Bladder outlet obstruction by a lymphocele following kidney transplantation

Lymphocele is a well-known complication of kidney transplantation. Patients usually present with deteriorating renal function, hydronephrosis, a nontender lower abdominal mass or ipsilateral leg edema. Urinary retention, however, is an unusual presentation of lymphocele. We herein report a case of a female patient who developed chronic urinary retention due to a pelvic lymphocele after kidney transplantation.

Prognostic significance of DNA replication errors in young patients with colorectal cancer

OBJECTIVE

To determine the DNA replication error (RER) status in young patients with colorectal cancer (CRC), and to compare the clinical and pathologic characteristics of RER-positive and RER-negative cases.

SUMMARY BACKGROUND DATA

Recent studies suggest that patients with RER-positive CRC have an improved prognosis. Further data are required to confirm this observation in young CRC patients.

METHODS

All patients 40 years of age and younger with CRC admitted to the National Naval Medical Center between 1970 and 1992 were considered for inclusion in the study. After review, 36 patients for whom the original archived pathology specimen could be retrieved served as the study population. The RER status was determined using a previously described polymerase chain reaction-based assay. The clinical and pathologic features and survival data were compared to RER status.

RESULTS

RER-positive tumors were found in 17 cases (47%). There was no significant difference in Dukes' stage or histologic grade at the time of diagnosis between patients with RER-positive tumors compared to RER-negative tumors. Patients with RER-positive tumors were found to have an improved prognosis: the 5-year survival probability for patients with RER-positive tumors was 68%, as compared to 32% for patients with RER-negative tumors (p < 0.05).

CONCLUSIONS

RER-positive tumors are common in young patients with CRC, and patients with RER-positive tumors have a significantly improved prognosis. Because of their young age, survival data and prognosis play an important role in the overall treatment plan of young patients with CRC. Therefore, knowledge of RER status could affect initial therapy, postoperative chemotherapy, and follow-up.

Phrenic nerve injury after coronary artery bypass grafting: will it go away?

BACKGROUND

Phrenic nerve injury after coronary artery bypass grafting resolves in most cases. The purpose of this study was to analyze the causes and effects of persistent phrenic nerve injury after coronary artery bypass grafting.

METHODS

From a registry of patients with chronic obstructive pulmonary disease who underwent coronary artery bypass grafting, 64 patients were identified who experienced phrenic nerve injury during their operation. Fifteen patients either died during follow-up (n = 9) or were lost to follow-up (n = 6). At the last follow-up visit, all the patients underwent an ultrasound evaluation of the diaphragm and were divided into those who had persistent dysfunction (group I) and those who had normal function (group II). The groups were compared for preoperative and operative risk factors, acute and midterm postoperative results, and quality of life at last follow-up.

RESULTS

There were 13 patients in group I and 36 in group II. There were no significant differences in preoperative and operative risk factors between the groups. The length of hospitalization was similar for both groups (9.2 +/- 4.5 versus 8.5 +/- 3.3 days, respectively; p = 0.77). More patients in group I required reintubation (23% versus 14%, respectively; p = 0.04). The mean duration of follow-up was 32.7 +/- 9.2 months. At that time, both groups suffered a reduction of forced expiratory volume in 1 second compared with preoperative values. Group I had a greater reduction in forced expiratory volume in 1 second (p = 0.05). There were a total of 125 postoperative readmissions during the follow-up period, 36 in group I and 89 in group II. There were more admissions because of pulmonary problems in group I (85% versus 53%; p = 0.04). Of the 49 patients, 21 perceived a decline in quality of life after operation. More patients in group I (46% versus 22%; p = 0.05) complained of this decrease.

CONCLUSIONS

A significant number of patients who incur phrenic nerve injury after coronary artery bypass grafting have persistent phrenic nerve injury. Patients with persistent phrenic nerve injury have increased acute and midterm morbidity after operation, as well as reduced quality of life.

