[Revision operations after tenotomy of the medial rectus muscle]

BACKGROUND

Although tenotomy of the medial rectus (MR) is generally regarded to be obsolete, consecutive exotropia after this procedure, requiring a reoperation, still occurs.

PATIENTS AND METHODS

In 143 patients a reoperation after tenotomy of the MR had to be performed because of consecutive exotropia. Either only the MR was sutured at the original insertion (advancement; this constitutes group 1, n = 101) or the lateral rectus (LR) was recessed in addition (group 2, n = 12). The recession of the LR was only added if the adduction was not distinctly limited and if the distance of the MR from the limbus was less than 16 mm. We wanted to find out whether the procedure in group 1 or 2 gave the better results.

RESULTS

In group 1 the muscle sheath of the MR was found at a distance of 7 mm (median), the muscle itself at a distance of 18 mm from the limbus (confidence interval 13.5-25 mm). In group 2 the distance of the muscle sheath from the limbus was similar to group 1, the muscle itself was found already at a distance of 12 mm from the limbus (confidence interval 6-18 mm). After reinsertion of the muscle at the original insertion without recession of the LR, a distinct limitation of abduction combined with a globe retraction was seen immediately after surgery. A spontaneous release of the old contracture reduced these troublesome side effects. Three months postoperatively the initial surgical effect had diminished to 83%. The average postoperative squint angle was -3 degrees at 5 m and -4 degrees at 0.33 m with a high scatter. In group 1 [group 2 in brackets], the range of the horizontal motility was improved by 15 degrees [10 degrees] (median) and the incomitance, i.e. the difference between the angle of squint at 25 degrees gaze to the right and to the left, by 4 degrees [0 degrees, i.e. no improvement]. Thus, this postoperative improvement was smaller in cases of simultaneous recession of the LR (group 2).

DISCUSSION

The most important aim in a reoperation after tenotomy of the MR is to find the muscle itself and to suture it to the original insertion. It can be expected that the contracture of the MR will loosen when the muscle is put under increased tension. This effect will be less if the LR is recessed in addition to the advancement of the MR. Consistent with this assumption, our not randomized, retrospective study revealed a better horizontal motility after advancement of the MR alone. Because of the difficulties in revising a tenotomy, we strongly advise a graded recession rather than any form of tenotomy.

Effect of recombinant erythropoietin on anemia and orthostatic hypotension in primary autonomic failure

Anemia is a common complication of autonomic failure and reduced red blood cell mass may contribute to the orthostatic hypotension of these patients. We investigated whether treatment with recombinant erythropoietin improves anemia and increases blood pressure in patients with primary autonomic failure. Three patients with multiple system atrophy and autonomic failure and one with pure autonomic failure were studied. All patients had normocytic normochromic anemia and low (n = 2) or normal (n = 2) serum levels of erythropoietin. Treatment with erythropoietin, 4000 U subcutaneously biweekly for 6 weeks, increased hematocrit and blood pressure in all patients. Hematocrit increased from 33.9 +/- 0.7 to 44.3 +/- 1.4%, blood pressure in supine position increased from 150 +/- 8/87 +/- 8 (systolic/diastolic; mean +/- SD) to 166 +/- 25/92 +/- 12 mmHg, and after 3 min in the head-up tilt position from 86 +/- 21/47 +/- 15 to 102 +/- 23/63 +/- 12 mmHg, (p < 0.05). All patients reported improvement in orthostatic symptoms and increased tolerance to standing. The study shows that treatment with erythropoietin improves anemia, increases blood pressure and ameliorates orthostatic hypotension in patients with primary autonomic failure.

[Motor blockade by retrobulbar anesthesia. Phenomenology and mechanism of action]

The aim of this study was to analyze quantitatively the phenomenology and mechanisms of motor blockade induced by retrobulbar anesthesia (RETRO).

PATIENTS AND METHODS

Prior to cataract surgery, 34 patients received RETRO using the intraconal technique of Atkinson. Four milliliters of mepivacaine 2% (Scandicain), prilocaine 2% (Xylonest) or lidocaine 2% (Xylocain) were injected in randomized order. Prior to injection, as well as 5, 30, 90, 120, 180, 300 and 420 min after injection, the following variables were determined: deviation of the eye from the primary position (Krimsky test), horizontal and vertical ocular motility (Kestenbaum limbustest), and rotatory ocular motility (presence of in- or excycloductions).

