, was given to 3 test groups of rats simultaneously in various dosage. Results showed that the KGS displayed obvious action in preventing osteoporosis, the trabecular loss of tibiae and bone loss of compact bone were lowered markedly in KGS groups with high (3.0 g/kg.d) or middle (1.0 g/kg.d) dosage in comparing with control model group, the trabecular area percentage and compact bone area percentage were increased significantly (P < 0.05) which approached to the level of normal control group. KGS could also improve the pathological changes in microstructure of bone, increase the thickness of trabecula and cortex (P < 0.05), reduce the trabecular gap and bone marrow cavity (P < 0.05). The mechanism of KGS might be relevant with its action of suppressing the osteoclast activity and activating osteoblast, resulting a positive balance of bone metabolism, increasing the blood concentration of calcium and estrogen as well as its antagonistic action against the injury of sex glands by retinoic acid.

Animals↗

PubMed1996

[A clinical report on mixed astigmatism].

OBJECTIVE: This study was designed to analyze the common cause of asthenopia, mixed astigmatism. METHODS: The types and characters of mixed astigmatism in 356 eyes (207 patients) were analyzed and their naked and corrected visual acuities were investigated. Some problems of mixed astigmatism were discussed. RESULTS: Most of the patients had evident visual defects, the average naked visual acuity being 0.3 (20/60). However, all the patients had better corrected visual acuities with an average of 0.6 (20/30). CONCLUSIONS: Due to the presence of accommodation during the examination, an incorrect lens may be prescribed. Three mistakes might occur, (1) A mixed astigmatism is not detected, and a simple myopic lens is prescribed; (2) An eye with mixed astigmatism is diagnosed as simple or compound myopic astigmatism; (3) A hyperopic astigmatism is diagnosed as mixed astigmatism. The visual defects caused by mixed astigmatism can be satisfactorily corrected by spectacles.

Adolescent↗

PubMed1996

[A model of osteoporosis induced by retinoic acid in male Wistar rats].

An animal model of osteoporosis induced by retinoic acid was successfully established in 3-month-old male Wistar rats. The animals were given the drug 70 mg.kg-1.d-1 for 14 d intragastrically and sacrificed on day 29. The proximal tibia and middle tibia of the rats were processed undecalcifiedly for quantitative bone histomorphometry. Compared with the control rats, the cancellous and compact bone volume of the model rats were reduced markedly. The bone tissue microstructure showed some obvious pathological changes that the trabecular number were decreased, the separation of trabecular and medulla ossium cavity became large, the thickness of trabecular and cortex of bone were decreased. The mechanism of bone loss in the model rats was that the osteoclast was activated by retinoic acid which promoted bone resorption. Other changes in the model rats were also observed such as: the body weight, and the weights of seminal vesicle and prostate were decreased, the adrenal glands and spleen showed hyperplasia and hypertrophy. No change of the blood concentration of calcium, phosphorus, alkaline phosphatase, alanine transaminase, estradiol and testosterone in the model rats was observed.

Animals↗

PubMed1996

[Oral contraceptive and risk of disease].

OBJECTIVE: To study the risk and benefits of using compination-type oral contraceptives (COC) for diseases. METHOD: Meta-analysis was used to estimate the summary relative risk (SRR) for diseases. RESULTS: The SRR for cardiovascular diseases was > 1 (P < 0.05). The SRR for endometrial cancer and ovarian cancer were < 1 (P < 0.05). CONCLUSION: COC may increase the risk of cardiovascular diseases and may protect from endometrial and ovarian cancer.

Adult↗

PubMed1996

[Combined surgical-orthodontic correction for mandibular protrusion].

Through the analysis of the treatment plans and the results of 159 patients with mandibular prognathism, the authors emphasized that orthodontic treatment plays an important role in the combined procedure in which the aims of orthodontic treatment include eliminating dental compensation, aligning the teeth, harmonizing arch compatibility, adjusting and maintaining occlusal relationship. The choice of surgical procedure used for setting back the mandible is closely related to the result of pre-operative orthodontic treatment. The body step osteotomy and vertical ramus osteotomy are the most commonly used procedure to set back the mandible after pre-operative orthodontic preparation.

Humans↗