Risk factors for macrovascular disease in diabetes mellitus: the London follow-up to the WHO Multinational Study of Vascular Disease in Diabetics

We have examined the relationship between baseline variables and the incidence of new macrovascular complications amongst the 497 members of the London cohort of the WHO Multinational Study of Vascular Disease in Diabetics over a mean 8.33-year follow-up. In univariate logistic regression analysis the incidence of new ischaemic electrocardiographic abnormality was significantly associated with systolic and diastolic blood pressure, diabetes duration and hypertension in patients with insulin-dependent diabetes, and with smoking in patients with non-insulin-dependent diabetes. New myocardial infarction was associated with systolic blood pressure, plasma cholesterol, proteinuria and smoking in patient with non-insulin-dependent diabetes; there were no significant associations among patients with insulin-dependent diabetes. All new ischaemic heart disease was associated with hypertension in patients with insulin-dependent diabetes, and plasma cholesterol and smoking in patients with non-insulin-dependent diabetes. New cerebrovascular disease was associated with systolic and diastolic blood pressure, ECG abnormality and hypertension. New peripheral vascular disease was associated with smoking. Multivariate analysis showed the following significant associations 1) in patients with insulin-dependent diabetes: ECG abnormality; hypertension, myocardial infarction; smoking, ischaemic heart disease; hypertension, diabetes duration and smoking, 2) in patients with non-insulin-dependent diabetes: ECG abnormality; smoking, myocardial infarction; serum cholesterol, proteinuria and smoking ischaemic heart disease; smoking. For new cerebrovascular disease, proteinuria and ECG abnormality were significant predictors in multivariate analysis. Patients with diabetes share many of the established risk factors for nondiabetic subjects, in addition proteinuria may be of significance in the prediction of macrovascular disease in diabetes.

The relationship between stress and the development of diabetic complications

Using the Life Events and Difficulties Schedule of Brown and Harris, the relationship between preceding stress and the onset of diabetic complications and premature death was investigated prospectively in a random sample of 130 patients with diabetes, aged 35-59 years. The presence of stress, assessed as severe life-events and severe long-term difficulties, was not significantly associated with premature death or the onset of macrovascular disease over the relatively short period of follow-up (4 years). Those who commenced anti-hypertensive therapy during the follow-up period were significantly more likely to have experienced five or more severe life-events during the previous 5 years (40 vs 6%, p less than 0.01), and also to have experienced one or more severe long-term difficulties during the same time period (60 vs 28%, p less than 0.05). A multiple Cox regression analysis showed that the effects of stress were independent of other factors such as baseline blood pressure, type of diabetes, sex, and ethnic group.

A prospective study of mortality among middle-aged diabetic patients (the London Cohort of the WHO Multinational Study of Vascular Disease in Diabetics) II: Associated risk factors

Potential risk factors have been examined for association with mortality over a 10-12 year follow-up of the patients of the London Cohort of the WHO Multinational Study of Vascular Disease in Diabetics (aged 35-54 years at entry to the study). Proteinuria has the strongest association with all-cause mortality in univariate analysis being significant in patients of both sexes with Type 2 (non-insulin-dependent) diabetes mellitus and in women with Type 1 (insulin-dependent) diabetes mellitus; both systolic blood pressure (men) and hypertension (both sexes) (as a categorical variable) are significant in Type 1 diabetes. Hypertension is also significantly associated with all-cause mortality in multivariate analysis in both sexes with Type 1 diabetes as proteinuria is in women with Type 2 diabetes. There is an unexpected negative association between plasma creatinine and all-cause mortality in men with Type 2 diabetes. Systolic blood pressure and hypertension are also significantly linked with cardiovascular mortality in Type 1 diabetes, hypertension having an estimated relative risk of 4.6 [corrected] in multivariate analysis. Serum cholesterol and proteinuria showed the strongest associations with cardiovascular mortality in Type 2 diabetes. Proteinuria is associated with non-cardiovascular mortality in both types of diabetes in univariate but not multivariate analysis. In multivariate analysis hypertension (Type 1 diabetes) and diabetes duration (Type 2 diabetes) are associated with non-cardiovascular mortality. Hypertension and proteinuria have the most consistent associations with mortality in the different analyses with the effect of hypertension appearing stronger in Type 1 diabetes and proteinuria in Type 2 diabetes.(ABSTRACT TRUNCATED AT 250 WORDS)