RESULTS

The directions in which the eye deviated after RETRO were abduction and depression. The maximum deviations amounted to 7-8 degrees abduction and 3-4.5 degrees depression and were observed 30 min after injection. Horizontal and vertical ocular motility was nearly completely and symmetrically reduced 30 min after RETRO. There were no significant differences between the three local anesthetics used.

DISCUSSION

The present findings may be interpreted as temporary palsy of N.III and N.VI during RETRO (symmetrical blockade of horizontal and vertical recti eye muscles) with unaffected function of N.IV and superior oblique muscle (maintained incycloduction ability; hypotropia and exotropia). An additional possible mechanism to account for the observed downward deviation is that the eye assumes its physiological divergent resting position during RETRO.

Neurally mediated syncope: pathogenesis, diagnosis, and treatment

Neurally mediated syncope is the most frequent cause of syncope in patients who do not have structural heart disease. Neurally mediated syncope is believed to be a reflex triggered by excessive afferent discharge from mechanoreceptors located in the arterial tree or viscera, particularly the left ventricle of the heart. In response to these signals, a CNS-mediated sudden rise in parasympathetic efferent activity occurs, causing relative or absolute bradycardia and sympathoinhibition with arterial vasodilation and hypotension. Although our understanding of the pathophysiology of this syndrome is still incomplete, it is well established that sympathetic nerve activity and norepinephrine release fall inappropriately during neurally mediated syncope, whereas appropriate increases in plasma concentrations of epinephrine, angiotensin II, vasopressin, and endothelin-1 occur. Recent studies from our laboratory suggest that synthesis of the vasodilator nitric oxide increases during neurally mediated syncope. This suggests that nitric oxide-mediated arterial vasodilation could contribute to the profound hypotension characteristic of this syndrome. The diagnosis of neurally mediated syncope can be made with acceptable levels of specificity and sensitivity by the upright tilt test. Explaining the mechanisms responsible for arterial vasodilation in neurally mediated syncope may lead to effective treatment.

[A new method for objective vision assessment using infrared nystagmography]

Objective assessment of visual acuity (VA) is necessary in cases of malingering or poor cooperation in subjective VA evaluation. Based on Ohm's idea of the suppression of experimentally evoked optokinetic nystagmus (OKN), a new objective visual acuity test is presented. A commercially available system for monitoring eye movement (OBER2) allows the test to be performed on a standard PC with a minimum amount of time. A grating pattern moving horizontally on the screen evokes OKN, which is recorded by infrared nystagmography. Superimposed black optotypes of increasing size (brake marks) suppress OKN as soon as they are recognized. Eighty-two normal eyes with VA artificially reduced by different Bangerter dispersion foils (VA 0.04-1.6) and 152 eyes with visual disturbances (VA 0.04-1.0) of various etiologies were examined. The test allowed estimation of the least VA in steps of > or = 1.0, > or = 0.25, > or = 0.1, > or = 0.05. None of the eyes examined had a VA below these values when the OKN was suppressed by the referring brake mark.

[Combined oblique muscle operation with transposition of the insertion in strabismus sursoadductorius]

BACKGROUND

The combined superior oblique tendon tuck and inferior oblique recession is the method of choice for the treatment of congenital and acquired superior oblique muscle palsies with large vertical and cyclodeviations. An additional transposition of the insertions is indicated if the vertical deviation differs greatly from the excyclodeviation.

PATIENTS AND METHODS

38 patients who underwent combined oblique muscle surgery for congenital superior oblique muscle palsy were divided into 3 groups. Group A: 14 patients with small excyclodeviations in spite of large vertical deviations, even after diagnostic occlusion of 3 days. A superior oblique tendon tuck of 5 or 6 mm with transposition of the new insertion to the posterior margin of the original insertion was performed combined with a recession of the inferior oblique muscle of 5 or 6 mm with anterior displacement of 4-6 mm. Group B: 15 patients without a discrepancy between the vertical deviation and the cyclodeviation. They were treated with a conventional superior oblique tendon tuck of 5 or 6 mm combined with a recession of the inferior oblique muscle. Group C: 9 patients without a discrepancy between the vertical deviation and the cyclodeviation, but deviations smaller than in group B. A conventional superior oblique tendon tuck of 6 mm combined with a posterior tenotomy of the inferior oblique muscle was performed. The surgical effect was calculated as the difference between the preoperative deviation after diagnostic occlusion of 3 days and the postoperative deviations (1 week and 3 to 6 months). All angles of deviation were measured subjectively after dissociation of the binocular vision with a dark red filter in front of the fixating, not affected eye at 2.5 m distance using the Harms tangent screen.

