[Clinical experiences of granulocyte colony stimulating factor for granulocytopenia after AC bypass]

We have successfully treated 3 cases of granulocytopenia, using Granulocyte Colony Stimulating Factor (G-CSF) after AC bypass surgery. All cases were male, aged 68, 75 & 54 years old, and underwent AC bypass surgery without transfusion except in case 1. Granulocyte cell counts decreased to 135/mm3 on 39th post-operative days (POD) in case 1, 624/mm3 on 13 rd POD in case 2, and 514/mm3 on 20th POD in case 3. In case 1, 300 micrograms of G-CSF was given intravenously for 3 days. In case 2, 100 micrograms of G-CSF for 1 day and 50 micrograms for 3 days was given subcutaneously, and in case 3, 100 micrograms of G-CSF was also given subcutaneously for 2 days. And their granulocyte cell counts all increased within few days. G-CSF is effective for patients with granulocytopenia after AC bypass surgery, but we need more experiences to know the best way of administration.

Activation energy for permeation of phosphonium cations through phospholipid bilayer membrane

The conductance caused by translocation of various phosphonium cations across phospholipid (from soybean) bilayer membrane was measured. Phosphonium cations used were tetraphenylphosphonium (TPP+) and triphenylalkylphosphonium cations formulated as (Phe)3-P(+)-(CH2)nCH3 (n = 0-5). The conductance was dependent on voltage applied externally to the membrane in accordance with a theory developed by previous authors. Using the theory, values of beta K(i) were determined, where beta and k(i) are a linear partition coefficient and a rate constant of transmembrane ion transport, respectively. Since beta k(i) depended on the phosphonium ion concentration, values extrapolated to infinite dilution, (beta k(i))0, were determined. Temperature dependence of (beta k(i))0 allowed us to estimate the activation energy of transport, Ea. For TPP+ thermodynamic values obtained were consistent with values calculated by Flewelling and Hubbell [(1986) Biophys. J. 49, 541-552]. When (Phe)3-P(+)-(CH2)nCH3 (n = 0-5) were used, E(a) depended on the odd or even of n. This "odd and even" pattern was observed in a variety of phenomena such as solubility in water, equivalent ionic conductivity in water, and 31P NMR chemical shift.

Opposing effects of indomethacin and nordihydroguaiaretic acid on macrophage function and tumor growth

The effects of indomethacin (INDO) and nordihydroguaiaretic acid (NDGA) were compared on macrophage function and tumor growth. Intraperitoneal injections (5 mg/kg/day, 6, 8 or 9 days) of INDO in C57BL/6 mice stimulated the cytotoxicity of peritoneal macrophages and inhibited growth of subcutaneous B16 melanoma, whereas NDGA injections suppressed macrophage cytotoxicity, increased macrophage prostaglandin-E2 (PGE2) release, and enhanced the tumor growth. Further, pretreatment of macrophages in vitro with the INDO group serum increased cytostasis against B16 tumor cells, while the use of NDGA group serum reduced it. Incubation of tumor-bearer's macrophages in vitro with INDO (10(-6) M and 10(-7) M) or 10(-6) M NDGA for 4 h reduced PGE2 release, but 10(-7) M NDGA markedly enhanced the PGE2 release. Our data indicate that INDO and NDGA are able to modulate the macrophage function directly, and produce opposing effects on macrophage function and tumor growth. Inhibitory actions of INDO and NDGA on the cyclooxygenase or lipoxygenase pathway of arachidonic acid metabolism appear to contribute to their effects.

Cutaneous arterial fibromuscular dysplasia: a case report and electron-microscopic study

A case of a 39-year-old female with fibromuscular dysplasia (FMD) manifesting subcutaneous pulsatile nodules on the right side of her forehead and on her right wrist is reported here. These nodules proved to be FMD aneurysms of the frontal ramus of the right superficial temporal artery and the right radial artery. The patient had also suffered a stroke with subarachnoidal bleeding as a result of this disease. Angiographic examination showed aneurysms in the union and the bilateral vertebral arteries, a branch of the right renal artery, and one the right lumbar artery. A biopsy specimen taken from the frontal branch of the right superficial artery revealed segmental intimal thickening consistent with intimal fibroplasia type FMD upon histological examination. Electron-microscopic findings were also discussed in connection with the histogenesis of the disease. This appears to be the second case of FMD involving arteries in the skin to be reported in the dermatological literature.

