Quality Measurement and Improvement Study of Surgical Coronary Revascularization: Medication Adherence (MISSION-2)

Background

Secondary preventive therapies play a key role in the prevention of adverse outcomes after coronary artery bypass grafting (CABG). However, medication adherence after CABG is often poor, and conventional interventions for improving adherence have limited success. With increasing penetration of smartphones, health-related smartphone applications might provide an opportunity to improve adherence. Carefully designed trials are needed to provide reliable evidence for the use of these applications in patients after CABG.

Methods

The Measurement and Improvement Studies of Surgical Coronary Revascularization: Medication Adherence (MISSION-2) study is a multicenter randomized controlled trial, aiming to randomize 1000 CABG patients to the intervention or control groups in a 1:1 ratio. We developed the multifaceted, patient-centered, smartphone-based Heart Health Application to encourage medication adherence in the intervention group through a health self-management program initiated during hospital admission for CABG. The application integrated daily scheduled reminders to take the discharge medications, cardiac educational materials, a dynamic dashboard to review cardiovascular risk factors and secondary prevention targets, and weekly questionnaires with interactive feedback. The primary outcome was secondary preventive medication adherence measured by the Chinese version of the 8-item Morisky Medication Adherence Scale at 6 months after randomization. Secondary outcomes included all-cause death, cardiovascular rehospitalization, and a composite of death, myocardial infarction, stroke, and repeat revascularization.

Discussion

Findings will not only provide evidence regarding the feasibility and effectiveness of the described intervention for improving adherence to CABG secondary preventive therapies but also explore a model for outpatient health self-management that could be translated to various chronic diseases and widely disseminated across resource-limited settings.

Trial Registration

https://clinicaltrials.gov (NCT02432469).

Review Recent progress in identification and characterization of loci associated with sex-linked congenital cataract

Congenital cataract is a common cause of blindness in children; however, its pathogenesis remains unclear. Genetic factors have been shown to play an important role in the pathogenesis of congenital cataract. The current genetic models of congenital cataract include autosomal dominant, autosomal recessive, and sex-linked inheritance. Sex-linked congenital cataract could be inherited through the X or Y chromosome. Congenital cataract is a symptom associated with several X-linked disorders, including Nance-Horan syndrome, Lowe syndrome, Conradi-Hünermann-Happle syndrome, oculo-facio-cardio-dental syndrome, and Alport syndrome. On the other hand, the mechanism and characteristics of Y-linked congenital cataract remains to be identified. Despite its rarity, sex-linked congenital cataract has been known to seriously affect the quality of life of patients. In this review, we present our current understanding of the genes and loci associated with sex-linked congenital cataract. This could help identify novel approaches for the prevention, early diagnosis, and comprehensive disease treatment.

[Effect of hypoxia on activity of hypothalamo-pituitary- adrenal-cortex axis in rat]

AIM AND METHODS

In this experiment we used the methods of simulated hypoxia in a low-pressure cabin and RIA to investigate the effect of hypoxia on secretion of corticotropin-releasing factor (CRF) from hypothalamus and corticosterone from adrenal-cortex. And compare the effects of hypoxia on secretion of CRF and corticosterone in rat exposed to hypoxia for different time.

RESULTS

During acute hypoxia the secretion of CRF and level of plasma corticosterone rose significantly comparing with control. After 5 days of exposed to hypoxia the augment of secretion of CRF and level of plasma corticosterone decreased and to 15 days exposed to hypoxia the secretion of CRF and level of plasma corticosterone approached to control.

CONCLUSION

Hypoxia (2 h, 24 h) significantly activated HPA axis. After 5 days exposed to hypoxia the activity of HPA axis attenuated and began to recovery. After 15 days exposed to chronic hypoxia the activity of HPA axis has recovered to control level.

[The autonomic nervous system involved in regulation of immune function in rats during hypoxia]

AIM

To study of autonomic nervous system modulation of lymphocyte proliferation during hypoxia.

METHODS

Rats were exposed to 5 km and 7 km altitude in a hypobaric chamber for 24 h or 48 h, the effect of autonomic nervous system on mitogen-induced spleen lymphocyte response to the acute hypoxia was investigated.