RESULTS

3 months postoperatively, the vertical deviation was diminished in primary position by 12.1 degrees/6.8 degrees/6.8 degrees in groups A/B/C, in 25 degrees adduction of the affected eye by 18.4 degrees/13.8 degrees/9.5 degrees. The reduction of the cyclodeviation in primary position was 6.4 degrees/8.0 degrees/5.6 degrees. As a side effect a clinically insignificant, consecutive Brown syndrome occurred in each group. In each group a significant positive correlation between the preoperative deviation and the surgical effect was found.

CONCLUSIONS

The combined superior oblique tendon tuck and inferior oblique recession with transposition of the insertions is a suitable method for a selective treatment of the vertical deviation and the cyclodeviation in congenital superior oblique palsy.

[The Stilling-Türk-Duane retraction syndrome]

The typical symptoms of Retraction syndrome (Stilling-Türk-Duane) are severe limitation of abduction, slight limitation of adduction and convergence, which are always accompanied by retraction of the globe, narrowing of the palpebral fissure, vertical deviation and elevated intraocular pressure, and a remarkable motility of the globe in the orbital axis. All symptoms are explicable by the cocontraction of the horizontal rectus muscles. In cases of single binocular vision, surgery is indicated only when the head posture is intolerable. We restrict surgery to recession of horizontal rectus muscles according to the head posture and the deviation. The surgical results of this procedure are satisfactory concerning the horizontal and the vertical deviation and the head posture.

[Effect of axial bulbus length and preoperative squint angle on the effect of horizontal combined squint operations]

We studied the influence of axial bulbus length on the effect of the recession/resection procedure in 175 patients and found a significant negative correlation between the axial length and surgical effect in 62 esotropic patients undergoing surgery of various degrees. A poor correlation was found in 69 exotropic patients. In a group of 54 patients who underwent recession/resection surgery for esotropia with 5 mm recession of the medial rectus muscle and 7 mm resection of the lateral rectus muscle there was a highly significant correlation between the axial length and effect. There was also a significant correlation between the angle of the preoperative deviation and the response to surgery in the esotropic groups. To reduce the variability of strabismus surgery the bulbus length should be taken into consideration, at least in recession/resection procedures when the surgery exceeds 10 mm.

[Effect of bulbus length of reduction of squint angle after suture fixation]

The principle of the posterior fixation suture popularized by Cüppers in 1971 is to decrease the length of the lever arm. The latter depends on the radius of the globe. For geometric reasons the axial length should have an influence on the surgical effect. There are contradictory results on this problem. Therefore, we conducted a study including 112 patients mainly with non-accommodative convergence excess (average age: 7.0 years, average axial length: 21.7 mm). We measured the axial length of both eyes before performing a retroequatorial myopexy. The amount of symmetrical surgery done in both eyes averaged between 12.0 and 14.0 mm, measuring 5.5 mm behind the limbus, i.e., from the insertion of the medial rectus. Fifty of the 112 patients received additional recession or resection of the medial rectus in one or both eyes. A statistically highly significant negative correlation was found between the axial length and the response to strabismus surgery (surgical effect = reduction of near and distance deviation). The correlation coefficient ranged between -0.29 (for all 112 patients) and -0.69 (for the uniform group of 24 patients with 13 mm surgery) with P < 0.0001. The same correlation was evident between the point of the posterior fixation suture behind the equator (angle of "retroequatoriality" in degrees) and the response to strabismus surgery. It is well known fact that larger deviation show a greater response to posterior fixation sutures.(ABSTRACT TRUNCATED AT 250 WORDS)

[Results of surgical treatment of Stilling-Türk-Duane retraction syndrome]

BACKGROUND

The typical signs of the retraction syndrome (Stilling-Türk-Duane) are abnormal head posture, marked limitation of abduction, slight limitation of adduction and convergence, which are always accompanied by retraction of the globe, narrowing of the palpebral fissure, vertical deviation and increased intraocular pressure upon adduction. All signs are explicable by the co-contraction of the horizontal muscles or the failing relaxation of the lateral rectus muscle. Abnormal synergistic innervation occurs when in aplasia of the abducens nerve the lateral rectus muscle receives abnormal innervation by branches of the oculomotor nerve, which may also be accompanied by fibrosis of those parts of the muscle that are not innervated. This pathogenesis gives reason for the variety of signs and reduces the value of all classifications defined by electromyography. It seems more sensible to classify the retraction syndrome with respect to the direction of the head turn.

