Dominant genes for colorectal cancer are not rare

The genetic basis for colorectal cancer was investigated by complex segregation analysis of a published series of consecutive pedigrees ascertained through patients undergoing treatment for colorectal cancer. Analysis favoured a dominant gene or genes with a frequency of 0.006 with a lifetime penetrance of 0.63. These genes account for 81% of colorectal cancer in patients under 35, however, by 65 about 85% are phenocopies.

Perceptions of infertility and treatment stress in females as compared with males entering in vitro fertilization treatment

OBJECTIVE

To determine gender similarities and differences in perceptions of infertility and anticipated treatment stress in couples enrolling for in vitro fertilization (IVF) treatment.

DESIGN

Both partners were evaluated at enrollment of IVF treatment. The evaluation was part of the screening procedure.

SETTING

The Department of Obstetrics and Gynecology at a teaching hospital.

PATIENTS, PARTICIPANTS

Two hundred consecutive couples who entered an IVF treatment program.

MAIN OUTCOME MEASURES

Self-report questionnaire included items on the duration of infertility, degree of social support, effect of infertility on sexual relationship, expected likelihood of achieving pregnancy, anticipation of stress during treatment, and a self-rating scale of emotional reactions to infertility.

RESULTS

The women anticipated more stress in IVF treatment but also rated greater degree of social support than the men. Both partners overestimated their chances of a successful treatment outcome. Factor analysis of the Infertility Scale produced three factors that were similar for both sexes. The first factor represented the desire to have a child as a major focus of life with inadequacy of the male role, social functioning and work efficiency, and pressure to have a child following.

CONCLUSIONS

Women reported more stress, but the factors affecting stress of infertility were very similar for both partners. The intense focus on having a child was the predominant factor in anticipated stress of IVF treatment for both males and females.

Workshop on DNA repair

A workshop on DNA repair with emphasis on eukaryotic systems was held, under the auspices of the EC Concerted Action on DNA Repair and Cancer, at Noordwijkerhout (The Netherlands) 14-19 April 1991. The local organization of the meeting was done under the auspices of the Medical Genetic Centre South-West, The Netherlands (MGC), c/o Department of Radiation Genetics and Chemical Mutagenesis, University of Leiden (The Netherlands). Local organizers were: D. Bootsma (chairman), W. Ferro, J.H.J. Hoeijmakers, A.R. Lehmann, P.H.M. Lohman, L. Mullenders, and A.A. van Zeeland (secretarial assistance: Mrs. C. Escher-van Heerden and Mrs. R. Bontre). Over 190 scientists participated, and the format of the meeting followed that of the 1987 workshop on the 'Molecular Aspects of DNA Repair' (Friedberg et al., 1987). Plenary review talks in the mornings were followed, in the afternoon, by poster viewing in three or four parallel sessions. Groups of 15-20 posters were discussed in detail, and later on, in plenary sessions, chairpersons of the poster discussions reviewed the afternoons' posters. The principal themes of the meeting were the isolation and characterisation of repair genes and proteins, repair in specific sequences, consequences of defective DNA repair, and new methods for detecting DNA damage and repair. Remarkable progress has been made recently in all of these areas, and many exciting new results were presented. It is impossible to summarize all contributions to this (intensive) one-week meeting. Therefore, and for the sake of coherence, presentations that did not fit easily into any of the general themes of the meetings have not been included.

The prevalence, aetiology and clinical significance of pseudo-sinusoidal fetal heart rate patterns in labour

OBJECTIVE

To investigate the prevalence of sinusoidal and pseudo-sinusoidal fetal heart rate (FHR) patterns in labour and the relation between the characteristics of the FHR pattern and fetal outcome.

DESIGN

A prospective observational study over a 6-month period in which all women who had continuous FHR monitoring in labour had their intrapartum cardiotocographs (CTGs) scrutinized for the presence of sinusoidal or pseudo-sinusoidal FHR patterns.

SETTING

John Radcliffe Hospital, Oxford.

SUBJECTS

1520 women who had fetal monitoring during labour for various reasons.