RESULTS

When rats were exposed to 5 km altitude for 24 h, which inhibited spleen T lymphocyte proliferation induced by concanavalin (Con A), but the action was abolished through peripheral sympathetic-destroyed. When mouse were exposed anoxia environment at 0.07 MPa for 10 min, the norepinephrine and epinephrine in plasma were increased markedly. T cells of rats were in vitro incubated simultaneously with ACh showing a concentration dependent enhancement of T cell proliferation. The plasma levels of ACh were decreased after rats were exposed to 5 km for 24 h.

CONCLUSION

Autonomic nervous system was involved in the regulation of immune function in rats during hypoxia.

[The radioimmunoassay of growth hormone and prolactin and its application]

AIM

To set up a highly specific and sensitive double antibody radioimmunoassay (RIA) for determining the contents of growth hormone (GH) and prolactin (PRL) in pituitary and plasma of rats; To study the effects of acute hypoxia on GH and PRL of rats.

METHODS

We use chloramine-T technique iodinate antigen and choose the equilibration and saturated procedure of RIA to add the preparations.

RESULTS

Exposed to 7 km-hypoxia for 0.5 h, pituitary GH content increased (P < 0.05) and conversely, plasma GH levels were suppressed (P < 0.05); while the PRL levels in both pituitary and plasma were suppressed (P < 0.01); and there was no significantly difference between 5 km hypoxia groups and control.

CONCLUSION

We have successfully established the method of radiolabel and double antibody RIA with highly sensitivity; acute hypoxia (7 km) suppressed the secretion of GH and PRL in rats.

Effects of angiotensin II on release of CRH and AVP from hypothalamus during acute hypoxia

AIM

To investigate the effects of angiotensin II (Ang II) on corticotropin-releasing hormone (CRH) and argipressin (AVP) release from median eminence (ME) of hypothalamus during acute hypoxia in rats.

METHODS

Simulated hypoxia was performed in a hypobaric chamber. CRH and AVP were determined by radioimmunoassay (RIA). Plasma corticosterone concentration was measured by fluorometry.

RESULTS

Ang II did not influence CRH release induced by hypoxia [CRH in group pretreated with Ang II (16 +/- 8) ng/ME vs control (15 +/- 4) ng/ME, both exposed to hypoxia with simulated altitude 7 km (8.2% O2)]. Ang II enhanced AVP release, from (5.7 +/- 1.6) ng/ME in control decreasing to (2.6 +/- 1.2) ng/ME (P < 0.05), meanwhile plasma corticosterone concentration was also increased markedly, from (356 +/- 58) in control to (536 +/- 134) micrograms/L plasma (P < 0.05), which was partly abolished by administration of AVP antiserum.

CONCLUSION

Ang II might stimulate hypothalamo-pituitary-adrenal axis (HPA) through activating AVP but not CRH release during acute hypoxia.

Hypoxia influences enkephalin release in rats

To investigate hypoxia effects on leucine-enkephalin (L-ENK) levels of median eminence (ME) of hypothalamus in rats, and the possible glucocorticoid involvement in modulation. Hypoxia was stimulated in a hypobaric chamber. L-ENK levels were measured by specific radioimmunoassay during acute, and a comparison of L-ENK alteration was taken for bilateral adrenalectomy (ADX) with or without a replacement of dexamethasone (DEX). Acute hypoxia 10.8% O2 for 30 min and 2 h markedly enhanced L-ENK levels of ME from 23.99+/-7.25 in control to 51.26+/-16.96 (P<0.01) and 53.29+/-26.10 ng/mg protein (p<0.01), and acute hypoxia at 8.2% O2 significantly increased L-ENK of ME to 36.76+/-15.25 (p<0.05) and 32.09+/-3.58 ng/mg protein (p<0.05). The increased L-ENK was returned to normoxic level when hypoxia (10.8% O2) exposure lasted for 24 h. After ADX, 10.8% O2 hypoxia induced a sharp decline of L-ENK in the ME, but this decline was completely reversed by treatment with DEX (500 microg/rat, i.p.). Acute hypoxia increases L-ENK level of hypothalamic ME in rats, which may present a reduced and/or inhibited release of L-ENK, acting through a fast negative feedback mechanism of acute hypoxia activated high circulating glucocorticoid level.