PATIENTS AND METHODS

According to this classification, the left-sided retraction syndrome with head turn in adduction made up the largest, typical group (58%) in our study (n = 82). All other groups represented less than 12%. The main goal of surgical therapy was the elimination of the abnormal head turn, the vertical deviation and the retraction. Based on the pathogenesis, only recessions of one or both horizontal muscles were performed and strengthening procedures were avoided.

RESULTS

Concerning the horizontal and vertical deviation and the head posture, the surgical results of this procedure were satisfactory. Preoperatively less than 10% in all groups showed a deviation at distance of 5 degrees and less, whereas 6 month after surgery this small angle was obtained in over 60% in all groups. While preoperatively less than 20% in all groups had a head turn of 10 degrees and under at distance fixation, 6 months after surgery this was demonstrated in over 70% of all our cases.

CONCLUSION

The main goal of surgery is the reduction of the abnormal head posture, the retraction with narrowing of the palpebral fissure and the vertical deviation. Only recessions of one or both horizontal muscles can achieve the necessary mechanical relief. In cases with marked retraction one must avoid strengthening procedures.

The most abundant soluble basic protein of the stylar transmitting tract in potato (Solanum tuberosum L.) is an endochitinase

An abundant, pistil-specific basic protein has been purified and characterized from potato (Solanum tuberosum L.). A polymerase chain reaction (PCR) probe was generated for the corresponding gene using oligonucleotides based on internal peptide sequences of the protein, and the PCR probe was further employed to isolate cDNA and genomic clones. The sequence of the gene exhibits up to 70% similarity to previously described endochitinase class 1a protein sequences, and the purified protein possesses chitinase (poly[1, 4-(N-acetyl-beta-D-glucosaminide)] glucanohydrolase, EC 3.2.1.14) activity. The protein, termed SK2, has been located by immunocytochemistry to the intercellular matrix of the stylar transmitting tract. Immunoblot analysis has shown SK2 to be distinct from the wound-induced chitinases of potato. The SK2-class of chitinase is restricted in its distribution within the Solanaceae to the sub-family Solanoidae, which includes cultivated tomato and potato species. It was absent from the Cestroidae species tested (Petunia hybrida, Nicotiana tabacum). A role for SK2 endochitinase in protecting the ovary against pollen-tube-mediated pathogen ingress is proposed.

DNA probes for the detection of Fasciola hepatica in snails

Fasciola hepatica, also called the large liver fluke, is a trematode which can infect most mammals. Monitoring the infection rate of snails, which function as intermediate hosts and harbour larval stages of F. hepatica, is an important component of epidemiological studies on fascioliasis. For this purpose, DNA probes were generated which can be used for the detection of F. hepatica larvae in snails. Four highly repetitive DNA fragments were cloned in a plasmid vector and tested by Southern blot hybridization to the DNA of various trematodes for specificity and sensitivity. The probes Fhr-I, Fhr-II and Fhr-III hybridized only to F. hepatica DNA. Fhr-IV contained ribosomal RNA gene sequences and cross-hybridize with the DNA from various other trematode species. Squash blot analysis showed that the different probes were able to detect the parasite larvae in trematode-infected snails even as isolated single larvae. No signals were obtained in squash blots of uninfected snails. Probes Fhr-I, Fhr-II and Fhr-III are thus useful specific tools for studying the epidemiology of fascioliasis. The probe Fhr-IV, because of its broader spectrum, can be used to detect the larvae of a wide range of trematode species of waterbirds, which are the causative agents of swimmer's itch.

Neurogenic orthostatic hypotension: a double-blind, placebo-controlled study with midodrine

PURPOSE

To investigate the efficacy and safety of midodrine for treatment of patients with orthostatic hypotension due to autonomic failure.