MAIN OUTCOME MEASURES

Both internal (electrocardiographic) and external (ultrasound) recordings of the FHR were analysed. Abnormal FHR patterns were related to obstetric characteristics and fetal outcome in terms of Apgar scores, umbilical artery pH and admission to the special care unit.

RESULTS

No true sinusoidal FHR patterns were observed, but pseudo-sinusoidal FHR patterns were found in 230 of the 1520 CTGs examined (15%). Of these, 219 were classified as minor (amplitude 5-15 beats/min) and 11 as intermediate (amplitude 16-24 beats/min). Major pseudo-sinusoidal FHR patterns (amplitude greater than 24 beats/min) were not observed. Minor pseudo-sinusoidal FHR patterns had a mean duration of 21 (SD 13) min and typically occurred once or twice early in labour. Using logistic regression analysis a significant, independent relation was demonstrated between the presence of minor pseudo-sinusoidal FHR patterns and the use of pethidine (RR 1.84, 95% CI 1.3 to 2.59, P less than 0.0001) and epidural analgesia (RR 1.85, 95% CI 1.24 to 2.76, P less than 0.001). Intermediate pseudo-sinusoidal FHR patterns were found in association with both in utero fetal sucking and transient episodes of fetal hypoxia such as that caused by periodic umbilical cord compression.

CONCLUSION

Pseudo-sinusoidal FHR patterns in labour will usually be associated with a normal fetal outcome but a careful fetal assessment is mandatory.

A variant of glycophorin A resulting from the deletion of exon 4

We have isolated a variant form of glycophorin A which has a 39 bp deletion corresponding to nucleotides 233 to 270 of the coding sequence, which is exon 4 of the glycophorin A gene. The remainder of the sequence is identical to that of the M phenotype of glycophorin A.

Genetic epidemiology of complex phenotypes

A theory is given for complex phenotypes represented by an ordered polychotomy separately for affected (as severity) and for normals (as diathesis), with consideration of history, ascertainment, sampling frames, and phenotype systems. Nonrandom selection of probands by severity is permitted. Both probit and logistic models are developed in a form compatible with segregation and/or linkage analysis. Probabilities are set out in detail in the Appendix. This approach avoids problems that have been encountered with quantitative traits and correlated phenotypes, although using this information.

Genetic epidemiology of ovarian cancer: segregation analysis

The genetic epidemiology of ovarian cancer has been investigated by complex segregation analysis of 462 pedigrees ascertained through a normal consultant. The observed pattern of ovarian cancer is compatible with an autosomal dominant gene. The gene frequency of the abnormal allele is 0.0015-0.0026 with a lifetime penetrance of 0.74-0.79. The gene frequency accounts for a significant proportion of ovarian cancer in young women. By age 70 the majority of affected women are phenocopies. The results from this analysis should enable the risks of ovarian cancer to be more accurately estimated than by empiric methods for relatives of affected women, and can maximize the usefulness of screening programmes and future linkage studies.

Comparative experience with smooth and polyurethane breast implants using the Kaplan-Meier method of survival analysis

Smooth-walled silicone implants have been widely used in breast surgery. Capsular contracture, causing undesirable firmness and spherical deformity, has been a common problem. Recent studies suggest that polyurethane-covered breast implants are associated with a lower incidence of capsular contracture. The statistical methodology employed in some of these studies, however, may be subject to criticism. Between July of 1984 and June of 1990 (72 months), 427 polyurethane breast implants were used in 279 patients and 439 smooth prostheses were used in 250 patients for a variety of aesthetic and reconstructive procedures. The occurrence of capsular contracture was carefully monitored and then analyzed using the Kaplan-Meier method of survival analysis. This method is particularly well suited to analysis of these types of clinical data because it allows for the fact that contractures occur at varying intervals after surgery and that follow-up of patients is incomplete. The probability of capsular contracture with smooth-walled prostheses was found to be significantly greater than with polyurethane-covered implants in each group of patients studied (p less than 0.05). Other complications occurred at a similar rate regardless of prosthesis type. This study supports the belief that polyurethane breast implants have a lower contracture rate; furthermore, it introduces the Kaplan-Meier method for analyzing the outcome of alternative plastic surgical therapies.