A prospective study of mortality among middle-aged diabetic patients (the London Cohort of the WHO Multinational Study of Vascular Disease in Diabetics) I: Causes and death rates

The 497 members of the London Cohort of the WHO Multinational Study of Vascular Disease in Diabetics have been followed for mortality from 1975 to 1987. During this period 92 patients died. The most common cause of death was myocardial infarction: 36 (39.1%) deaths, heart disease was responsible for 51.1% of deaths and all cardiovascular disease for 55.4%. Neoplastic disease accounted for 25% of the deaths and diabetic nephropathy for 5.4%. Age-standardised mortality rates were higher in men than in women in both Type 1 (insulin-dependent) diabetes and Type 2 (non-insulin-dependent) diabetes. Standardised mortality ratios for the first and second five year follow-up periods were higher for men than for women in Type 2 diabetes but were higher for women than men in Type 1. The results suggest that the female survival advantage seen in the general population may persist in Type 2 but not in Type 1 diabetes.

International variations in mortality among diabetic patients: the WHO Multinational Study of Vascular Disease in Diabetics

Mortality among 4740 diabetic men and women aged 35-55 years participating in the WHO Multinational Study of Vascular Disease in Diabetics has been studied. Ten of the original centres (Warsaw, Berlin, Havana, Arizona, Oklahoma, Hong Kong, Switzerland, London, Tokyo, Zagreb) were able to identify the life/death status of their study participants on 1 January 1983, giving an average follow-up period of six to seven years. All-cause mortality rates in males varied about threefold among the ten participating centres with the highest rates in Warsaw, Berlin and Havana and the lowest rates in Tokyo and Zagreb. All-cause mortality rates for females varied about fourfold with the highest rates in Warsaw and Oklahoma and the lowest rates in Tokyo. The proportion of deaths ascribed to circulatory disease varied among the centres ranging from 32% for males and 0% for females in Tokyo to 67% for males and 47% for females in London. There was an excess all-cause mortality in males compared to females for all centres except Zagreb. This excess also applied to circulatory diseases in general, ischaemic heart disease in particular and occurred in both insulin-dependent and non-insulin-dependent diabetic patients. Death rates for insulin-dependent diabetic patients were generally higher than those for non-insulin-dependent patients.

Validity of routinely collected hospital admissions data on diabetes

Data from the clinical records of patients known to have diabetes and admitted to hospital in North West London, Cambridge or Newcastle were compared with data on the same admissions taken from the system responsible for recording information on all acute hospital admissions (Hospital Activity Analysis). In 89 out of 751 admissions (12%), either the sex, date of birth or marital status of the patient was incorrectly recorded. The diagnosis of diabetes was omitted in 32 (10%) of 315 admissions in which diabetes or a complication of diabetes was regarded as the principal cause of admission and in 12 (23%) out of 53 in which the principal cause was closely related to diabetes. These included cases in which the diagnosis had not been stated (by the clinician) on the discharge summary (the source document for Hospital Activity Analysis) as well as instances in which the coding clerk had failed to record the diagnosis. The validity of information collected on hospital admissions is dependent on the presentation of data by the clinician to the coding clerk. There may be a lack of awareness of the importance of the clinical discharge summary as a source document for such systems.

Psychosocial factors and the onset of type 1 diabetes

Stress has been proposed as a possible precipitating factor for the development of Type 1 diabetes in genetically susceptible individuals. A validated in-depth psychometric instrument (The Life Events and Difficulties Schedule) was used to investigate the role of psychosocial factors in the onset of Type 1 diabetes in islet cell antibody (ICA)-positive family members. Families with ICA-positive members had higher scores for subject focused severe life events in the 5-year period prior to the diagnosis of diabetes in a second family member compared with matched control families (1.50 +/- 0.68 (+/- SD) vs 0.32 +/- 0.37; p less than 0.03). In the same time period, these families also experienced a higher mean number of severe long-term difficulties compared with control families (1.34 +/- 0.52 vs 0.14 +/- 0.17; p less than 0.01). Scores for current total visual social contacts were greater for control families compared with case family members (12.10 +/- 1.90 vs 9.64 +/- 2.70; p less than 0.05). These results suggest that global family stress possibly in conjunction with a reduced number of social contacts may act as a trigger for the development of diabetes in a second family member and that social support may act as a buffer to stress and disease onset.