PATIENTS

Ninety-seven patients with orthostatic hypotension were randomized in a 4-week, double-blinded, placebo-controlled study with a 1-week placebo run-in period. Patients ranged in age from 22 to 86 years (mean: 61 years).

METHODS

After a 1-week run-in phase, either placebo or midodrine at a dose of 2.5 mg, 5 mg, or 10 mg was administered three times a day for 4 weeks. Both the placebo group and the 2.5-mg midodrine group received constant doses throughout the double-blind phase. The patients receiving 5 mg or 10 mg of midodrine were given doses that were increased at weekly intervals by 2.5-mg increments until the designated dose was reached. Efficacy evaluations were based on an improvement at 1-hour postdose in standing systolic blood pressure and in symptoms of orthostatic hypotension (syncope, dizziness/lightheadedness, weakness/fatigue, and low energy level).

RESULTS

Midodrine (10 mg) increased standing systolic blood pressure by 22 mm Hg (28%, p < 0.001 versus placebo). Midodrine improved (p < 0.05) the following symptoms of orthostatic hypotension compared to placebo: dizziness/lightheadedness, weakness/fatigue, syncope, low energy level, impaired ability to stand, and feelings of depression. The overall side effects were mainly mild to moderate. One or more side effects were reported by 22% of the placebo group compared with 27% of the midodrine-treated group. Scalp pruritus/tingling, which was reported by 10 of 74 (13.5%) of the midodrine-treated patients, was most frequent. Other reported side effects included supine hypertension (8%) and feelings of urinary urgency (4%).

CONCLUSION

We conclude that midodrine is an effective and well-tolerated treatment for moderate-to-severe orthostatic hypotension associated with autonomic failure.

[The radiological findings in adamantinoma of the long tubular bones]

The radiological findings of adamantinomas of long bones are described in 22 patients. The diagnosis was confirmed by a team of experts (pathologist, radiologist, orthopaedic surgeon) of the "Bone tumour study group" at the German Cancer Research Center. There were 12 male and 10 female patients aged 5 to 67 years (most commonly in the second and third decade). In 21 patients the tibia was involved and in one patient the fibula. The tumour was nearly always in the diaphysis (20 cases). The most striking radiological feature was a diaphyseal lesion confined to the bone showing multicentric translucencies. The latter showed surrounding or central ring shaped or focal areas of increased density. The lesions tended to be longitudinal, averaging 11 cm (between 3 and 25 cm). All lesions showed a sclerotic margin separating it from normal bone, at least over part of the lesion. Expanding lesions were mostly separated from the soft tissues by a bony rim (18 cases).

Hypotension-induced vasopressin release distinguishes between pure autonomic failure and multiple system atrophy with autonomic failure

To investigate whether activation of afferent and central baroreceptor pathways could differentiate between pure autonomic failure (PAF) and multiple system atrophy with autonomic failure (MSA), we determined the effect of upright tilt on circulating levels of vasopressin in patients with PAF and patients with MSA. We also studied 14 normal subjects, nine of whom developed acute hypotension due to vasovagal syncope. In patients with PAF and in normal subjects with vasovagal syncope, upright tilt induced marked hypotension and a pronounced increase in the plasma concentration of vasopressin (1.1 +/- 0.3 to 38.0 +/- 8.0 pmol/l in PAF and 1.0 +/- 0.2 to 27.4 +/- 7.2 pmol/l in vasovagal syncope, p less than 0.005 for both). In patients with MSA, upright tilt also elicited profound hypotension but circulating levels of vasopressin increased little (0.5 +/- 0.1 to 1.5 +/- 0.3 pmol/l, p less than 0.05). During upright tilt, the plasma concentration of norepinephrine significantly increased in normal subjects but did not increase in patients with autonomic failure. Our results indicate that afferent and central baroreceptor pathways involved in vasopressin release are normal in patients with PAF but are impaired in patients with MSA. Thus, measurement of baroreceptor-mediated vasopressin release appears to provide a clear marker to differentiate between patients with PAF and patients with MSA.

Reduced chemical and radioactive liquid waste during electrophoresis using polymerized electrode gels

Using polyacrylamide electrode gels during horizontal sodium lauryl sulfate-polyacrylamide electrophoresis of radiolabeled proteins instead of electrode papers reaching into electrode buffer reservoirs, silver staining is improved and we reduce chemical and radioactive liquid waste during electrophoresis.

Plasma endothelin during upright tilt: relevance for orthostatic hypotension?