Error filtration, interference, and the human linkage map

Typing error is a major problem in constructing human linkage maps, leading to incorrect orders and inflating map lengths. An error filter is incorporated into multiple pairwise analysis that corrects for inflation of map lengths and improves recovery of the correct order. Multipoint mapping is more sensitive to error, but when its output is adjusted for both error and interference, map lengths are no longer inflated in proportion to the number of loci and are close to those obtained by multiple pairwise analysis.

Effects of taipan (Oxyuranus scutellatus) venom on erythrocyte morphology and blood viscosity in a human victim in vivo and in vitro

The case of a snake handler with envenoming due to Australian taipan (Oxyuranus scutellatus) showing marked morphological changes in his red blood cells is presented. The red cells underwent sphero-echinocytic transformation and in subsequent experiments in vitro the effects of taipan venom on red cells were further characterized. Taipan venom induced sphero-echinocytic transformation at nanogram/ml concentrations and led to a marked increase in whole blood viscosity. These changes have not been featured in previous reports of taipan envenomation and are reported to highlight the diagnostic value of blood film examination in cases of suspected envenomation. The significance of the hyperviscosity, and consequent reduction in blood fluidity, is unknown and requires further investigation.

Cardiovascular responses to psychological and physiological stressors during the menstrual cycle

Psychological and physical stress reactivity was studied in 15 females in two phases of the menstrual cycle (cycle days 5-7 and 24-26) and in 15 males. Each female was matched for age and time between sessions with a male. There was a significant phase-related difference in cardiovascular reactivity among the females. Females in the luteal phase reacted significantly more to the cold pressor but not to the mental arithmetic test. There were significant sex differences in systolic blood pressure, the males displaying higher levels during provocation, as well as during control conditions. The females were more reactive in heart rate to the mental stressor when changes from control conditions to stress were calculated. When the data were analyzed separately for smokers and non-smokers, there was a significant interaction between menstrual cycle phase and smoking. In the luteal phase, the female smokers were more reactive in systolic blood pressure than the non-smokers. The male smokers were more reactive than the non-smokers in diastolic blood pressure response to mental arithmetic, but not to the cold pressor test. Significantly higher levels of cortisol and aldosterone were found in the luteal phase as compared with the follicular phase. The cortisol levels were higher in the males than in the females in the follicular phase, whereas the female aldosterone concentrations in the luteal phase were higher than those of the males.

Identification of a peptide inhibitor of the cardiac sarcolemmal Na(+)-Ca2+ exchanger

The deduced amino acid sequence of the cardiac sarcolemmal Na(+)-Ca2+ exchanger has a region which could represent a calmodulin binding site. As calmodulin binding regions of proteins often have an autoinhibitory role, a synthetic peptide with this sequence was tested for functional effects on Na(+)-Ca2+ exchange activity. The peptide inhibits the Na(+)-dependent Ca2+ uptake (KI approximately 1.5 microM) and the Nao(+)-dependent Ca2+ efflux of sarcolemmal vesicles in a noncompetitive manner with respect to both Na+ and Ca2+. The peptide is also a potent inhibitor (KI approximately 0.1 microM) of the Na(+)-Ca2+ exchange current of excised sarcolemmal patches. The binding site for the peptide on the exchanger is on the cytoplasmic surface of the membrane. The exchanger inhibitory peptide binds calmodulin with a moderately high affinity. From the characteristics of the inhibition of the exchange of sarcolemmal vesicles, we deduce that only inside-out sarcolemmal vesicles participate in the usual Na(+)-Ca2+ exchange assay. This contrasts with the common assumption that both inside-out and right-side-out vesicles exhibit exchange activity.

Failure of a knee prosthesis accelerated by shedding of beads from the porous metal surface

A 61-year-old man who received a porous-metal-coated knee implant returned eight months later with chronic synovitis, instability, and loosening of his artificial joint. Subsequently, metal beads were detected in the joint space and soft tissues and were also embedded in the articulating surface of the tibial component. There was scoring of the tibial surface, and polyethylene wear particles were noted in the synovial and fibroconnective-tissue membranes, which had formed beneath the tibial component. Many particles were seen inside giant cells and macrophages. Failure in this case was probably accelerated by the granulomatous response in the soft tissue to wear particles. There was osteolysis rather than new bone growth at the interface with the tibial component. Analysis indicated that poor bead-bonding strength may have initiated the problem. Careful appraisal of the outcome from use of beaded porous-metal-coated devices and assurance of their adequate bonding strength are essential for further progress.

