Comparative effects of nifedipine, verapamil, and diltiazem on experimental pulmonary hypertension.

The role of calcium-channel blocking agents in the treatment of pulmonary hypertension is not well defined. Consequently, the effects of diltiazem, nifedipine, and verapamil were compared in 3 groups of anesthetized dogs (n = 6 for each group). In each group, normoxic hemodynamic variables were recorded before and after increasing doses of diltiazem, nifedipine, and verapamil (5 X 10(-8) M/kg, low; 10(-7) M/kg, medium; and 10(-6) M/kg, high dose; given intravenously over 2 minutes). In addition, the effect of these doses on the pulmonary pressor responses to hypoxia (fractional inspired oxygen concentration [FIO2] 12%) and prostaglandin F2 alpha (PGF2 alpha) (5 micrograms/kg/min, intravenously for 4 minutes) was measured. During normoxia, high-dose nifedipine and verapamil decreased mean aortic pressure and systemic vascular resistance while increasing cardiac output in all dogs in both groups (p less than 0.01). Pulmonary vascular resistance, however, remained unchanged. High-dose diltiazem did not significantly alter cardiac output or pulmonary vascular resistance. During acute hypoxic pulmonary hypertension, verapamil decreased cardiac output by 30% (p less than 0.01) without appreciably altering pulmonary arterial pressure; thus pulmonary vascular resistance increased slightly (4.9 +/- 0.6 to 6.4 +/- 1.0 mm Hg/liter/min, difference not significant [NS]). Nifedipine decreased hypoxic pulmonary vascular resistance to normoxic values (p less than 0.01). Cardiac output increased 71% while pulmonary arterial pressure remained unchanged. Diltiazem administration produced no change in hypoxic pulmonary hemodynamic variables. The responses to diltiazem, nifedipine, and verapamil during acute pulmonary vasoconstriction induced by PGF2 alpha were similar to those induced by hypoxia. After verapamil, pulmonary vascular resistance tended to increase (7.3 +/- 1.3 to 8.1 +/- 1.4 mm Hg/liter/min, NS). Nifedipine, however, completely blocked pulmonary vasoconstriction by decreasing pulmonary vascular resistance to pre-PGF2 alpha levels (p less than 0.01). This was accompanied by a 157% increase in cardiac output and only a small increase in pulmonary arterial pressure (7 mm Hg). Again, diltiazem produced no change in pulmonary hemodynamic variables. In these acute studies, nifedipine appeared to be a more effective pulmonary vasodilator than verapamil or diltiazem.

Vasoactive intestinal polypeptide stimulates nonovarian progesterone secretion in rabbits.

Recent experiments conducted in this laboratory have shown that intravenous infusions of vasoactive intestinal polypeptide (VIP) induced significant increases in plasma progesterone (P) in female rabbits. The purpose of this study was to determine the organ source of this P and to clarify the mechanisms by which it is induced. Intravenous infusions of VIP (37.5, 75, and 150 pmol/kg per min for 60 min) produced acute dose-dependent increases in plasma P in intact estrous rabbits. In ovariectomized (OVX) animals, VIP infusion (75 pmol/kg per min) produced a P increase of the same magnitude. In animals both OVX and adrenalectomized (ADX), this VIP effect was eliminated. The only significant change noted in luteotropic hormone (LH) or follicle stimulating hormone (FSH) was a decrease in FSH immediately following VIP infusion (150 pmol/kg). VIP infusion significantly increased plasma cortisol in intact and OVX animals, but not in OVX/ADX animals. It is concluded that VIP primarily stimulates the adrenal component of P secretion in the rabbit, via mechanisms independent of LH or FSH.

Gender differences in facial reactions to facial expressions.

This study explored whether males and females differ in facial muscle reactivity when exposed to facial expressions. The study also examined whether the sex of the stimulus faces differentially influences the response patterns to facial stimuli. Thus, the sex was manipulated in a 2 x 2 factorial design by exposing males and females to slides of angry and happy faces displayed by both sexes. Facial electromyographic (EMG) activity was measured from the corrugator and zygomatic muscle regions. The subjects were also required to rate the stimuli on different dimensions. The results showed that angry faces evoked increased corrugator activity whereas happy faces evoked increased zygomatic activity. As predicted, these effects were more pronounced for females, particularly for the response to happy faces. Interestingly, there were no facial EMG effects for gender of stimulus. It was further found that males and females perceived the stimuli similarly. The results are consistent with previous findings indicating that females are more facially reactive than are males.

Evidence for Alfvén waves in solar x-ray jets.

Coronal magnetic fields are dynamic, and field lines may misalign, reassemble, and release energy by means of magnetic reconnection. Giant releases may generate solar flares and coronal mass ejections and, on a smaller scale, produce x-ray jets. Hinode observations of polar coronal holes reveal that x-ray jets have two distinct velocities: one near the Alfvén speed ( approximately 800 kilometers per second) and another near the sound speed (200 kilometers per second). Many more jets were seen than have been reported previously; we detected an average of 10 events per hour up to these speeds, whereas previous observations documented only a handful per day with lower average speeds of 200 kilometers per second. The x-ray jets are about 2 x 10(3) to 2 x 10(4) kilometers wide and 1 x 10(5) kilometers long and last from 100 to 2500 seconds. The large number of events, coupled with the high velocities of the apparent outflows, indicates that the jets may contribute to the high-speed solar wind.