Abdominal compartment syndrome due to delayed identification of a ureteral perforation following abdomino-perineal resection for rectal carcinoma

Abdominal compartment syndrome develops whenever the mean intraperitoneal pressure rises above the physiological pressure, leading to renal and mesenteric ischemia and respiratory decompensation due to pressure on the diaphragm. Abdominal compartment syndrome may occur after conditions such as peritonitis, intestinal obstruction, laparoscopic procedures, or abdominal tumors. Leakage from the urinary tract may cause accumulation of urine in the peritoneal cavity which commonly manifests as single or multiple urinomas, or urinary ascites. The case of a patient who had delayed identification of a ureteral perforation following the abdomino-perineal resection of a rectal carcinoma is presented. Massive urinary leakage into the peritoneal cavity led to the abdominal compartment syndrome. Peritoneal drainage and ureteral stenting improved her condition. A high index of suspicion is necessary in order to diagnose this rare condition.

Deficits in gray matter volume are present in schizophrenia but not bipolar disorder

Studies using magnetic resonance (MR) imaging have provided strong evidence that patients with schizophrenia as a group have structural brain abnormalities, including enlarged ventricles and sulci as well as smaller cortical gray matter volumes. This study was undertaken to investigate whether the brain abnormalities found in schizophrenia could be distinguished from those seen in bipolar disorder. The MR scans of 23 patients with schizophrenia were compared to those of 17 healthy community volunteers and 14 patients with bipolar disorder. Images were processed using computer-based image processing techniques to generate quantitative measures of cerebrospinal fluid (CSF), gray matter and white matter volumes. Compared to the community volunteers, the schizophrenia group had larger total CSF volumes while the bipolar group had larger ventricles. Smaller cortical gray matter volumes were found in the schizophrenia group, but not in the bipolar group. The schizophrenia group had regional deficits in gray matter volumes in comparison with both the community volunteers and the bipolar group. These findings suggest that the brain tissue abnormalities found in schizophrenia and bipolar disorder may be distinguishable using MR imaging.

[Radical retropubic prostatectomy]

Radical prostatectomy may cure most patients in whom the malignant tumor has not invaded through the prostatic capsule. Advances in surgical technique and accumulation of experience have decreased the complication rate significantly. Long-term results of surgical treatment are now better than those of other forms of treatment; hence radical prostatectomy is now recommended for men with life expectancies longer than 10 years. Between 1988 and 1995, 164 men with clinical stages T1 or T2 adenocarcinoma were admitted for radical prostatectomy. Most were not offered a nerve-sparing procedure, so as to allow wider, more complete resection. Those who wanted preservation of sexual function underwent the nerve- preserving procedure. In 6 patients operation was discontinued when metastases to the mac lymph nodes were detected and in 1 when invasion of the pelvic wall was found, 157 underwent radical prostatectomy. Preoperative biopsy revealed a low-grade lesion (Gleason 2-4) in 19.1%, intermediate grade (Gleason 5-6) in 61.8% and high-grade (Gleason 7-9) in 19.1%; however, pathologic grading revealed that only 7.0% had grade 2-4 tumor, 60.5% grade 5-6 and 32.5% grade 7-9. Pathologic staging revealed T2 tumor in 58%, T3 in 38.8% (including microscopic invasion of the capsule or seminal vesicles); microscopic lymph node metastases were found in 3.2%. Tumor invasion through the capsule was found in only 2 of 13 treated with neoadjuvant androgen blockade, compared with 40% in those who did not receive this treatment. There was no operative mortality and only 14.7% has complications. All had urinary incontinence immediately after operation, but regained continence after an average of 4-5 months, 24 were incontinent for more than 12 months, but most of them had only mild stress incontinence. Most patients were impotent after the procedure. There was tumor recurrence, diagnosed by rise in serum PSA, in 26 during an average followup of 26.4 months (range 3-93). Cure rate of prostatic cancer by radical prostatectomy may be increased by improved preoperative staging methods and better patient selection; long term follow up is required for determining cure rate.

Phrenic nerve injury after coronary artery grafting: is it always benign?