Standard maps of chromosome 10

To achieve consensus more exact definitions of genetical maps are required, of which standard, comprehensive and skeletal might be some. A standard genetic map gives distance from pter in centimorgans (cM), uses the international nomenclature for assigned loci, is sex-specific, and allows as well as possible for interference and typing errors. A standard physical map gives distance from pter in megabases (Mb). A standard map is called comprehensive if it aims to include all syntenic loci, and skeletal if it is limited to loci whose order is well supported. Loci with established order are called skeletal, and are used to define regional assignments of other loci. These principles are illustrated using the CEPH data for chromosome 10. Map lengths by multiple 2-point analysis under supported interference are in good agreement with other evidence, but multipoint mapping gives a substantial overestimate. There are currently 21 loci in the skeletal genetic map and 40 loci in the comprehensive genetic map. From these data, cytogenetic assignments, and partial genetic maps the physical location has been estimated for 85 loci. MEN2A is in a region close to the centromere in which male recombination per megabase is much reduced. Order of DNA markers in this densely mapped region has not been determined, and therefore the exact location of MEN2A is uncertain, although it is likely to lie between D10S34 and D10S30 and close to D10S11.

Counting algorithms for linkage

The Lander-Green algorithm is algebraically different from the EM algorithm that maximizes likelihood. In our experience the numerical difference is very small. Since computations are no easier or convergence faster for the Lander-Green algorithm, there is no reason to prefer it to EM. As suggested by Green (personal communication), layering is advantageous. Occasional updating of the information weights might also be considered to accelerate mapping.

Glucose tolerance in Papua New Guinea: ethnic differences, association with environmental and behavioural factors and the possible emergence of glucose intolerance in a highland community

That Melanesians of non-Austronesian genetic ancestry may be relatively resistant to glucose intolerance was supported by the results of a study of two semitraditional non-Austronesian villages in the Papua New Guinean highlands in 1983, in which an absence of diabetes and a high degree of glucose tolerance and insulin sensitivity were observed. The second of this series of surveys was conducted in 1985 in three non-traditional communities: a periurban, non-Austronesian village in the highlands, and rural and periurban Austronesian villages in coastal locations. Although an absence of diabetes was demonstrated once again in the highlanders, these periurban subjects showed an unexpectedly high insulin response which may be a precursor of glucose intolerance. The notion that highland communities that are living in non-traditional circumstances in Papua New Guinea presently are in "metabolic transition" towards diabetes and other non-communicable diseases, if correct, is of importance to the public health of the nation. In the periurban, coastal-dwelling Austronesians, diabetes with severe hyperglycaemia was demonstrated, and there was some evidence of a secular trend towards increasing glucose intolerance. The two-hour plasma glucose concentrations were shown to be associated with obesity, modernity and Seventh-Day Adventist religious persuasion. However, important and unexplained differences in glucose tolerance remained between rural and periurban coastal dwellers after taking these factors into account.

Family resemblance for glucose tolerance in a Melanesian population, the Tolai

Path analysis of family resemblance for plasma glucose concentration, 2 h after an oral glucose challenge, failed to detect significant genetic heritability. There were no intergenerational differences and marital resemblance was moderate. Over one-third of sibling environmental similarity was due to non-inherited factors. Cultural inheritance was very strong, tending to mimic genetic inheritance, and cultural heritability was considerable. Measures of obesity were included in the environmental index, an estimate of familial environment, in this analysis, for comparability with previous studies. Since obesity appears, in part, to be a heritable trait, in future studies a bivariate approach to family resemblance for both glucose tolerance and obesity could yield important additional insight.