Hydrocephalus due to villous hypertrophy of the choroid plexus in the lateral ventricles. Case report

A case is reported of hydrocephalus due to overproduction of cerebrospinal fluid (CSF) caused by villous hypertrophy of the choroid plexus in the lateral ventricles. A 7-year-old girl with mental retardation developed gait disturbance; hydrocephalus and a Dandy-Walker cyst were detected on computerized tomography. She was initially treated with a ventriculoperitoneal shunt; however, shunting failed to control the hydrocephalus. The excessive outflow of CSF suggested choroid plexus abnormality, and magnetic resonance (MR) imaging revealed enlargement of the choroid plexus in both lateral ventricles. The patient was therefore diagnosed as having hydrocephalus induced by overproduction of CSF, which was controlled by resection of the choroid plexus. Histological examination showed the structure typical of normal choroid plexus. This is a rare case of villous hypertrophy of the choroid plexus in which MR imaging assisted in the diagnosis.

Responses of contractile properties in rat soleus to high-energy phosphates and/or unloading

Responses of contractile properties of soleus to unloading and/or changes in high-energy phosphate contents were studied in rats. Reduction of high-energy phosphates, especially phosphocreatine, in ankle extensors was induced by feeding beta-guanidinopropionic acid (beta-GPA). The major finding in the study was that the fatigability and speed-related contractile properties responded to unloading and creatine supplementation in a similar manner. The high-energy phosphate contents tended to be elevated after 10-d supplementation of creatine and hindlimb suspension. The shift toward slow-type, mainly due to an increased one-half relaxation time, was seen in rats fed beta-GPA. Such a shift was reversed by feeding creatine or by hindlimb suspension; however, the suspension-induced shift of contractile properties toward fast-type was not prevented completely by beta-GPA feeding. Although the muscle fatigue resistance did not change by beta-GPA feeding alone, the decrease in fatigue resistance following suspension and creatine supply was less in the beta-GPA group. It is suggested that the levels of high-energy phosphates and tension production play important roles in the regulation of contractile properties of the soleus muscle.

Work stress and depressive symptoms among Japanese information systems managers

The aim of the present study is to investigate the task-specific work stressors of IS (Information Systems) managers and to analyze the effect of these work stressors on depressive symptoms among these managers. A questionnaire including 33 items on work stressor was designed. Three hundreds of samples were gathered. The response-rate was 66.4%. Factor analysis suggested that these 33 items were categorized into 8 factors; job-overload, project-management, mental-rewards, job-latitude, communication with users, career development, technical difficulty, and work-environment. Eight work stressor scores were constructed using this Factor analysis. Using the 8 stressor-scores, and 6 items of background data, multiple regression analysis was conducted on the depressive symptoms score. Depressive symptoms were assessed using the Center for Epidemiologic Studies-Depression (CES-D) scale. The results showed that the factors of project-management, mental-rewards, and job-overload had significant effect on depressive symptoms (p < 0.01). It is indicated for the first time that software project management affects depressive symptoms in systems managers.

Synthesis of 12(R)- and 12(S)-hydroxyeicosatetraenoic acid by porcine ocular tissues

Microsomal fractions from porcine ocular tissues synthesized 12(S)-5,8,10,14-hydroxyeicosatetraenoic acid [12(S)-HETE] from arachidonic acid by a membrane-bound lipoxygenase and 12(R)-HETE by the cytochrome P450-dependent monooxygenase system. Both activities were the highest in corneal microsomes. The 12(R)-HETE synthesizing activity of corneal microsomes was dependent on NADPH and inhibited by 0.1 mM SKF-525A, an inhibitor of P450 enzymes. The activity to form 12(R)-enantiomer was significantly enhanced by treatment of corneal epithelium with 3-methylcholanthrene or clofibrate. The induced activity was suppressed by cycloheximide, indicating that the induction of enzyme activities involved a translational process. The effect of these inducers on 12(R)-HETE synthesizing activity appeared to be additive. The activity to form 12(S)-enantiomer was markedly stimulated by 3 mM CaCl2. The 12-lipoxygenase of corneal microsomes was capable of oxygenating linoleic acid in addition to arachidonic acid, a characteristic of 12-lipoxygenases of the leukocyte type. 12(R)-HETE at 10(-6) M inhibited almost completely the Na,K-ATPase of corneal epithelium but had little or no effect on ciliary epithelial enzymic activity. 12(S)-HETE at 10(-6) M also inhibited corneal enzymic activity but to a lesser extent, and had no significant effect on ciliary epithelial Na,K-ATPase activity.