Changes in bite force and chewing efficiency after denture treatment in edentulous patients with denture adaptation difficulties.

Masticatory function was studied by means of a chewing efficiency test and bite forces measurements in forty-nine edentulous patients who had applied for treatment with fixed protheses on osseointegrated dental implants. Registrations were performed with the original complete dentures and after treatment aiming at optimizing the dentures. The patients were divided into two groups and the post-treatment recordings were completed after adaptation periods of 2 and 6 months, respectively. The functional tests showed mainly small and non-significant changes after the denture treatment. Improvement was greater, however, in those with the poorest pre-treatment values. Chewing efficiency deteriorated after treatment in the older patients (more than 50 years) while it did not change in the younger ones. A longer adaptation period did not lead to better functional results. The findings are discussed in relation to the fact that the patients were waiting for implant treatment, with consequent psychological implications for interpretation.

Zymosan activation of plasma reduces hypoxic pulmonary vasoconstriction.

Small doses of endotoxin (15 micrograms/kg IV) inhibit the pulmonary vascular pressor response to alveolar hypoxia in the anesthetized dog. One of the actions of endotoxin is to initiate the alternate pathway of complement activation. Incubation of human plasma with zymosan (ZAP) will activate this pathway. We wished to see if ZAP would mimic the effect of endotoxin. Prior to ZAP, hypoxia (F1O2 12%) in 5 anesthetized dogs increased pulmonary vascular resistance (PVR: mm Hg/L/min) from 3.7 +/- 0.8 to 7.1 +/- 1.5. After 50 ml ZAP IV the PVR change with hypoxia was only from 3.6 +/- 0.6 to 3.9 +/- 0.8. Plasma heated to destroy complement prior to ZAP incubation in one experiment did not reduce the pressor response. In a further 5 dogs pretreated with meclofenamate (2 mg/kg IV) the PVR increased from 3.7 +/- 0.4 to 7.5 +/- 0.4 with hypoxia prior to IV ZAP and from 4.4 +/- 0.5 to 6.5 +/- 0.6 after ZAP. The effect of ZAP indicates that endotoxin may work through the activation of complement. The protection of the hypoxic pressor response by meclofenamate suggests that the ZAP inhibition (like endotoxin inhibition) may involve dilator prostaglandin-like substances.

Synthesis, characterization and inhibitory activities of (4-N3[3,5-3H]Phe10)PKI(6-22)amide and its precursors: photoaffinity labeling peptides for the active site of cyclic AMP-dependent protein kinase.

PKI(6-22)amide is a 17 residue peptide corresponding to the active portion of the heat-stable inhibitor of cAMP-dependent protein kinase. The peptide is a potent (Ki = 1.6 nM), competitive inhibitor of the enzyme. The photoreactive peptide analog (4-azidophenylalanine10)PKI(6-22)amide was synthesized in both its non-radiolabeled and tritiated forms by chemical modification of precursor peptides that were prepared by stepwise solid-phase synthesis. (4-Amino[3,5-3H]phenylalanine10)PKI(6-22)amide, the precursor for the radiolabeled arylazide peptide, was obtained by catalytic reduction of the corresponding peptide containing the 3,5-diiodo-4-aminophenylalanine residue at position 10. The purified PKI peptides were analyzed by HPLC, amino acid analysis, and u.v. spectra. In the dark, (4-azidophenylalanine10)PKI(6-22)amide inhibited the catalytic subunit of cAMP-dependent protein kinase with a Ki value of 2.8 nM. The photoreactivity of the arylazide peptide was demonstrated by time-dependent u.v. spectral changes on exposure to light. Photolysis of the catalytic subunit (4-azido[3,5-3H]phenylalanine10)PKI(6-22)amide complex resulted in specific covalent labeling of the enzyme. The data indicate that this peptide is a useful photoaffinity labeling reagent for the active site of the protein kinase.

Protein kinase inhibitor-(6-22)-amide peptide analogs with standard and nonstandard amino acid substitutions for phenylalanine 10. Inhibition of cAMP-dependent protein kinase.