Normal caffeine consumption: influence on thermogenesis and daily energy expenditure in lean and postobese human volunteers

Single-dose oral administration of 100 mg caffeine increased the resting metabolic rate of both lean and postobese human volunteers by 3-4% (p less than 0.02) over 150 min and improved the defective diet-induced thermogenesis observed in the postobese subjects. Measurements of energy expenditure (EE) in a room respirometer indicate that repeated caffeine administration (100 mg) at 2-h intervals over a 12-h day period increased the EE of both subject groups by 8-11% (p less than 0.01) during that period but had no influence on the subsequent 12-h night EE. The net effect was a significant increase (p less than 0.02) in daily EE of 150 kcal in the lean volunteers and 79 kcal in the postobese subjects. Caffeine at commonly consumed doses can have a significant influence on energy balance and may promote thermogenesis in the treatment of obesity.

Volunteer blood donors who fail the copper sulfate screening test. What does failure mean, and what should be done?

Volunteers attending blood donor sessions who fail the copper sulfate screening test merit an explanation of why they are considered ineligible to donate. During a 30-month period, 0.24 percent of men and 2.8 percent of women attending blood donor sessions in the northern region of England failed this test. Their hematologic status was determined by performing complete blood counts on a venous blood specimen and measuring ferritin as an indication of iron stores in a representative sample of approximately 10 percent. Normal blood counts were found in some donors, while others had severe degrees of anemia, and such discrepancies could be clarified only by hemoglobin determinations. Iron deficiency was very common in deferred donors, including 36 of the 88 with normal blood counts in whom ferritin assays were performed. Microcytic blood cells, a hallmark of iron deficiency, were found to be a relatively insensitive measure of low iron stores, except at low levels of hemoglobin. By a check of a venous sample, the hematologic status of most volunteers failing the copper sulfate screening test can be ascertained, and appropriate review, investigation, and treatment can be undertaken.

Hydroxyurea: effects on deoxyribonucleotide pool sizes correlated with effects on DNA repair in mammalian cells

We have measured deoxyribonucleotide pool sizes in different cell types: normal human, transformed human (HeLa), and the permanent hamster line CHO-K1. The range of sizes of the four DNA precursor pools in CHO cells is far greater than in human cells. It is a general rule that hydroxyurea causes rapid depletion of pools (except for dTTP) until the pool present in smallest amount is exhausted; this suggests a tight coupling of the pools to DNA replication (the presumed main cause of the depletion). The effect of hydroxyurea on DNA repair after ultraviolet irradiation (namely, a relatively small accumulation of incomplete repair sites blocked at the resynthesis stage) is probably accounted for by the reduced availability of DNA precursors. However, depletion of the dCTP pool is not an adequate explanation for the observed enhancement by hydroxyurea of the inhibitory effect of cytosine arabinoside; we suggest other possible modes of action. Ultraviolet irradiation has only small effects on the levels of deoxyribonucleotides.

Exploring environments by hand or foot: time-based heuristics for encoding distance in movement space

In Experiment 1, blindfolded observers judged (a) the distance of pathways felt by hand and (b) the straight-line distance between pathway endpoints inferred from such exploration. In Experiment 2, blindfolded observers made corresponding estimates after traversing similar pathways on foot. Pathways were explored under three different speeds. Under both manipulatory and ambulatory exploration, there was substantial length distortion of inferred distance: The straight-line distance was increasingly overestimated with increases in the length of the explored pathway. With manipulatory exploration, slower movements increased length distortion, but duration effects proved secondary to effects of spatial extent. For ambulatory exploration, no duration effects were obtained. Observers used time-independent heuristics, that is, a footstep metric for estimating the pathway actually travelled and a spatial imaging strategy for estimating the inferred line between pathway endpoints. The studies establish length distortion as a general phenomenon in movement space and identify its major causes as spatial rather than temporal.

Cellular responses to ionizing radiation: effects of interrupting DNA repair with chemical agents

This review is concerned with the influence of different classes of chemical agents on cellular repair of DNA damage induced by ionizing radiation. Single-strand break rejoining is little affected by inhibitors of DNA synthesis; however, such inhibitors do lead to a persistence of double-strand breaks in the DNA, and this correlates with an enhancement of chromosome aberrations and cell killing. Experiments with antagonists of topoisomerase II suggest an intriguing role for this DNA unwinding enzyme in double-strand break repair. Interference with poly(ADP-ribose) synthesis, by means of the inhibitor 3-aminobenzamide, does not have a clear-cut effect on recovery from ionizing radiation damage. Various substances (for example, caffeine and trypsin) affect DNA repair via a modulation of the cell cycle, altering the time available to the cell for repairing potentially lethal DNA damage before such damage is 'fixed' by the process of DNA replication. Finally, disturbing cellular energy metabolism, and depressing the level of ATP, can inhibit the repair of radiation damage.