Depression and diabetes

The incidence and prevalence of depression in diabetic patients in the United Kingdom is unknown. Since depression may influence blood glucose control which in turn may be related to the development of diabetic complications, it is important to estimate its prevalence in diabetic patients. The prevalence of depression was investigated in a group of Caucasian and West Indian, insulin-(IDDM) and non-insulin-dependent (NIDDM) adult diabetics and a non-diabetic comparison group. Prevalence of depression was 8.5% for both groups and a further 19.2% and 14.6%, respectively, had borderline depression. Presence of depression was unrelated to sex, ethnic group, duration or type (IDDM or NIDDM) of diabetes and social class but significantly related to type of accommodation, marital status, and amount of social contact. A higher percentage of diabetics with psychiatric symptoms had one or more current complications compared to 'normal' diabetics. Diabetics suffer from a similar amount of depression to non-diabetics, but psychiatric symptoms may be related to the frequency of diabetic complications.

The relationship of high density lipoprotein subfractions to alcohol consumption, other lifestyle factors, and coronary heart disease

Serum high density lipoprotein (HDL) levels are inversely related to the risk of coronary heart disease. Controversy exists regarding the relative importance of HDL subfractions, and few studies have related subfraction levels to lifestyle factors associated with coronary risk. We examined the relationship of the major subfractions, HDL2 and HDL3, to alcohol consumption, cigarette smoking, physical exercise, body mass index, and socioeconomic status in 88 men and 49 women aged 35-64 years. Body mass index was inversely related to HDL2-cholesterol (C), particularly in men, but had no significant relationship with HDL3-C. Cigarette smoking and degree of physical exercise were not significantly related to either HDL subfraction. Alcohol consumption had a strong positive correlation with HDL3-C in both sexes; this association was statistically significant after controlling for cigarette smoking, body mass index, and serum triglyceride. Minnesota-coded ECG abnormalities and positive responses to the WHO chest pain questionnaire were associated with lower levels of HDL-C and HDL2-C in both sexes, and significantly lowered levels of HDL3-C in men but not women. These findings suggest that HDL3-C, as well as HDL2-C, may be related to coronary risk, and indicate that the protective effects of alcohol consumption may be mediated via this subfraction.

Head movements during optokinetic stimulation in the alert rabbit

Pigmented rabbits with their heads free to move about the vertical axis were seated inside a rotating optokinetic drum in order to evoke the optocollic reflex (OCR). At drum velocities below 5 degrees/s, head movements were inconsequential, and eye velocity generally matched drum velocity. At velocities between 5-15 degrees/s head movements were irregular and slight; head velocity was less than 20% of drum velocity, and gaze was undercompensatory by 1-3 degrees/s (retinal image motion of 1-3 degrees/s). At drum velocities above 15 degrees/s, and especially above 30 degrees/s, head movements were substantial (more than 20% of the drum velocity), but gaze was undercompensatory by 60-70% of the stimulus velocity. In the same rabbits in the same test periods and conditions, the vestibulo-collic reflex (VCR) was evoked with vision with minimal gaze undercompensation relative to a stationary surround; however, when deprived of vision the VCR gain dropped. The present results support the notion that with vision, the OCR does not contribute significantly to the improvement of the VCR response, since massive undercompensation of the gaze relative to the rotating drum was required in OCR testing to evoke head movements similar to those seen in VCR tests. Due to many differences in operating characteristics of the vestibular and optokinetic systems, and due to the nature of OCR testing, there were several unexpected results: in some cases head movements did not result in summation of vestibular and optokinetic reflexes, and with sinusoidal drum rotations of about 2 degrees/s2 peak acceleration there was overcompensation (gaze moves faster than the drum) for intervals up to 20 s. Thus, optokinetically generated active head movements could produce behavior strongly contrasting with passively induced head movements in visual-vestibular tests. It is tentatively concluded that in mammals there is a vestigial and specific optokinetic control of gaze and that the optokinetic control of the head is weak (relative to the eyes). However, other non-reflex mechanisms controlling head movements-such as stimulus entrainment and temporal asymmetries in the vestibular and optokinetic reflexes-must also be considered to explain all facets of the data.