Hypoxia influences somatostatin release in rats

The impact of hypoxia on somatostatin (SS) secretion from the median eminence (ME) of the hypothalamus and the possible glucocorticosteroid involvement in modulating secretion, were investigated in adult male rats exposed to hypoxia. SS levels were measured by specific radioimmunoassay during acute and prolonged hypoxia as well as after bilateral adrenalectomy (ADX) with or without a replacement with dexamethasone (DEX). The results were as follows: (a) acute hypoxia (5 km altitude, 10.8% O(2)) for 2 and 24 h markedly increased SS content in ME, but acute severe hypoxia (7 km, 8.2% O(2) for 24 h) markedly decreased SS level in ME. (b) Chronic hypoxia (10.8% O(2)) from 5 to 25 days exposure did not significantly affect SS content of ME. (c) ADX alone increased SS content of ME and this increase was further enhanced after 2 h exposure to hypoxia. (d) The increased SS in ME of ADX rats was blocked by replacement with DEX (500 microg/rat i.p.). The data presented suggest that acute hypoxia stress may increase or decrease SS content of ME in rats, depending on the severity and duration of the hypoxia and that the stimulatory action of hypoxia on SS content of ME be may in part mediated by the increased corticosterone levels during hypoxia.

The response of growth hormone and prolactin of rats to hypoxia

Effects of acute and chronic hypoxia on growth hormone (GH) and prolactin (PRL) of male rats were studied in a simulated hypobaric chambers at altitudes of 5 km (10.8% O2) and 7 km (7.2% O2), respectively. Acute hypoxia caused decreased plasma GH and increased pituitary GH content; both pituitary and plasma PRL contents at 2 h were decreased and plasma PRL level increased at 24 h. Prolonged exposure of hypoxia (5 km) to 25 days, both pituitary and plasma GH were obviously lower than control and pituitary PRL levels were decreased but plasma PRL increased markedly. The data presented suggest that long-term of hypoxia (10.8% O2) significantly suppresses body growth of rats and inhibits GH release and/or biosynthesis, which may in part correlate with decreased body weight gain; high circulating PRL concentration may be of significance in physiological adaptation to chronic hypoxia.

[The enhancing effects of arginine-vasopressin on antibody level and lymphocyte proliferation of rats]

The effects of arginine-vasopressin (AVP) on some immune parameters of rats were studied by using icv of AVP. The hemolysin to sheep red blood cell and IgG production were enhanced by icv of 100, 800 ng AVP. Both the actions were partly blocked by icv preinjection of the V1 receptor antagonist DPAVP. It was also found that the NE and corticosterone levels in the serum of rats were significantly reduced after icv of AVP. The above results suggest that AVP executes immunofunctions through V1 receptors in the paraventricular nucleus of the brain. Considering our previous results, the AVP enhanced immunofunction may be related to its inhibition of corticotropin releasing factor release or the excitatory activity of sympathetic nerves.

[Beta-endorphin involved in the regulation of humoral immune function of rats during acute hypoxia]

In order to investigate the role of beta-endorphin in the regulation of humoral immune function of rats during acute hypoxia, the effects of beta-endorphin on mitogen-induced spleen lymphocyte DNA synthesis and hemolysin formation as well as IgG production to chicken egg albumen were observed. It was found that after rats received icv injection of beta-endorphin (1 ng/rat), the T-lymphocyte DNA content, the hemolysin-forming capacity of SRBC-sensitized rats and the IgG level were reduced significantly compared with the control (icv normal saline). Similar suppressive effects on immune function could be found after rats were exposed to 7 km altitude in a hypobaric chamber for 48 h. Pretreatment with icv injection of naltrexone, the immunosuppressive effects of acute hypoxia were partially blocked. Icv administration of beta-endorphin produced an increase in splenic cathcholamines, similar to those of hypoxia treated group (7 km for 12 h). All the above findings suggest that beta-endorphin may modulate the immune response to hypoxia stress via opioid receptor and its inhibitory action may be mediated by activating sympathetic nervous system.