BACKGROUND

The purpose of this study was to evaluate the effect of phrenic nerve injury (PNI) occurring during coronary artery bypass grafting in patients with major chronic obstructive pulmonary disease (COPD).

METHODS

Over a 42-month period, 1,303 patients underwent primary coronary artery bypass grafting. Sixty-seven (5.14%) had major COPD, and 29 (43.3%) of these 67 sustained PNI (group I). These patients were matched for age and ejection fraction with 29 CABG patients with COPD but without PNI (group II), 29 patients without COPD but with PNI (group III), and 29 patients with neither COPD nor PNI (group IV). The groups were compared on the basis of preoperative and operative factors and immediate and midterm morbidity and mortality.

RESULTS

There were no significant differences between the groups with respect to hypertension, diabetes, ejection fraction, number of grafts, internal mammary artery use, cardiopulmonary bypass time, and ischemic time. Postoperatively, group I had a longer total hospitalization (group I, 11.7 days; group II, 7.8 days; group III, 7.8 days; and group IV, 6 days; p = 0.0001) and stay in the intensive care unit (I, 3.6 days; II, 2.2 days; III, 2.1 days; and IV, 1.2 days; p = 0.0023). More patients in group I required reintubation (I, 37.9%; II, 3.4%; III, 6.9%; and IV, 0%; p < 0.0001). Mean follow-up was 32.8 months (range, 7 to 48 months). Group I had more hospital readmissions (I, 78; II, 50; III, 61; and IV, 28; p < 0.007) and lower cumulative survival (I, 60.6%; II, 93%; III, 96.8%; and IV, 100%; p < 0.0015) compared with the other groups.

CONCLUSIONS

In patients with COPD, PNI during coronary artery bypass grafting has a major negative impact on immediate and midterm results.

[Superficial dorsal penile vein thrombosis (Mondor's disease)]

Superficial venous thrombosis of the chest wall was first described by Mondor in 1939. Braun-Falco reported in 1955 superficial penile vein involvement in diffuse thrombophlebitis of the abdominal wall and in 1958 Helm and Hodge first described isolated superficial dorsal penile vein thrombosis. Since then, fewer than 50 cases have been reported. The clinical presentation is usually redness and swelling of the dorsum of the penis, accompanied by a palpable, tender thrombotic vein. This acute and painful disease frightens the patients, who is concerned about his fertility and sexual function. The main cause of this disease is frequent sexual intercourse. Diagnosis is based upon anamnesis, physical examination and penile sonography with color Doppler imaging. It is usually a benign disease which resolves quickly under appropriate medical therapy. We present a man who was admitted for this condition and was successfully treated.

Recurrent inhibition between motor nuclei innervating opposing wrist muscles in the human upper limb

1. Effects of conditioning motor volleys of increasing amplitude on antagonistic motor nuclei were tested at the wrist and elbow level in man. 2. The modifications of biceps, triceps, flexor carpi radialis (FCR) and extensor carpi radialis (ECR) motoneurone excitability were tested both in post-stimulus time histogram (PSTH) and rectified averaged EMG experiments. 3. Conditioning motor volleys were evoked in biceps, triceps, FCR and ECR muscles by electrical stimuli applied to the corresponding nerves. The intensity of the conditioning stimuli was systematically varied from an intensity just below motor threshold to one giving rise to a motor response equal to half of the maximal direct motor response (Mmax). 4. The effect of the injection of a cholinergist agonist, L-acetylcarnitine (L-Ac), on antagonistic conditioning motor volleys was tested for each motor nucleus. 5. Results obtained at the wrist and elbow level were strikingly different. Antagonistic motor volleys resulted in an early and long-lasting inhibition enhanced by L-Ac injection in wrist motor nuclei, while no modification was observed in elbow motor nuclei. 6. The characteristics of the early and long-lasting inhibition evoked in wrist motor nuclei by antagonistic motor volleys suggest that they are due to the activation of Renshaw cells by the conditioning motor volleys. 7. It is therefore concluded that these experiments provide further evidence that the interconnections between motoneurones, interneurones mediating reciprocal inhibition and Renshaw cells at the wrist level are different from those described elsewhere. Indeed, it has already been shown that the interneurones mediating reciprocal inhibition between FCR and ECR are not inhibited by Renshaw cells, and the results presented here suggest that FCR-coupled Renshaw cells inhibit ECR motoneurones and vice versa.