Identification of the cerebral motor cortex by focal magnetic stimulation: clinical application to neurosurgical patients

A figure-8 coil was designed that was capable of generating currents over a relatively limited area. In this study, we used the figure-8 coil to localize human cerebral motor cortex by transcranial magnetic stimulation and assessed its value as a diagnostic tool for neurosurgical disease. The subjects were 10 normal volunteers and 12 neurosurgical patients. The points obtaining a response were plotted and the response area was delineated for each stimulus output. Rectangular coordinates were subsequently determined for the C3-Cz-C4 line with the stimulation sites set 1.0 cm apart. Then amplitude and latency maps were displayed by a computer wave map program. In normal volunteers, the posterior margin of the site where a threshold +5% stimulus obtained a response from the THE or ADM muscles almost coincided with the central sulcus. The optimal areas were relatively narrow on the amplitude and latency maps. In the patient with a left frontal convexity meningioma, the left threshold +5% area for the THE and ADM muscles showed marked anterolateral shift. No threshold map could be obtained on the affected side in patients with metastatic tumor and astrocytoma. Low perfusion areas caused by moyamoya disease and arteriovenous malformations produced narrowing of the optimal zone on the threshold map of the affected side. Hyperexcitability of the motor cortex was recognized in the arteriovenous malformation patients. Transcranial focal magnetic stimulation is a useful noninvasive diagnostic method for identification of the human cerebral motor cortex. It provides important information about changes in the localization and excitability of the motor cortex in neurosurgical patients and should be helpful for treatment planning.

31P-magnetic resonance spectroscopic study on the effect of glycerol on cold-induced brain edema

The aim of the present study was to determine the effects of a hyperosmotic agent, 10% glycerol, on both brain energy metabolism and intracellular pH (pHi) in experimental vasogenic brain edema. Vasogenic brain edema was induced by cold injury applied to bilateral parietal portions in 13 mongrel dogs (7 glycerol, 6 control) while, 3 dogs were used as control. Before and at 24 hours after the injury, sequential phosphorous-31 magnetic resonance spectroscopy (31P-MRS) was performed for 2 hours in order to determine phosphocreatine (PCr), beta-adenosine triphosphate (beta-ATP), inorganic phosphate (Pi) levels and pHi. At 24 hours following cold injury, both PCr/Pi and ATP/Pi ratios significantly decreased from 7.75 to 3.97 and from 2.26 to 1.25, respectively. Furthermore, a moderate decrease in pHi of 7.16 to 7.01 was significantly demonstrated during the same experimental period. Administration of glycerol for 30 minutes significantly increased PCr/Pi from 3.97 to 5.06 and ATP/Pi from 1.25 to 1.72, respectively. Also, glycerol administration caused a significant increase in pHi from 7.01 to 7.11. This study indicates that cryogenic injury, in which formation and expansion of vasogenic brain edema a known to occur, results in disturbed brain energy metabolism and in intracellular acidosis; moreover, the administration of glycerol can ameliorate either or both of these derangements.

The mechanism of chlorpromazine-induced red blood cell swelling

1. Chlorpromazine (CPZ)-induced red blood cell (RBC) swelling was investigated by determination of electrolyte, mean cell volume (MCV) and water content changes in CPZ-treated cells. 2. CPZ-induced RBC swelling is dose-, hematocrit- and pH-dependent, and is associated with a net increase in RBC monovalent cation and Cl- contents. 3. The partition coefficient (Kp) for the CPZ-RBC membrane interaction is pH dependent (Kp = 2500 at pH 7.8; Kp = 840 at pH 6.8). 4. Despite the pH dependence of Kp values an equal number of CPZ molecules is required to induce a 12% increase in MCV at pH 7.8 and 6.8.