Since plasma endothelin concentration increases with upright posture and decreases with volume expansion, a study was conducted to test whether activation of the baroreceptor reflex releases endothelin into plasma. The effect of passive upright tilt on the plasma concentrations of endothelin and vasopressin was examined in: (1) normal subjects; (2) patients with impaired baroreceptor reflex due to primary autonomic failure; (3) patients with normal afferent baroreceptor function but acute inhibition of vasoconstrictor sympathetic outflow (ie, with vasovagal syncope); and (4) patients with hypophysial diabetes insipidus. In normal subjects, upright tilt did not change arterial pressure and significantly increased the plasma concentrations of endothelin and vasopressin. In patients with autonomic failure, upright tilt induced a considerable fall in arterial pressure, no rise in plasma endothelin, and a slight increase in plasma vasopressin. In subjects with vasovagal syncope, arterial pressure dropped and the plasma concentrations of endothelin and vasopressin rose. In the subjects with diabetes insipidus, arterial pressure fell slightly, without change in plasma concentration of endothelin. The results suggest that activation of the baroreceptor reflex induces the release of endothelin into plasma, probably from the neurohypophysis, and they raise the possibility that impaired endothelin release contributes to the orthostatic hypotension of patients with primary autonomic failure.

[Changes in ocular circulation in halothane-nitrous oxide intubation anesthesia with special reference to the arterial CO2 partial pressure. II. Mechanisms of change]

In part I of this study [Hessemer and associates, Klin. Mbl. Augenheilk. 199 (1991) 346-355] the phenomenology of the ocular circulatory changes, found during general anesthesia using halothane and nitrous oxide, has been described. These changes are analyzed with respect to their mechanisms.--

RESULTS

There was a significantly (P less than 0.05) linear relation between the anesthesia-induced reduction of the systolic ocular (retinal and ciliary) blood pressures and the decrease of the systolic brachial artery pressure (delta Ps,bra). The same relation was present between the reduction of the systolic ocular (retinal and ciliary) perfusion pressures and delta Ps,bra. The correlation coefficients for the designated relations ranged between 0.37 and 0.58. The relation between the anesthesia-induced intraocular pressure reduction and delta Ps,bra was--in tendency--linear (P = 0.07), at least for the time period 5-15 min after intubation; the correlation coefficient amounted to 0.37. The reduction of both the ocular pulsation volume (PVoc) and the pulsatile ocular blood flow (Fp,oc) did not depend on the systemic blood pressure, but on the arterial CO2 tension (PCO2): Decreasing PCO2--i.e., increasing hyperventilation--was paralleled by decreases of PVoc and Fp,oc. The relations PVoc vs. PCO2 and Fp,oc vs. PCO2 were significantly linear (P less than 0.01), the correlation coefficients ranged between 0.58 and 0.7.(ABSTRACT TRUNCATED AT 250 WORDS)

[Ocular circulatory changes in halothane-nitrous oxide intubation anesthesia with special reference to arterial CO2 partial pressure. I. Phenomenology of changes]