Life-threatening retroperitoneal hematoma caused by anticoagulant therapy for myocardial infarction after SWL

Extracorporeal shock wave lithotripsy, the primary treatment for renal and ureteral stones, is an elective procedure with a low rate of complications, although most patients have macrohematuria which lasts for a few hours, and as many as 25% develop a renal or perirenal hematoma. Therefore, SWL is not performed during anticoagulant therapy, and any blood dyscrasias should be corrected prior to the procedure. We present a case of a patient who had an acute myocardial infarction after SWL, was treated with anticoagulation and emergency coronary angioplasty, and subsequently developed a life-threatening retroperitoneal hemorrhage. Cessation of anticoagulation with fluid support and drainage of a pleural effusion eventually resulted in complete recovery.

Assessment of a new self-rating scale for post-traumatic stress disorder

BACKGROUND

In post-traumatic stress disorder (PTSD) there is a need for self-rating scales that are sensitive to treatment effects and have been tested in a broad range of trauma survivors. Separate measures of frequency and severity may also provide an advantage.

METHODS

Three hundred and fifty-three men and women completed the Davidson Trauma Scale (DTS), a 17-item scale measuring each DSM-IV symptom of PTSD on 5-point frequency and severity scales. These subjects comprised war veterans, survivors of rape or hurricane and a mixed trauma group participating in a clinical trial. Other scales were included as validity checks as follows: Global ratings, SCL-90-R, Eysenck Scale, Impact of Event Scale and Structured Clinical Interview for DSM-III-R.

RESULTS

The scale demonstrated good test-retest reliability (r = 0.86), internal consistency (r = 0.99). One main factor emerged for severity and a smaller one for intrusion. In PTSD diagnosed subjects, and the factor structure more closely resembled the traditional grouping of symptoms. Concurrent validity was obtained against the SCID, with a diagnostic accuracy of 83% at a DTS score of 40. Good convergent and divergent validity was obtained. The DTS showed predictive validity against response to treatment, as well as being sensitive to treatment effects.

CONCLUSIONS

The DTS showed good reliability and validity, and offers promised as a scale which is particularly suited to assessing symptom severity, treatment outcome and in screening for the likely diagnosis of PTSD.

Assessment of a new self-rating scale for post-traumatic stress disorder

BACKGROUND

In post-traumatic stress disorder (PTSD) there is a need for self-rating scales that are sensitive to treatment effects and have been tested in a broad range of trauma survivors. Separate measures of frequency and severity may also provide an advantage.

METHODS

Three hundred and fifty-three men and women completed the Davidson Trauma Scale (DTS), a 17-item scale measuring each DSM-IV symptom of PTSD on 5-point frequency and severity scales. These subjects comprised war veterans, survivors of rape or hurricane and a mixed trauma group participating in a clinical trial. Other scales were included as validity checks as follows: Global ratings, SCL-90-R, Eysenck Scale, Impact of Event Scale and Structured Clinical Interview for DSM-III-R.

RESULTS

The scale demonstrated good test-retest reliability (r = 0.86), internal consistency (r = 0.99). One main factor emerged for severity and a smaller one for intrusion. In PTSD diagnosed subjects, and the factor structure more closely resembled the traditional grouping of symptoms. Concurrent validity was obtained against the SCID, with a diagnostic accuracy of 83% at a DTS score of 40. Good convergent and divergent validity was obtained. The DTS showed predictive validity against response to treatment, as well as being sensitive to treatment effects.

CONCLUSIONS

The DTS showed good reliability and validity, and offers promised as a scale which is particularly suited to assessing symptom severity, treatment outcome and in screening for the likely diagnosis of PTSD.