[Surgical results of postinfarction ventricular septal rupture]

Between 1981 and 1991, 17 consecutive patients underwent surgical repair of postinfarction ventricular septal rupture (VSR). 15 patients were operated upon during acute phase after the onset of VSR. Two patients were operated upon six weeks or more after the onset. Overall hospital mortality was 43% in the reviewed group. Our experience suggested that the number of the patients over 70 years of age increased and prevalence in VSR associated with the multivessel coronary artery disease was recognized. Despite improved surgical techniques and enhanced myocardial protection, our experience with surgical treatment of VSR was not as successful as we had hoped. Delay of operation is likely to produce hemodynamic instability and may increase operative mortality. In conclusion, the preoperative mechanical and pharmacological support should be performed, even if the patient is not so critically ill, and the earlier operation might lead to more favourable results in the surgery of the postmyocardial infarction ventricular septal rupture. In addition, preoperative coronary angiography for the precise evaluation of the coronary artery lesions might contribute to better results in the late phase of postoperative period.

Dose-dependent red blood cell volume increase induced by bepridil

1. Bepiridil, (beta-[(2-methylpropoxy)methyl]-N-phenyl-N-(phenyl-methyl)-1-py rro lidine-ethanamine), a calcium channel blocker, inhibits sickling of red blood cells (RBC) from patients with sickle cell disease (SCD) at micromolar concentrations in vitro. 2. Bepridil induces dose-dependent osmotic swelling of RBC and a concomitant decrease in mean corpuscular hemoglobin concentration (MCHC). 3. Modest decreases in MCHC greatly lengthen the delay time for polymerization of deoxygenated sickle hemoglobin (Hb S) and inhibit RBC sickling. 4. Equilibrium dialysis studies of bepridil and purified hemoglobin showed a low binding affinity (Kb = 10(3)/M). 5. The partition coefficient (Kp) determined for the interaction of RBC and bepridil was 1-3 x 10(3), which is similar to the Kp determined for other amphipathic molecules, such as chlorpromazine.

Image analysis studies of the degree of irreversible deformation of sickle cells in relation to cell density and Hb F level

We analyzed, quantitatively by image analysis, the degree of irreversible deformation of red cells (SS cells) from patients with homozygous sickle cell disease, and studied the relationships among the degree of irreversible cell deformation, cell density, and Hb F level. SS cells from 25 patients (aged 1-36 years) whose Hb F levels ranged from 2.5% to 40.0%, were fully oxygenated and then were separated into four fractions by density centrifugation. Every fraction was studied for morphology and Hb F content. We found that the irreversible deformation of SS cells from the circulation occurred mainly by elongation and that the degree of elongation was extremely variable. We also found that in the cells of patients with Hb F levels < 20% the degree of irreversible elongation increases as cell density increases, suggesting that dehydration occurs concomitantly with irreversible elongation. Statistical analysis (Student t test) indicated that there were significant differences (P = 0.008 or < 0.001) in the degree of elongation among density-fractionated SS cells from patients with Hb F < 20%, although there was no significant difference (P > 0.1) among those from patients with Hb F > or = 20%. We also found that cell density increased as Hb F level of the density fraction decreased in all patients with Hb F < 20% but not always in those with Hb F > or = 20%. This suggests that cells with lower Hb F levels are selectively susceptible to dehydration. Furthermore, we found that the mean degree of irreversible elongation decreases linearly with increasing levels of Hb F and reaches the normal range at 21-24%. Since the degree of irreversible deformation of SS cells quantified by image analysis is directly related to cell density, and inversely to Hb F levels, mechanical stress or membrane damage caused by Hb S polymerization may be an important factor in the formation of dense cells in vivo.

Diminution of biological reactivity of ethanol by changing the solution structure by weak ultrasonication

The weak ultrasonication (40 kHz, 12 mW, 1 week) of ethanol solutions was found to reduce stimulation of the senses of smell and taste by the ethanol on the basis of blind tests with an aqueous ethanol solution (33.0% w/v) and an immature distilled spirit (25.0% v/v). Experiments on mice also demonstrated that a treated aqueous ethanol solution had a weaker depressant effect on the central nervous system, as evaluated by the relative frequency with which mice regained the righting reflex at a dose of either 4.0 or 4.5 g/kg (p < 0.05 or p < 0.01, respectively) and by the reduction in rectal temperature at a dose of 5.0 g/kg (p < 0.05) soon after ethanol administration. Analyses of both the ethanol concentration by head-space gas chromatography and the free radicals by electron spin resonance spectrometer failed to reveal any chemical changes in aqueous ethanol solutions subjected to weak ultrasonication. However, measurement of the spin-lattice relaxation time (T1) of the 2H of water molecules by 2H-NMR showed that the treatment slightly accelerated the thermal motion of water molecules in the solutions. Treated solutions were also found to have a slightly higher density than untreated ones. These physical data demonstrate that weak ultrasonication induces a structural change, such as a more compact and homogeneous structure by changing the microdynamic behavior of the solution. These biological and physical studies suggest that only a slight structural change in an ethanol solution induces a marked change in the biological reactivity of ethanol without any chemical modification of the solution itself.