[Norepinephrine regulation of T-lymphocyte proliferation of rat during acute hypoxia]

Interaction between the immune and neuroendocrine systems has long been noted. In the present study, the role of norepinephrine (NE) in immunoregulation of rats during simulated hypoxia in hypobaric chamber was examined. It was found that 7 km for 24 h of hypoxia inhibited T-lymphocyte proliferation by 41%. 7 d and 20 d of hypoxia, simulating 5 km altitude, reduces T-lymphocyte proliferation respectively 34% and 60%. Intracerebroventricular (i.c.v.) injection of 5 x 10(-6) mol/L NE decreased T-lymphocyte proliferation by 29%. I.c.v. injection of phentolamine 25 micrograms/rat prior to 7 km for 10 h hypoxia attenuated the hypoxia-induced suppression of T-lymphocyte proliferation from 42% to 21%. In additon, 7 km 10 h hypoxia increased CRF levels in blood and catecholamines in hypothalamus. An increased circulation CRF level was also noted after NE injection (i.c.v.) of 5 x 10(-6) mol/L. Hypoxia corresponding 7 km altitude for 10 h stimulates spleen-lymphocytes incubated with CRF, but T-lymphocyte proliferation decreclsed with increasing CRF concentration. These findings suggest that hypoxia inhibits T-lymphocyte proliferation probably through an immune inhibition action by CRF-NE.

Energy expenditure and quantitative oxidation of nutrients in rats (Rattus norvegicus) kept in different thermal environments and given two levels of dietary fiber

A study was performed to investigate the effect of environmental temperature (16 degrees C, 24 degrees C or 32 degrees C) and dietary fiber (DF) on energy expenditure and quantitative oxidation of nutrients in rats. Forty-eight male rats, initial body weight 90-105 g, were allocated to eight groups in two series. The rats kept at 24 degrees C was repeated in both series. Low and high fiber diets (56 vs. 257 g DF/kg dry matter) were studied in 6-week balance experiments. The rats in all groups were offered the same amount of air-dried food. Indirect calorimetry was used to measure the energy metabolism. The difference in heat production (HP) calculated by RQ and CN methods was < 2% and was not affected by environmental temperature and DF. The relation between fat and protein oxidation changed from 1.54 to 1.00 when the ambient temperature changed from 16 degrees C to 32 degrees C. The contribution of carbohydrate oxidation to total HP was lowest at 16 degrees C, whereas the fat and protein oxidation was highest at 16 degrees C. The oxidation of nutrients was not influenced by DF. The additional energy retained at the higher temperatures had a constant ratio between fat and protein, i.e., 70:30. At an energy retention of 65.8 kJ/kg0.75 d or less, body fat is mobilized and only protein deposited. Because of higher HP, rats living in the cold environment used more fat as substrate for HP than rats kept in warmer environments. The cold environment results in an increase in the amount of interscapular brown adipose tissue, but no significant difference was found between DF levels.

[Inhibition effect of hypoxia on humoral immunity of rats]

To study the effect of hypoxia on humoral immunity function of rat and Ochotona curzoniae (pika), the specific antibody production to novel antigen IgG and immunoresponse to sheep red blood cell (hemolysin forming) were measured. The results show that hypoxia at altitude of 5 km and 7 km for 10 d resulted respectively in 10.3% (P < 0.05) and 21.9% (P < 0.05) decrement in hemolysin formation in rats, as compared with the control group kept at 2.3 km. When the rats were secondarily immunized and kept at the same hypoxia for 10 d, the reduction in hemolysin formation was 4.2% (P < 0.05) and 4.6% (P < 0.05) for the two respective altitudes. These changes, however, were not found in pikas. When rats were immunized two days before hypoxia, 5 km hypoxia for 5 d and 8 d failed to suppress hemolysin formation. Intracerebroventricular (i.c.v.) injection of CRF (1.0 microgram/rat), decreased hemolysin formation and production of IgG by 8.6% (P < 0.05) and 14.0% (P < 0.05) respectively, but intraperitoneal (i.p.) injection of CRF (1.0 microgram/rat) had no effect. On the other hand, i.c.v. injection of CRF receptor antagonist (alpha-helical CRF (9-41), 50 micrograms/rat) prior to 7 km hypoxia caused a hypoxia-induced suppression of IgG production from 24.2% to 12.1% (P < 0.05). Adrenalectomy in rats lowered hemolysin formation by 6.6% (P < 0.05). The above results demonstrate that hypoxia suppresses humoral immunity function and alters initial antigen processing probably through an increase of CRF in the central nervous system.

Hypoxia effects on hypothalamic corticotropin-releasing hormone and anterior pituitary cAMP

AIM

To study the effects of acute and chronic hypoxia on hypothalamus-anterior pituitary-adrenocortex axis.

