Specificity of meal pattern analysis as an animal model of determining temporomandibular joint inflammation/pain.

Analyzing feeding behavior, and in particular meal duration, can be used as a biological marker for temporomandibular joint (TMJ) inflammation/pain. The present study determined the specificity of meal duration as a measure of TMJ inflammation/pain in a rodent model. The model was also used to test the efficacy of dexamethasone (DEX) as a treatment for TMJ inflammation/pain that was induced by TMJ injection of complete Freund's adjuvant (CFA). In the first study, anesthetized male Sprague-Dawley rats housed in computerized feeding modules received bilateral intra-articular knee injections of CFA or saline. The next day, CFA-injected rats had significant knee swelling and impaired mobility. Food intake in the CFA-injected group was reduced over the next two days and this was due to reduced meal number with no change in meal size. Notably, meal duration was normal in both the CFA and saline knee-injected groups. In the second study, male rats were assigned to one of four groups: Group 1, no CFA and no DEX treatment; Group 2, no CFA and treatment with DEX (0.4 mg/kg i.m. once daily); Group 3, bilateral TMJ CFA injection and no DEX treatment; and Group 4, bilateral TMJ CFA injection and treatment with DEX. CFA significantly increased TMJ swelling and stress-induced chromodacryorrhea in Group 3, but treatment with DEX attenuated these effects in Group 4. Compared to the controls, meal duration was significantly lengthened 24 and 48 h post-CFA injection in Group 3, whereas DEX treatment attenuated TMJ swelling, chromodacryorrhea and normalized meal duration. The data demonstrate that meal pattern analysis, and in particular meal duration, can be used as a non-invasive specific measure of TMJ inflammation/pain and can be used as a marker of DEX treatment efficacy.

Changes in placental atrial natriuretic peptide receptors associated with severe toxemia of pregnancy.

We have previously demonstrated the presence of atrial natriuretic peptide (ANP) specific receptors in normal human placentas. Since toxemia of pregnancy may affect important metabolic, transport and hemodynamic functions of placentas, we have asked the question whether binding properties of human placental ANP receptors are changed in patients with severe toxemia of pregnancy when compared to normal patients. ANP receptors in plasma membranes from normal and severely toxemic patients were characterized by in vitro radioligand assays utilizing [125I]-alpha-hANP. In all cases, we identified specific, high affinity, low capacity ANP binding sites in a microsomal fraction of human placentas. Although the total concentration of receptors did not differ between the two groups, the dissociation constant, KD, was significantly higher in placentas from severely toxemic patients than from normal controls. From the above we conclude that placental ANP receptors are dynamically modulated and their characteristics may be altered in severe toxemia of pregnancy.

Atrial natriuretic peptide receptors in sheep cotyledons.

Effects dependent on atrial natriuretic peptide are mediated through specific atrial natriuretic peptide plasma membrane receptors. We previously demonstrated the presence of specific atrial natriuretic peptide receptors in human placental membranes. We asked whether atrial natriuretic peptide specific receptors are present in sheep cotyledons. Sheep cotyledons were obtained from pregnant ewes at 125 to 142 days' gestation. Each cotyledon was separated into two components, the outer layer (maternal capsule) and the spongy inner layer (fetal component). A microsomal plasma membrane fraction was prepared from each layer. Atrial natriuretic peptide receptors were detected by in vitro radioligand techniques with 125I-alpha-human atrial natriuretic peptide. In sheep cotyledons there are two sets of atrial natriuretic peptide receptors that show either high-affinity/low-capacity or low-affinity/high-capacity binding characteristics. Moreover, membranes from the inner layer (fetal component) appear to have a lower concentration of high-affinity atrial natriuretic peptide binding sites than those from the maternal capsule.

Atrial natriuretic peptide receptors in guinea pig placentas.

The multiple physiologic effects of atrial natriuretic peptide are mediated through specific atrial natriuretic peptide plasma membrane receptors. We have attempted to determine whether atrial natriuretic peptide receptors are present in guinea pig placentas and subplacentas at approximately 45 and 65 days' gestation. A microsomal plasma fraction was prepared from each component. Atrial natriuretic peptide receptors were detected by in vitro radioligand techniques with alpha-human atrial natriuretic peptide labeled with iodine 125. In placentas we identified one set of specific binding sites for atrial natriuretic peptide at both gestational ages. Although the maximal concentration of the receptors did not change with advancing gestation, the dissociation constant was higher at 65 than at 45 days' gestation. In subplacentas two sets of binding sites were identified, one of low capacity-high affinity and the other of low affinity-high capacity. The maximal concentration of the atrial natriuretic peptide receptors did not change as a function of gestation. However, the dissociation constant, for both the high- and low-affinity sites, significantly decreased with advancing gestation.

Pregnancy-induced changes in the interaction of guinea pig myometrial beta-adrenergic receptors with l-isoproterenol.