Necrotizing lymphocytic folliculitis: the early lesion of acne necrotica (varioliformis)

Skin biopsy specimens from four patients who had recurrent bouts of lesions conforming to the clinical description of acne necrotica were studied. The pathologic findings were dominated by lymphocytic inflammation around centrally placed follicles evolving to follicular necrosis that extended to the perifollicular epidermis and dermis. Early lesions showed the development of multiple individual necrotic keratinocytes within the follicular sheath and adjacent epidermis with lymphocytic exocytosis. Later lesions showed more intense necrosis and scale crust obscuring the central target but were still dominated by a peripheral lymphocytic infiltrate. The early pathologic findings of acne necrotica (varioliformis) are represented by a necrotizing lymphocytic folliculitis and differ from the pattern seen in association with nonspecific excoriations, acute bacterial folliculitis, classic comedogenic acne, or acnitis.

Estimates of the rate of ligation during excision repair of ultraviolet-damaged DNA in mammalian cells

When ultraviolet-irradiated mammalian cells are incubated with inhibitors of repair DNA synthesis, incomplete repair sites--seen as DNA breaks--accumulate. If the inhibition is reversed, the breaks are joined. Thus the ligation step of excision repair can be investigated. With aphidicolin as inhibitor, ligation occurs at up to 15-times the rate of incision. 3-Aminobenzamide (which inhibits poly(ADPribose) synthesis) does not delay the rejoining of DNA breaks.

DNA repair mutants in higher eukaryotes

Over the past ten years or so, we have seen a proliferation of reports of new cell lines of various vertebrate species, showing hypersensitivity to killing by DNA damaging agents. Regrettably, but predictably, there is no standard terminology to describe the mutants, and as a result the literature is liberally scattered with fragments of individualistic nomenclature. There is no way of imposing order at this stage, but it may be helpful to bring together in this chapter as much information as possible on the mutants now available. As well as being an aid for reference, this should serve as a pointer towards further investigation--either in characterizing the mutants we have, or in developing new ones to fill gaps in our knowledge.

Platelet serotonin uptake and effects of vitamin B6-treatment in premenstrual tension

The platelet serotonin uptake kinetics was studied in 19 women with premenstrual tension syndrome (PMS) and 19 age-matched symptom-free controls during the pre- and postmenstrual phases. Both groups exhibited stable Vmax and Km values at the two phases of the menstrual cycle. There were no differences between the two groups regarding the level of Vmax and Km, respectively. The effect of season (p less than 0.001), with lowered values of Vmax during spring compared to corresponding values during the later half of the year, was identical in both groups. A tendency to lowered Vmax values in the follicular phase in women with PMS during spring may indicate that women with PMS are more vulnerable to developing depressive episodes during this period than symptom-free women. The blood platelet count in whole blood was decreased in the luteal phase in the control group but remained stable in the PMS group. The effect of vitamin B6 on clinical symptoms and the platelet serotonin uptake during the luteal phase was investigated in a double-blind crossover design. Vitamin B6 treatment did not significantly improve the PMS symptoms. There was no effect of treatment on Km. Vmax increased significantly in response to treatment (F = 9.6; p less than 0.001) in both groups, but there was no significant difference between placebo and vitamin B6.

Exploring environments by hand or foot: Time-based heuristics for encoding distance in movement space

In Experiment 1, blindfolded observers judged (a) the distance of pathways felt by hand and (b) the straight-line distance between pathway endpoints inferred from such exploration. In Experiment 2, blindfolded observers made corresponding estimates after traversing similar pathways on foot. Pathways were explored under three different speeds. Under both manipulatory and ambulatory exploration, there was substantial length distortion of inferred distance: The straight-line distance was increasingly overestimated with increases in the length of the explored pathway. With manipulatory exploration, slower movements increased length distortion, but duration effects proved secondary to effects of spatial extent. For ambulatory exploration, no duration effects were obtained. Observers used time-independent heuristics, that is, a footstep metric for estimating the pathway actually travelled and a spatial imaging strategy for estimating the inferred line between pathway endpoints. The studies establish length distortion as a general phenomenon in movement space and identify its major causes as spatial rather than temporal.