Branchial pouch sinus tract from the piriform fossa causing acute suppurative thyroiditis, neck abscess, or both: CT appearance and the use of air as a contrast agent

OBJECTIVE

Our objective was to describe the CT appearance of acute suppurative thyroiditis and neck abscess associated with a congenital sinus tract arising from the piriform fossa. In addition, we describe our observations on the use of air as a contrast agent during CT of the pharynx.

CONCLUSION

The thyroid is extremely resistant to acute bacterial infection; hence, when such an infection does occur, an underlying anomaly of the thyroid should be suspected, particularly when the infection is recurrent. In such a case, sonography or CT must be used to confirm the diagnosis of acute thyroiditis, neck abscess, or both. Then the sinus tract must be revealed by barium esophagography, CT scanning that use air as a contrast agent, or endoscopy.

Intraoperative maintenance of tissue perfusion prevents ARDS. Adult Respiratory Distress Syndrome

Patients undergoing prolonged, complex oncological surgery are at increased risk of developing the adult respiratory distress syndrome (ARDS) and other organ failures. Our hypothesis is that maintaining adequate tissue perfusion and oxygenation may prevent tissue hypoxia and acidosis in pulmonary, peripheral, and splanchnic microcirculations. Experimental evidence suggests that the hypoxic, acidotic endothelium stimulates the release of cytokines, kinins, and other mediators. We developed and tested an intraoperative protocol for surgical patients likely to develop ARDS and organ dysfunction; the protocol focuses on the intraoperative period but is not limited to this time. Nitroglycerin and fluids were used to maintain tissue perfusion and prevent tissue hypoxia as reflected by transcutaneous oxygen tension values. In 155 high-risk patients, none developed ARDS. We conclude that maintenance of tissue perfusion and oxygenation in high-risk surgical patients decreases the incidence of ARDS.

Detection of hepatocellular carcinoma in cirrhotic patients: sensitivity of CT and ultrasonography

Patients with cirrhosis are at increased risk for the development of hepatocellular carcinoma. The heterogeneous hepatic parenchyma produced by cirrhosis makes detection of hepatomas more difficult. The purpose of this study was to determine the sensitivities of CT and ultrasonography for detecting hepatomas in cirrhotic patients. A retrospective analysis was performed of 733 patients who underwent liver transplantation at our institution. A study population of 21 patients was selected who met our inclusion criteria. The inclusion criteria required a pathologic diagnosis of hepatocellular carcinoma, pathologic evidence of cirrhosis, and contrast-enhanced CT and sonographic examinations performed within 1 week of each other. The sensitivities of CT and ultrasonography were determined by comparing the imaging findings with pathology findings from serially sectioned total hepatectomy specimens. A total of 40 hepatomas were detected pathologically in the 21 patients in our study population. CT identified 12 of 21 patients with hepatomas and detected 18 of 40 individual lesions (patient detection sensitivity = 57%, lesion detection sensitivity = 45%). Ultrasonography identified 14 of 21 patients with hepatomas and detected 21 of 40 individual lesions (patient detection sensitivity = 67%, lesion detection sensitivity = 51%). Combining the findings of CT and ultrasonography allowed identification of 17 of 21 patients with hepatomas and detection of 24 of 40 individual lesions (patient detection sensitivity = 80%, lesion detection sensitivity = 60%). We conclude that CT and ultrasonography have a low sensitivity for the detection of hepatocellular carcinoma in patients with cirrhosis.

Cutaneous and pulmonary infections caused by Mycobacterium vaccae

Mycobacterium vaccae is a rapidly growing mycobacterial species that was previously not considered a human pathogen. We report four cases of M. vaccae infection that occurred in the southern United States; one patient had cutaneous disease, and three patients had cavitary lung disease. Two of the three patients with pulmonary disease had a history of exposure to cattle. The conditions of all patients improved with therapy: the cutaneous infection responded to therapy with minocycline and trimethoprim-sulfamethoxazole, and the pulmonary infections responded to therapy with ciprofloxacin.