The ability of myometrial beta-adrenergic receptors to form a "'high-affinity state" with beta-adrenergic receptor agonists might be greater in pregnant guinea pigs at greater than or equal to 0.9 of gestation than in nonpregnant animals. To determine whether this difference is due to pregnancy in general or is associated only with late pregnancy and to determine whether it persists in the postpartum period, we studied the interaction of l-isoproterenol with beta-adrenergic receptors in myometrial membranes obtained from nonpregnant (nulligravid) animals, pregnant (primigravid) animals at 0.3, 0.7, and 0.9 to 1.0 of gestation (term 65 days), and postpartum guinea pigs (2 to 3 days). The affinity of myometrial beta-adrenergic receptors for l-isoproterenol was measured by percent inhibition of -[125I]cyanopindolol binding. In the presence of magnesium chloride, the competition curves could be resolved into two affinity state of the beta-adrenergic receptor, "high" and "low," respectively, in all groups. The ratio of the dissociation constant of the "low"-affinity state to that of the "high"-affinity state was significantly higher in pregnant guinea pigs at greater than or equal to 0.9 of gestation than in nonpregnant or postpartum animals and in pregnant animals of earlier gestations. In the presence of guanosine triphosphate only one (low-affinity) state of the receptor was detectable. Thus it is only in pregnant guinea pigs at greater than or equal to 0.9 of gestation that the ability of myometrial beta-adrenergic receptors to form a high-affinity state is enhanced.

Atrial natriuretic peptide receptors in normal human placentas.

We studied whether plasma membranes from normal human placentas contain receptors for atrial natriuretic peptide. We identified specific, high-affinity, low-capacity atrial natriuretic peptide binding sites in the nonbrush border, microsomal fraction presumed to originate from cellular membranes near the fetal circulation. In contrast, no atrial natriuretic peptide binding sites could be identified in the brush border; the latter is exposed to maternal blood in the intervillous space. The presence of atrial natriuretic peptide binding sites in human placentas suggests that atrial natriuretic peptide may be involved in fluid and electrolyte homeostasis in human gestation.

Up-regulation of guinea pig myometrial beta-adrenergic receptors by intrauterine estradiol and progesterone pellets.

The effect of intrauterine implantation of 17 beta-estradiol and progesterone on the concentration and affinity of myometrial beta-adrenergic receptor were studied in nonpregnant, previously oophorectomized guinea pigs receiving intrauterine implants of either 17 beta-estradiol, progesterone, a combination of the two hormones, or placebo for 7 days. Myometrial beta-adrenergic receptors were characterized by use of (-)-iodine 125-cyanopindolol as the specific beta-adrenergic receptor ligand. On comparison with the control group, administration of 17 beta-estradiol or progesterone resulted in a severalfold increase in the concentration (Bmax) of myometrial beta-adrenergic receptor and a lesser but significant increase in the dissociation constant, KD. Although a combination of 17 beta-estradiol and progesterone treatment increased the concentration and the dissociation constant of beta-adrenergic receptors, it did not result in any synergistic or additive effect. We conclude that intrauterine administration of these sex steroid hormones, directly or indirectly, modulates myometrial beta-adrenergic receptor concentrations and affinity.

Treatment of oophorectomized guinea pigs with intrauterine 17 beta-estradiol pellets may modulate myometrial beta-adrenergic receptor binding properties.

Intrauterine 17 beta-estradiol pellets can induce an up-regulation of guinea pig myometrial beta-adrenergic receptor density and l-isoproterenol-dependent adenylate cyclase activity. Does 17 beta-estradiol influence the ability of beta-adrenergic receptors to form a "high affinity" state with l-isoproterenol, which is a necessary step for adenylate cyclase activation? Nonpregnant, oophorectomized guinea pigs received intrauterine pellets of either placebo, 17 beta-estradiol, progesterone, or 17 beta-estradiol plus progesterone for 1 week. 17 beta-Estradiol resulted in pharmacologic, whereas progesterone resulted in physiologic plasma 17 beta-estradiol and progesterone concentrations, respectively. The affinity of myometrial beta-adrenergic receptors for l-isoproterenol was measured by percentage of inhibition of -[125I]cyanopindolol binding. In all groups, the competition curves in the presence of magnesium chloride could be resolved into two affinity states of the beta-adrenergic receptor, "high" and "low," respectively. The ratio of their dissociation constants was not influenced by hormonal treatment. However, the relative concentration of beta-adrenergic receptors in the high affinity state was significantly higher in the 17 beta-estradiol-treated group than that in the control group. This correlates with the up-regulation in myometrial adenylate cyclase activity and suggests that myometrial beta-adrenergic receptor-adenylate cyclase function may be modulated by 17 beta-estradiol.

Radiologic abnormalities and autonomic neuropathology in the digestive tract of the ketonuric diabetic Chinese hamster.

Barium x-ray patterns of ketonuric diabetic Chinese hamsters displayed marked dilatation of the stomach, small and large intestine. Hypomotility was manifested by flocculation of barium in the small and large bowel. Impaired transit time was further characterized by prolonged emptying of the stomach (mean 570 min diabetics; 200 min controls) and delayed stool formation (mean 230 min diabetics; and 100 min controls) and passage (mean 457 min diabetics; 210 min controls). Ultrastructural analysis of Auerbach's myenteric plexuses of the small intestine indicated acute degeneration in certain distal, unmyelinated axons. Swelling, deposition of glycogen, aggregation of neurofilaments and dense accumulation of lamellar bodies were observed. The severity and frequency of barium flocculation, glycogen deposition, aggregation of neurofilaments and lamellar inclusion bodies in axons were directly related to duration of ketonuria. The data strongly suggest that autonomic neuropathology in the plexuses of Auerbach may be a critical factor underlying gastrointestinal dysfunction in the ketonuric diabetic Chinese hamster.