METHODS

Rats and pikas were exposed to different altitude and periods. Animals were injected with CRH, Arg and NE in the third ventricle of the brain of rats.

RESULTS

Anterior pituitary cAMP and plasma corticosterone levels of rats obviously increased during 1 h of hypoxia. cAMP was increased from 2.23 +/- 0.13 of control group to 7.7 +/- 0.7 of 5 km and 13.4 +/- 1.9 nmol/g wet tissue of 8 km, respectively. i.c.v. CRH, Arg and NE all activated HPA axis. The effects of CRH were most potent. CRH 2 microL 0.75 nmol i.c.v increased anterior pituitary of cAMP from 3.5 +/- 0.4 of control to 22.4 +/- 2.2 nmol/kg wet tissue. Stimulating altitude of 5000 m resulted in a 16.9% decrease in corticosterone level (P < 0.05), 8000 m resulted in a 47.5% decrease (P < 0.01) after hypoxia for 25 d. Hypoxia did not activate HPA axis in pikas.

CONCLUSION

1) Hypoxia stress activates the secretion of corticotrophin (ACTH) via cAMP; 2) Adrenocotical function of rats decays during chronic hypoxia; 3) Arg and NE regulate the secretion of plasma corticosterone and synthesis of pituitary cAMP at the hypothalamus level; 4) Hypoxia tolerance of the pika was high.

[Effect of argipressin and its related compounds on corticotropin releasing hormone contents in hypothalamus of rats]

The paper mainly stresses on the effect of argipressin (Arg), 2-destyrosyl-3-desphenyl-alanyl-9-desglycyl-amide-Arg (Arg4-8), [1-deaminopenicillamine, 2-(o-methyl)tyrosine]-Arg (DPArg) and Arg antiserum on corticotropin releasing hormone (CRH) contents in median eminence (ME) and the level of plasma corticosterone after injected into the third ventricle of rats. The results show: 1) the CRH contents in ME significantly reduced with icv 100, 200, and 800 ng of Arg; 2) 100 ng of Arg4-8 and Arg antiserum (2 microliters, 1:1 diluted with 0.9% saline) increased CRH contents in ME and enhanced plasma corticosterone; 3) DPArg had no effect on CRH level but blocked the inhibitory role of Arg on central CRH. These results suggest that Arg acts as an inhibitory factor in regulating central CRH level and V1 receptor is involved.

Reset of feedback in the adrenocortical system: an apparent shift in sensitivity of adrenocorticotropin to inhibition by corticosterone between morning and evening

There is evidence in man and rats that higher circulating levels of glucocorticoids are required to normalize basal unstimulated ACTH levels at the peak of the circadian rhythm than at the trough. To explore this phenomenon, we tested the inhibitory effect of constant levels of corticosterone on plasma ACTH in the morning (AM) and evening (PM) in young male rats implanted with fused pellets of corticosterone-cholesterol at the time of adrenalectomy (ADX+B) and studied 5 days later. There was a marked shift of the plasma corticosterone-ACTH inhibition curve to the right between AM and PM, demonstrating that the efficacy of corticosterone feedback inhibition of ACTH is less in the PM. Comparison of plasma ACTH and corticosterone levels during 24 h in sham-adrenalectomized rats (SHAM-ADX), adrenalectomized rats (ADX), and ADX+B revealed constantly low ACTH in SHAM-ADX, constantly high ACTH in ADX, and biphasic ACTH levels in ADX+B. Corticosterone levels were biphasic in SHAM-ADX and were constant in the other two groups. These results again showed a shift in corticosterone feedback efficacy as a function of the time of day and also suggested that basal ACTH secretion is maintained in the low normal range in intact rats because of the marked diurnal rhythm in corticosterone. The sensitivity of the pituitary ACTH response to exogenous CRF did not change between AM and PM in either intact or ADX+B showing that the shift in feedback sensitivity to corticosterone does not reside in the pituitary. The response of the entire adrenocortical system to histamine stress was shown to be equivalent in both the AM and PM, suggesting that feedback sensitivity of the entire system to corticosterone does not change as a function of the time of day. We conclude from these results that there is an apparent diurnal change in ACTH sensitivity to corticosterone feedback that can be defined operationally as reset. We believe that the site of feedback being tested shifts solely from the pituitary in the AM (at the nadir of the rhythm) to the brain and the pituitary in the PM (at the peak of the rhythm). The lack of the normally high transients of corticosterone that occur in SHAM-ADX rats results in increased brain drive of the pituitary in ADX+B.