Re-evaluation of solid-phase adsorption and desorption techniques for isolation of trace organic pollutants from chlorinated water

Amberlite XAD resin and activated carbon columns were tested for their abilities to concentrate trace organic pollutants in chlorinated water. Both XAD-2 and XAD-7 resin columns (20 ml) were capable of adsorbing about 30% of total organic halogen (TOX) present in 20 l of drinking water (pH 7) containing about 100 micrograms/l of TOX, whereas the carbon column (10 ml) adsorbed over 90% of TOX. The adsorption capacity of XAD-7 resin was found to be strongly dependent on the solution pH, as compared with those of XAD-2 and carbon adsorbents. Soxhlet and sonication extractions were also evaluated for their abilities to recover the adsorbed organics from the adsorbents, by measurements of TOX, chromatographable compounds and mutagenicity in the eluates. Soxhlet extraction gave higher recoveries than sonication, as measured with the above indices, but these differences were generally small (ca. 20%), with exception of the carbon extracts. The XAD-2 and XAD-7 extracts of drinking water also showed about 3-4 times higher mutagenic activity than the carbon extracts.

Neurons containing gastrin releasing peptide-like immunoreactivity in the human pancreas

Gastrin releasing peptide (GRP) is known to stimulate pancreatic enzyme and islet hormone secretion. In the present immunohistochemical study, the localization and distribution of GRP-like immunoreactivity were investigated in the human pancreas using two antisera with different specificities. GRP-like immunoreactivity (GRP-LI) was observed in numerous nerve fibers diffusely distributed to the exocrine pancreas, but was not seen in intrapancreatic nerve cells of normal pancreatic specimens examined. Nerve fibers and terminals with GRP-LI were found in abundance around pancreatic acini and capillaries, with moderate density around ductules and in the walls of arterioles, and a few were seen in islets. This distribution pattern was quite similar to that of vasoactive intestinal polypeptide (VIP)-LI nerve fibers. The study, using the antibody elution method, strongly suggests the co-localization of GRP- and VIP-LIs within a part of VIP-containing nerve fibers. In the chronic pancreatitis specimens, neurons with GRP-LI were frequently found, and > 90% of intrapancreatic nerve cells were VIP-immunoreactive. Immunostainings for GRP and for VIP on serial adjacent sections of intrapancreatic ganglia from chronic pancreatitis specimens suggested the co-localization of the two immunoreactivities in > 70% of intrapancreatic neurons. The present findings may provide a morphological basis for neurotransmitter and/or neuromodulator roles of GRP in the human pancreas.

Comparative studies of phenothiazine derivatives for their effects on swelling of normal and sickle erythrocytes

1. Three phenothiazines with similar structure; chlorpromazine (CPZ), triflupromazine (TFPZ), and trifluoperazine (TFP), were compared for the potency of swelling of normal red cells and antisickling effect of red cell from patients with sickle cell disease. 2. Normal erythrocytes treated with the phenothiazines became swollen within 60 min, and the percent increase in mean cell volume (MCV) was dose-dependent and varied according to the agent used. 3. The cell swelling was hematocrit-dependent, and pH-dependent. A greater swelling potency was seen at lower hematocrits and higher pH values. 4. The swelling was also dependent on the pKa values of these chemicals. TFP with the lowest pKa induced the highest degree of swelling while CPZ with the highest pKa induced the lowest. 5. The un-ionized fraction of the phenothiazines at a given pH was directly related to potency of the swelling. 6. The cell swelling was directly related to the binding affinities of the phenothiazines to calmodulin. 7. The antisickling effect of these compounds using sickle red cells, numerically estimated by an automated image analysis system, was found in the same order as that of swelling potency: TFP > TFPR > CPZ.