Probing for the human coronavirus OC43 in multiple sclerosis

Tissues acquired at autopsy from four patients with MS and biopsies from one patient with a probable diagnosis of MS were probed for the presence of OC43 RNA. This human coronavirus was not detected.

The time course of repair of ultraviolet-induced DNA damage; implications for the structural organisation of repair

Alternative molecular mechanisms can be envisaged for the cellular repair of UV-damaged DNA. In the "random collision" model, DNA damage distributed throughout the genome is recognised and repaired by a process of random collision between DNA damage and repair enzymes. The other model assumes a "processive" mechanism, whereby DNA is scanned for damage by a repair complex moving steadily along its length. These two models give different predictions concerning the time course of repair. Random collision should result in a declining rate of repair with time as the concentration of lesions in the DNA falls; but the processive model predicts a constant rate of repair until scanning is complete. We have examined the time course of DNA repair in human fibroblasts given low (generally sublethal) doses of UV light. Using 3 distinct assays, we find no sign of a constant repair rate after 4 J/m2 or less, even when the first few hours after irradiation are examined. Thus DNA repair is likely to depend on random collision. The implications of this finding for the structural organisation of repair are discussed.

Rapid high-efficiency hemodialysis

Reductions in treatment time are attractive for patients and dialysis centers. However, there are concerns related to treatment adequacy and increased intradialytic symptoms. Treatment times were progressively reduced in 12 stable patients on standard 4-h acetate hemodialysis, solute clearances being increased proportionately, until the tolerance limit manifested by increased complications or 2.5 h of treatment was reached. Once shortened schedules (mean reduction approximately 31%) were achieved, a 2-month surveillance period was initiated, followed by 2 additional months of bicarbonate therapy, treatment time being unchanged. Rapid bicarbonate hemodialysis was associated with a significantly lower incidence of hypotension, nausea, and vomiting than rapid acetate or standard acetate therapies. Fluid removal was comparable with that of standard treatment, and serum chemistry levels remained stable. Based on the success of these studies treatment times have been reduced in greater than 200 patients with high-efficiency bicarbonate therapy for long-term evaluations.

Technical requirements for rapid high-efficiency therapies

Significant reductions in treatment time are possible with rapid high-efficiency hemodialysis and hemodiafiltration, provided the therapies are implemented so as to maintain adequacy of solute and fluid removal without compromising patient comfort. The key technical elements necessary for such implementation include high blood flow rates, higher efficiency dialyzers/diafilters, ultrafiltration control systems, and bicarbonate as the buffer source. In addition, hemodiafiltration requires schemes to ensure sterility and nonpyrogenicity of the infusion fluid and appropriate balancing of the rates of ultrafiltration and reinfusion. In general, rapid high-efficiency therapies are technically more complex than standard therapy, and rapid hemodiafiltration appears to be more complex than rapid hemodialysis. The technology required for rapid hemodialysis currently exists, but it needs to be fine-tuned and integrated for routine application.

Cisplatin and vinblastine chemotherapy for metastatic non-small cell carcinoma followed by irradiation in patients with regional disease