Effects of track structure and cell inactivation on the calculation of heavy ion mutation rates in mammalian cells

It has long been suggested that inactivation severely effects the probability of mutation by heavy ions in mammalian cells. Heavy ions have observed cross sections of inactivation that approach and sometimes exceed the geometric size of the cell nucleus in mammalian cells. In the track structure model of Katz the inactivation cross section is found by summing an inactivation probability over all impact parameters from the ion to the sensitive sites within the cell nucleus. The inactivation probability is evaluated using the dose-response of the system to gamma-rays and the radial dose of the ions and may be equal to unity at small impact parameters for some ions. We show how the effects of inactivation may be taken into account in the evaluation of the mutation cross sections from heavy ions in the track structure model through correlation of sites for gene mutation and cell inactivation. The model is fit to available data for HPRT mutations in Chinese hamster cells and good agreement is found. The resulting calculations qualitatively show that mutation cross sections for heavy ions display minima at velocities where inactivation cross sections display maxima. Also, calculations show the high probability of mutation by relativistic heavy ions due to the radial extension of ions track from delta-rays in agreement with the microlesion concept. The effects of inactivation on mutations rates make it very unlikely that a single parameter such as LET or Z*2/beta(2) can be used to specify radiation quality for heavy ion bombardment.

CT of submandibular gland sialolithiasis

We emphasise the importance of high-resolution CT with reconstruction in the demonstration of submandibular gland (SMG) sialolithiasis and its role in monitoring treatment. We studied 76 patients with swollen and tender SMG, some with fever. They underwent conventional radiography, sonography (US) and high-resolution CT with reconstructions. Conventional radiographs demonstrated single stones in 29 patients. Axial CT, before reconstructions, demonstrated single stones in 63 patients and multiple stones in another 5. Following CT reconstructions, multiple stones were demonstrated in 37 patients. On US stones were diagnosed in only 33 patients, and multiple stones in only 1. All 68 patients with stones shown on imaging and 2 without stones underwent surgery, with good clinical results. Total removal of the SMG and its duct was performed in patients with multiple stones, chronic inflammatory changes in the SMG, or a solitary stone in the SMG or deep in the duct. A small incision for removal of a solitary stone in the distal aspect of Wharton's duct was performed in 15 patients, with excellent clinical results. Another 14 patients with multiple salivary gland stones, diagnosed on CT reconstructions, did not improve following this procedure and needed further surgery; clinical improvement occurred following excision of the SMG and Wharton's duct. Histological examination in all of these confirmed the presence of additional stones. Conservative anti-inflammatory treatment was recommended for 6 patients in whom CT reconstructions did not demonstrate stones.

Appendiceal colic in children: a true clinical entity?

BACKGROUND

Unexplained recurrent abdominal pain is a frequent problem in the pediatric population. An organic cause is found in 10 percent of children. Recurrent abdominal pain is responsible for multiple hospital admissions and patient evaluations. In some children, partial luminal obstruction of the appendix without inflammation may be the cause of this pain, and is defined as "appendiceal colic."

STUDY DESIGN

During a period of five years, we performed a prospective study among children admitted for right lower quadrant abdominal pain. Children operated on for suspected acute appendicitis were eliminated from the study. Among the remaining patients, those with recurrent pain were evaluated for appendiceal colic. Medical histories were obtained, and the patients underwent physical examinations, routine laboratory studies, stool cultures, abdominal roentgenograms, and sonography scans (including the pelvic region in girls). Precise radiologic evaluation of the appendix was performed by barium swallow in 22 children or by barium enema in four. The diagnosis of appendiceal colic was made if the following three criteria were met: a history of longer than one month with three or more recurrent attacks of right lower quadrant abdominal pain; localized tenderness in the right lower abdomen without signs of peritoneal irritation or inflammation; or radiologic findings at barium examination consisting of irregular filling of the appendix, nonfilling or partial filling of the appendix after 24 hours, or nonemptying of the appendix after 72 hours. Children thus diagnosed underwent elective appendectomy, which was performed only after an additional episode of abdominal pain.