[Retrograde systemic venous perfusion with selective jugular cannulation]

46 patients underwent surgery for the ascending aorta and the aortic arch using continuous hypothermic retrograde systemic venous perfusion (RSVP). Good cerebral protection has been obtained by this method in most patients including four in whom periods of retrograde perfusion exceeded 90 minutes (the longest 140 min). In first 19 patients retrograde perfusion was performed through conventional caval cannulae, but one of them sustained serious neurological damage despite a relatively short duration of retrograde perfusion probably due to impediment of retrograde flow to the brain with venous valves at the jugular-subclavian junction. Then we have developed a new technique that employs a cavoatrial cannula inserted selectively into the internal jugular vein beyond the valve at the venous angle and have applied this technique in last 27 patients.

Pulse oximetry and factors associated with hemoglobin oxygen desaturation in children with sickle cell disease

The observation of low transcutaneous arterial oxygen saturation (SaO2) in otherwise well sickle cell patients has lead to questions about the interpretation of pulse oximetry values in these patients. We undertook a prospective study of children with sickle cell disease to (1) determine the prevalence of, and factors associated with, low transcutaneous SaO2 in clinically well patients, (2) develop an algorithm for the use of pulse oximetry in acutely ill patients, and (3) assess the accuracy of pulse oximetry in these patients. Eighty-six clinically well children with hemoglobin (Hb) SS had a lower mean transcutaneous SaO2 than 22 Hb SC patients and 10 control subjects (95.6% v 99.1% v 99.0%, respectively; p < .001). In Hb SS patients, a history of acute chest syndrome and age greater than 5 years were associated with lower transcutaneous SaO2 (mean 93.8% for those with a history of acute chest syndrome v 97.8% for those without a history of acute chest syndrome, and 94.0% for patients > 5 years old v 97.2% for those < or = 5 years old; P < .001). These associations were not seen in Hb SC patients. During acute illness, Hb SS patients with acute chest syndrome had transcutaneous SaO2 values that were less than 96% and at least 3 points lower than measurements made when they were well. A nomogram was designed to aid in the interpretation of transcutaneous SaO2 in acutely ill Hb SS patients when a comparison value is not available. The accuracy of pulse oximetry was shown by the correlation between SaO2 measured by pulse oximetry and calculated by using the patient's oxygen dissociation curve and PaO2 (r = .97). This study provides evidence that Hb oxygen desaturation is not a universal finding among children with sickle cell disease and identifies factors associated with Hb oxygen desaturation. We conclude that pulse oximetry may be useful to assess whether progressive pulmonary dysfunction begins at an early age in Hb SS patients, and to assess acutely ill patients for the presence of hypoxemia associated with acute chest syndrome.

Statistical properties of the Fraunhofer diffraction field produced by random fractals

First-order statistical properties of the speckle field and its intensity in the Fraunhofer diffraction region that is produced by random Koch fractals are investigated by means of computer simulations in comparison with the ordinary fully developed speckle.

A method for studying the structure of uniaxially aligned biopolymers using solid state 15N-nmr: application to Bombyx mori silk fibroin fibers

Recent advances in the application of solid state nmr spectroscopy to uniformly aligned biopolymers have opened a window through which to view the detailed structure of biological macromolecules that are unable to be seen with standard techniques for structure determination such as x-ray diffraction. Atomic resolution structural details are obtained from solid state nmr data in the form of bond orientations, which yield the relative positions of specific atoms within the molecule. For static aligned systems such as fibers, in which rapid reorientation about the axis of alignment does not occur, it has generally been necessary to perform trial and error line-shape simulations to extract structural details from nmr spectra arising from a single type of nuclear spin interaction. In the present work, a new method is developed in which solid state 15N-nmr spectra obtained from uniaxially aligned molecules placed with the axis of alignment both parallel and perpendicular to the magnetic field are analyzed to yield the orientations of specific molecular bonds. Analytical expressions are derived that utilize spectral features read from 15N chemical shift anisotropy line shapes to calculate a discrete number of possible orientations for a specific site. The 15N-1H dipolar interaction is employed to further narrow the number of unique orientations possible for a given site. With this method, a neighborhood of possible orientations is quickly determined, and full line-shape simulations within this region of allowed space can be performed to refine the limits of orientation. This technique demonstrates the use of a single type of isotopic label to determine the orientation of a specific molecular group such as a peptide plane within a protein. Results from the application of this method to the Bombyx mori silk fibroin protein provide structural detail that is consistent with currently accepted structural models based on fiber diffraction studies.