Exploratory behavior, learning ability, and thyroid hormonal responses to stress in female rats rehabilitating from postnatal hypothyroidism

Newborn female Long-Evans rats were divided into groups of normal, hypothyroid [0.1% propylthiouracil (PTU) a reversible antithyroid goitrogen in the litter's drinking water], and hypothyroid rehabilitated (PTU water from birth to day 25, normal water thereafter). The rats were tested for several adaptive behavioral tasks between 40 and 90 days of age. At day 50, serum concentration of TSH and thyroid hormones revealed no detectable amounts of T4 and a 10-fold increase in TSH in the hypothyroid rats. At the same age in the rehabilitated animals, TSH levels were still below normal, a deficit fully normalized by day 90. Normal 50-day-old rats responded to pain stress (electric footshocks) by a significant depression of serum T4 and elevation of T3 levels within 10 min of treatment, whereas the rehabilitated animals exhibited an opposite pattern of response, i.e., an increase in the circulating T4 and a decrease in T3. At 50 days of age, both hypothyroid and rehabilitated rats showed decreased exploratory activity and no habituation in the hole-board test, whereas the locomotor activity of the rehabilitated females was significantly higher than that of the normals. No differences were found in the scores of passive avoidance learning (one trial step-through) among the three groups. Similarly, the rate of acquisition of the active one-way conditioned avoidance response (CAR) of the hypothyroid and rehabilitated rats did not differ significantly from that of the controls. However, the hypothyroid rats required significantly more unconditioned stimuli (footshocks) to acquire CAR and showed longer response latency and less intertrial responses. Although the hypothyroid rats showed no extinction of CAR, the rehabilitated rats were capable of extinction to an extent indistinguishable from normal rats. But compared with the normal animals, the rehabilitated rats showed significantly higher intertrial activity during both the acquisition and extinction phases of CAR.

Effects of melatonin and control injections on pineal serotonin and norepinephrine: afternoon injections lower serotonin levels thirty-six percent at light-dark transition

Pineal weight and serotonin (5-HT) and norepinephrine (NE) contents were studied in male Sprague-Dawley rats that were maintained under controlled light:dark conditions (LD 14:10; lights on 0700-2100) and that received daily subcutaneous injections of either melatonin (20 micrograms in 0.1 ml per animal) or the same volume (0.1 ml) of vehicle alone, at one of two times (0800-0900 or 1800-1900). Animals were sacrificied at four times (1000, 1400, 2000, or 2300) on the day after the last of the 7 consecutive d of injection. Pineal glands were quickly weighed and then frozen for 5-HT and NE assay by the Maickel and Miller extraction and fluorescence methods. Pineal NE content showed differences related to time of day, in confirmation of early work. But no effects attributable specifically to melatonin were found. Melatonin also failed to affect pineal 5-HT content significantly. But injection of either melatonin or vehicle at 1800-1900 led to a reduction in 5-HT content averaging 36% when sampled at either 2000 or 2300, and in comparison with animals injected at 0800-0900. It is suggested that a stresslike or zeitgeberlike effect of injections within a critical period at the end of the daily light phase can cause an earlier-than-normal daily fall in pineal 5-HT content.

Active products of porcine trypsin after autolysis

Porcine trypsin obtained from pancreas residues subsequent to insulin removal undergoes autolysis when subjected to chromatography and gives rise to new forms of autolyzed products with intra-chain split at bonds Lys145-Ala146 and Arg105-Val106. Incubation of 1% solutions of porcine trypsin either at pH 5.0 or at pH 9.1 induces autolysis to give active products involving one or two specific cleavages of bonds Lys145-Ala146 and Arg105-Val106 or Lys131-Ser132, as well as inactive degraded products. No evidence has been obtained that on autolysis of porcine trypsin, and active fragment with molecular weight lower than that of the parent molecule was identified. The active forms of autolyzed products of porcine trypsin have almost the same specific activity as the intact enzyme when assayed against BAEE. They are of the same molecular weight as the parent molecule. These findings indicate that that active forms of autolyzed products maintain the specific three-dimensional structure essential for the catalytic activity of the trypsin molecule.