RESULTS

Twenty-six children (average age 11.4 years) were treated by appendectomy and of these, 23 (88.5 percent) experienced pain relief in the immediate postoperative period. The remaining three children had pain relief within four months after appendectomy.

CONCLUSIONS

Appendiceal colic may be a true clinical entity. Children suffering from appendiceal colic may benefit from elective appendectomy.

The hormonal response to intravenous 5-hydroxytryptophan in bulimia nervosa

In recent years evidence has accumulated to implicate a disturbance in serotonin function in the eating disorder bulimia nervosa. This study employs a neuroendocrine technique to assess the effect of intravenous 5-hydroxytryptophan, the immediate precursor to serotonin, on peripheral hormones in bulimia nervosa subjects and controls. Blunted prolactin and growth hormone responses were observed among bulimia nervosa subjects; the possible pathophysiology and implications of the findings are discussed.

The calculation of radial dose from heavy ions: predictions of biological action cross sections

The track structure model of heavy ion cross sections was developed by Katz and co-workers in the 1960s. In this model the action cross section is evaluated by mapping the dose-response of a detector to gamma rays (modeled from biological target theory) onto the radial dose distribution from delta rays about the path of the ion. This is taken to yield the radial distribution of probability for a "hit" (an interaction leading to an observable end-point). Radial integration of the probability yields the cross section. When different response from ions of different Z having the same stopping power is observed this model may be indicated. Since the 1960s there have been several developments in the computation of the radial dose distribution, in the measurement of these distributions, and in new radiobiological data against which to test the model. The earliest model, by Butts and Katz made use of simplified delta ray distribution functions, of simplified electron range-energy relations, and neglected angular distributions. Nevertheless it made possible the calculation of cross sections for the inactivation of enzymes and viruses, and allowed extension to tracks in nuclear emulsions and other detectors and to biological cells. It set the pattern for models of observable effects in the matter through which the ion passed. Here we outline subsequent calculations of radial dose which make use of improved knowledge of the electron emission spectrum, the electron range-energy relation, the angular distribution, and some considerations of molecular excitation, of particular interest both close to the path of the ion and the outer limits of electron penetration. These are applied to the modeling of action cross sections for the inactivation of several strains of E-coli and B. subtilis spores where extensive measurements in the "thin-down" region have been made with heavy ion beams. Such calculations serve to test the radial dose calculations at the outer limit of electron penetration. We lack data from which to test these calculations in regions close to the path of the ion aside from our earliest work on latent tracks in plastics, though it appears that the criterion then suggested for the threshold of track formation, of a minimal dose at a minimal distance (of about 20 angstroms, in plastics), remains valid.

A hospital-based twin register of the heritability of DSM-IV unipolar depression

OBJECTIVES

To estimate the contribution of genes and shared family environment to the liability to DSM-IV major depression and to examine the influence of certain proband characteristics on twin concordance.

METHODS

We studied 177 probands with major depressive disorder ascertained via the Maudsley Hospital Twin Register (London, England) and their same-sex co-twins. Diagnostic assessments were carried out blind to zygosity and information on the other member of the twin pair. Probandwise concordances were used to compute correlations in liability, and model fitting was performed using maximum likelihood procedures.

RESULTS

The probandwise concordance was 46% in monozygotic (n = 68) and 20% in dizygotic (n = 109) twins, a statistically highly significant difference. There was no evidence of a sex difference in heritability or of shared environmental effects. Depending on the assumed population risks for DSM-IV, major depression estimates of heritability were between 48% and 75%. A duration of longest episode of less than 13 months, multiple episodes, and an endogenous rather than neurotic pattern of symptoms as established by the International Classification of Diseases, Ninth Revision, in the proband were associated with a trend toward a higher monozygotic-dizygotic concordance ratio. Using log-linear analysis, only the association between duration of episodes and monozygotic-dizygotic concordance ratio was significant.

CONCLUSIONS

Liability to DSM-IV major depression has a substantial heritable component, and there is no evidence of an effect of shared family environment. Some proband characteristics, especially shorter duration of episodes, may be associated with a larger degree of genetic determination.