In 20 patients (5 with cataract, 15 with strabismus), general anesthesia was performed using halothane (inspiratory concentration: 0.5 vol.%) and nitrous oxide (65 vol.%); thiopental was employed for induction of anesthesia, vecuronium and succinylcholine were used for neuromuscular blockade prior to intubation. In series 1, the patients were slightly hyperventilated (PCO2 33 mmHg, on average). In series 2, the arterial PCO2 was changed in a range between 20 and 45 mmHg. By means of oculo-oscillo-dynamography, we determined the systolic retinal and ciliary perfusion pressures (PPs,ret and PPs,cil) as well as the respective ocular blood pressures (Ps,ret and Ps,cil), the ocular pulsation volume (PVoc) and the pulsatile ocular blood flow (Fp,oc = PVoc x heart rate). The intraocular pressure (Pio) was measured with the Draeger hand-applanation tonometer. Results of series 1: Measured 5 and 15 min after intubation, PPs,ret was reduced by averages of 12.5 and 20.2 mmHg, respectively, corresponding to decreases of 13.1 and 21.2% compared to the initial values. Ps,ret was decreased by 15.4 mmHg (14.2%) 5 min after intubation and by 27.1 mmHg (25.0%) 15 min after intubation. The ciliary pressures (PPs,cil and Ps,cil) were changed by similar amounts. PVoc was reduced by 0.3 microliters (50.8%) during both time periods after intubation. Fp,oc was lowered by 19.5 microliters/min (41.0%) and by 26.4 microliters/min (55.5%), measured 5 and 15 min after intubation, respectively. Pio was decreased by 1.6 mmHg (11.3%) and by 7.6 mmHg (53.5%), respectively. The systolic brachial artery pressure was reduced by 12.6 mmHg (9.5%) 5 min after intubation and by 29.1 mmHg (21.9%) 15 min after intubation. The diastolic branchial artery pressure showed a slight initial increase, followed by a small decrease. All changes were highly significant (P less than 0.001; 1-factor analysis of variance plus Scheffé test). Results of series 2: In a PCO2 range between 40 and 45 mmHg (normo-until slight hypoventilation; determined 5 min after intubation), PVoc and Fp,oc averaged 0.43 microliter and 42.9 microliters/min, respectively. In a PCO2 range between 30 and 35 mmHg (slight hyperventilation), PVoc and Fp,oc averaged 0.38 microliters and 36.1 microliters/min, respectively; and in a PCO2 range between 20 and 25 mmHg (forced hyperventilation), they averaged 0.21 microliter and 22.8 microliters/min, respectively. All other variables were not dependent on the PCO2 level.

CONCLUSIONS

The lowering of PVoc and Fp,oc, observed during halothane-nitrous oxide anesthesia--especially with forced hyperventilation-, may be interpreted as reduced pulsatile choroidal blood flow.(ABSTRACT TRUNCATED AT 400 WORDS)

RFLP maps of potato and their alignment with the homoeologous tomato genome

An RFLP linkage map of the potato is presented which comprises 304 loci derived from 230 DNA probes and one morphological marker (tuber skin color). The self-incompatibility locus of potato was mapped to chromosome I, which is homoeologous to tomato chromosome I. By mapping chromosome-specific tomato RFLP markers in potato and, vice versa, potato markers in tomato, the different potato and tomato RFLP maps were aligned to each other and the similarity of the potato and tomato genome was confirmed. The numbers given to the 12 potato chromosomes are now in accordance with the established tomato nomenclature. Comparisons between potato RFLP maps derived from different genetic backgrounds revealed conservation of marker order but differences in chromosome and total map length. In particular, significant reduction of map length was observed in interspecific compared to intraspecific crosses. The distribution of regions with distorted segregation ratios in the genome was analyzed for four potato parents. The most prominent distortion of recombination was found to be caused by the self-incompatibility locus.

Differential effect of L-threo-3,4-dihydroxyphenylserine in pure autonomic failure and multiple system atrophy with autonomic failure

Treatment with L-threo-3,4-dihydroxyphenylserine (L-threo-dops), a synthetic precursor of norepinephrine, significantly increased upright blood pressure in patients with multiple system atrophy but had no effect on the upright blood pressure of patients with pure autonomic failure. These results suggest that the site of action of L-threo-dops is central and that its pressor effect requires intact peripheral sympathetic neurons.

Sequence variability and gene structure at the self-incompatibility locus of Solanum tuberosum

Allelic complexity is a key feature of self-incompatibility (S) loci in gametophytic plants. We describe in this report the allelic diversity and gene structure of the S locus in Solanum tuberosum revealed by the isolation and characterization of genomic and cDNA clones encoding S-associated major pistil proteins from three alleles (S1, Sr1, S2). Genomic clones encoding the S1 and S2 proteins provide evidence for a simple gene structure: Two exons are separated by a small intron of 113 (S1) and 117 bp (S2). Protein sequences deduced from cDNA clones encoding S1 and Sr1 proteins show 95% homology, 15 of the 25 residues that differ between these S1 and Sr1 alleles are clustered in a short hypervariable protein segment (amino acid positions 44-68), which corresponds in the genomic clones to DNA sequences flanking the single intron. In contrast, these alleles are only 66% homologous to the S2 allele, with the residues that differ between the alleles being scattered throughout the sequence. DNA crosshybridization experiments identify a minimum of three classes of potato S alleles: one class contains the alleles S1, Sr1 and S3, the second class S2 and an allele of the cultivar Roxy, and the third class contains at present only S4. It is proposed that these classes reflect the origin of the S alleles from a few ancestral S sequence types.