Forty-four patients with non-small cell carcinoma of the lung were treated every 3 weeks with vinblastine (4 mg/m2/day iv X 2) and cisplatin (20 mg/m2/day iv X 3). Of the 28 patients with metastatic disease, eight (29%; 90% confidence interval of true response, 17%-47%) achieved objective response, for a median duration of 27 weeks. Median survival in this group was 47 and 28 weeks for responders and nonresponders, respectively. Of the 16 patients with advanced regional disease, 11 (69%; 90% confidence interval of true response, 49%-86%) achieved objective response. Thirteen of these patients received consolidation radiotherapy (4500 cGy/25 fractions/5 weeks), with a boost of 1000 cGy/5 fractions/1 week in those patients who achieved response. In the three patients who did not receive radiotherapy, two died during the induction phase, one from grade 4 leukopenia and sepsis and the second from unrelated factors. The third patient had systemic progression of disease during induction chemotherapy. Six patients experienced overall improvement in their chemotherapy response from the radiotherapy. Two patients who did not respond to the chemotherapy achieved partial response with irradiation. Four patients who had partial response to the chemotherapy achieved complete response with irradiation, and seven patients had no further change in their degree of response to irradiation. The overall median survival of this group was 81 weeks. Maintenance chemotherapy was not given. After radiotherapy, the site of first failure was outside the radiation field in nine of 13 patients (69%). Hematologic toxicity was dose-limiting. Other toxic effects that were not dose-limiting included nephrotoxicity, neurotoxicity, and acute nausea and vomiting. In the patients with advanced regional disease, there was no increase in the radiation toxicity attributable to the chemotherapy. We conclude that: (a) this dose schedule of vinblastine and cisplatin has reproducible activity in non-small cell carcinoma of the lung; (b) the response and median survival of patients with advanced regional disease are superior to those of patients with metastatic disease; and (c) in patients with advanced regional disease, treatment with chemotherapy followed by radiotherapy yielded an overall response rate of 81% (90% confidence interval of true response, 60%-93%) and improved survival compared to a similar group of patients studied by others receiving radiotherapy alone. We recommend further testing of this concept.

Psychoneuroendocrine stress responses and mood as related to the menstrual cycle

Psychoneuroendocrine stress responses were studied in normally ovulating women in the follicular, ovulatory, and luteal phases of two consecutive menstrual cycles. Psychologic stress was induced by having the subjects perform a battery of cognitive tasks under time pressure. Blood samples were drawn after each session for radioimmunoassay of 17 beta-estradiol, progesterone, luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone, prolactin, cortisol, and androstenedione. Urine samples were obtained for estimation of adrenaline, noradrenaline, and cortisol. The results showed that psychoneuroendocrine stress responses as estimated by urinary excretion of adrenaline and noradrenaline varied significantly across the menstrual cycle, the highest values being obtained in the luteal phase. Self-reported mood and somatic symptoms showed distinct phase-related changes, with more negative mood states predominating in the luteal and menstrual phases and increased positive mood states in the follicular and ovulatory phases.

Macroaggregate formation in optimal additive red cells

The formation of macroaggregates weighing up to 9 g was observed in optimal additive red cells. Such aggregates, with a mean wet weight of 3 g, formed progressively during storage and were present in up to 85% of units. They were composed of leucocyte and platelet debris, together with some fibrin. Macroaggregates formation was halved by less stringent centrifugation during preparation and was reduced by use of an optimal additive system in which the additive solution contained citrate. Extra mixing during transfer of the additive solution only delayed aggregate formation. Partial leucocyte depletion or addition of 200,000 KIU of the enzyme inhibitor aprotinin did not prevent macroaggregate formation.

Blood pressure in Papua New Guinea: a survey of two highland villages in the Asaro Valley

The results of a population survey of blood pressure in the adult residents of two highland villages in the Asaro Valley, Papua New Guinea are reported. The survey was conducted in 1983 as part of a wider epidemiological investigation of non-communicable disease in Papua New Guinea. Response to the survey was 95%, and 308 subjects were examined. Population estimates of both systolic and diastolic blood pressures were low and there was a virtual absence of hypertension, as defined by internationally recommended criteria. There was no evidence of a rise in blood pressure with age, and the association between blood pressure and indices of obesity was weak. These findings are consistent with previous studies of blood pressure in traditional Papua New Guinean societies. The two villages differed with respect to their degree of modernisation. An unexpected finding was that in both sexes, both systolic and diastolic blood pressures were higher in the more traditional village. In each case, these differences were consistent across the three age groups examined, and they could not be explained by differences between the villages with respect to the indices of obesity. Analysis of variance showed that the higher blood pressures in the more traditional village were most unlikely to be due to chance (p less than 0.001). The explanation for this finding remains obscure.