The minimal structure in the heat-stable inhibitor protein of cAMP-dependent protein kinase required for a low nanomolar potency of inhibition is the peptide Thr6-Tyr-Ala-Asp-Phe-Ile-Ala-Ser-Gly-Arg-Thr-Gly-Arg-Arg-Asn-Ala-+ ++Ile22-NH2 (PKI-(6-22)-amide). While primary structural determinants for interaction with the protein kinase are distributed throughout the 17 residues of this peptide, we have previously shown that phenylalanine 10 in the NH2-terminal portion is a particularly important determinant for high affinity binding (Glass, D. B., Cheng, H.-C., Mende-Mueller, L., Reed, J., and Walsh, D. A. (1989) J. Biol. Chem. 264, 8802-8810). To investigate this requirement further, peptide analogs of PKI-(6-22)-amide in which various natural and nonstandard amino acids are substituted for phenylalanine 10 have been synthesized and tested for inhibitory potency against the catalytic subunit of the protein kinase. Consistent with the importance of the hydrophobicity of phenylalanine, an alanine 10 substitution analog exhibited a 270-fold decrease in inhibitory potency, whereas the leucine 10 analog lost only 33-fold in activity as compared to the parent peptide PKI-(6-22)-amide. Peptides containing the spatial conformation analogs D-phenylalanine, homophenylalanine, or phenylglycine were 60-120-fold less potent than the parent peptide. Peptides containing various para-substituted phenylalanines at position 10 were only 5-11-fold less potent. One exception to this was (4'-azidophenylalanine 10)PKI-(6-22)-amide, which was nearly equipotent with the parent inhibitor. The most potent analogs were those peptides containing highly aromatic residues at position 10. The 2'-thienylalanine 10, tryptophan (formyl) 10, tryptophan 10, and the 1'-naphthylalanine 10 analogs were 3-fold less potent, equipotent, slightly more potent, and 4-fold more potent than the parent peptide inhibitor, respectively. We conclude that phenylalanine 10 in PKI-(6-22)-amide, and presumably in the native protein inhibitor, interacts through specific hydrophobic and/or aromatic binding to a hydrophobic pocket or cleft near the active site of the protein kinase.

Diamide inhibits pulmonary vasoconstriction induced by hypoxia or prostaglandin F2 alpha.

Diamide oxidizes glutathione and other cellular sulfhydryl groups. It decreases calcium ATPase activity and alters mitochondrial calcium flux, probably as a result of the sulfhydryl oxidation. We examined the effect of diamide (5 mg/kg, iv) on pulmonary vascular reactivity in 12 anesthetized dogs. Diamide reversed the pulmonary vasoconstriction caused by hypoxia in seven dogs (control delta PVR + 2.5 +/- 0.6 mm Hg/liter/min; postdiamide delta PVR - 0.1 +/- 0.4 mm Hg/liter/min; P less than 0.01). The pulmonary pressor response to prostaglandin F2 alpha (5 micrograms/kg/min, iv) was also reduced (control delta PVR + 3.8 +/- 0.5 mm Hg/liter/min; postdiamide delta PVR + 1.1 +/- 0.7 mm Hg/liter/min; P less than 0.01). However, in a further five dogs, diamide had only a small effect on the pulmonary vasoconstriction caused by angiotensin II, while the pressor response to hypoxia was again inhibited. The mechanism by which diamide reverses pulmonary vasoconstriction is not certain but the effect is rapid, consistent, and reversible. Because the intravenous infusion of diamide does not produce systemic hypotension, during its period of action on the pulmonary vasculature, unlike the drugs currently available for the clinical treatment of pulmonary hypertension, further studies of its mechanism of action are indicated.

Effects of vasoactive intestinal polypeptide upon ovarian steroids, ovum transport and fertility in the rabbit.

The purpose of this study was to determine the effects of infused vasoactive intestinal polypeptide (VIP) upon reproductive function in the female rabbit. Intravenous infusions of VIP (37.5, 75, and 150 pmol/kg per min) induced acute dose-dependent increases in plasma progesterone (P) but not estradiol (E2) or testosterone (T) in estrous rabbits. This P effect was not associated with an increase in plasma prolactin (Prl) and was not altered by pretreatment with a Prl-inhibiting regimen of bromocriptine. In rabbits stimulated to ovulate with 75 IU human chorionic gonadotropin (hCG) and coitus, plasma P and E2 increased, reaching a peak at 180 min following stimulation. VIP (75 pmol/kg per min) infused from 120 to 180 min following the ovulatory stimuli increased this P peak but did not effect E2 levels. This VIP infusion had no effect upon fertility or upon the number of corpora lutea, uterine implants, or viable conceptuses. Infusions of VIP for 60 min at the P peak, and for 240 min at the time of ovulation, had no significant effect upon ovum pickup or the rate of ovum transport. These observations suggest that 1) VIP infusions in rabbits can increase plasma P from both the basal levels of estrus and from the peak levels preceding ovluation. 2) Infusions of VIP at the time of the preovulatory steroid surge or during ovulation have little effect upon fertility or gamete transport in the rabbit. 3) Endogenous VIP may play a role in the regulation of P secretion in the rabbit.

Health, Society, and the Physician: problem-based learning of the social sciences and humanities. Eight years of experience.

We describe a required course for fourth-year medical students focusing on the application of the social sciences and the humanities to critical decisions in the practice of medicine. During 160 hours (70 with faculty contact) in a 7-week period, active, patient-centered, problem-based learning takes place in small collaborating groups, is facilitated by trained tutors, and uses computerized access to library materials plus reference files and resource persons. Major issues identified in the cases are clarified in complementary lectures and symposia. Formative evaluation is ongoing within tutorial groups. Summative evaluation is determined by the individual student's performance in a final complex management problem using a simulated patient. Evaluation of the course, and the basis for its ongoing revision, are provided by participating students and faculty, whose evaluations of the course have been favorable in 80% to 90% of cases.