The force-velocity relation of the rabbit digastric muscle

In 30 animals, the digastric was made to pull actively against a slide loaded by a servo-controlled linear motor. Force and velocity were recorded at the end of active shortening to the in-situ (jaw-closed) muscle length. Passive and active force-length relations were also determined in 17 of the rabbits. The empirical force-velocity data were fitted to a hyperbolic equation. The average speed of muscle shortening at zero load was 14.67 cm/s. Mean maximum isometric force at in-situ length (P0) was 1267 g, and the mean ratio a/P0 was 0.18. The average time-to-peak twitch tension was 31.8 ms under isometric conditions. In-situ muscle-belly length was about 3 per cent less than optimum length for isometric force. Maximum muscle force was positively correlated with animal size, but maximum velocity showed no relation to force or length. The estimated maximum speed of sarcomere shortening was 26 micron/s, which is slightly slower than in fast limb muscles of the cat, and may indicate the presence of both histochemical type I and II fibres. The isometric force after shortening had ceased was less than P0, and was correlated with the velocity during shortening. This depression of isometric force may result from an alteration of the excitation-coupling system during activation. These observations suggest a role for the digastric in the rapid acceleration and deceleration of the mandible near the jaw-closed position during opening and closing.

Epidemiology of hypertension associated with diabetes mellitus

The clinical impression of an association between hypertension and diabetes mellitus has not been consistently confirmed by epidemiological studies. The variety of methodological problems in this area of research includes the choice of appropriate patient and control groups, the measurement techniques used, and consideration of many possible confounding variables. Several prospective studies have shown that hypertension may be a potent risk factor for diabetic macrovascular and microvascular disease. This relationship may have important preventive implications, and raises the question of the optimal antihypertensive therapy in diabetic patients.

Cervicocollic reflex: its dynamic properties and interaction with vestibular reflexes

Electromyographic activity of dorsal neck muscles elicited by sinusoidal rotations of the body and head was studied in decerebrate cats over a wide range of rotational frequencies and amplitudes. Rotation of the body with the head held fixed in space elicited a cervicocollic reflex (CCR) in the biventer cervicis, complexus, obliquus capitis inferior, rectus capitis major, and splenius muscles. As stimulus amplitude increased, CCR amplitude increased first rapidly and then more slowly, displaying two linear incremental sensitivity ranges. In contrast, the vestibulocollic reflex (VCR) elicited by whole body rotation had a minimum stimulus threshold below which no response was observed, whereas the vestibuloocular reflex (VOR) saturated at intermediate stimulus intensities. When stimulus frequency was varied, the CCR exhibited second-order dynamic behavior. At frequencies below 0.5 Hz, muscle EMG activation was in phase with peak platform angular deviation in the direction that stretched the muscle, and the gain measured as the percent modulation of EMG activity per degree of rotation remained constant. As frequency increased to 3-4 Hz, response phase advanced by 120 deg or more and gain increased with a slope approaching 40 dB/decade. The data were well-fitted by second-order transfer functions containing two zeros. Both the dynamic behavior of the CCR and its high sensitivity to small stimuli resemble the properties of muscle spindle primary afferents, suggesting that the latter may provide the major input responsible for the CCR. Dynamic properties and gains of the CCR and VCR were quite similar at frequencies between 0.2 and 3-4 Hz. Transfer functions of both reflexes contained two zeros whose time constants were correlated in a population of 11 cats, suggesting that reflex dynamics may be matched to the mechanical properties of each animal's head-neck system. Interaction of the CCR and VCR was studied under two conditions. When the head was driven by a servomotor while the body remained stationary, EMG activation by the two reflexes added linearly to produce a large response. When the body was rotated with the head allowed to counterrotate about the C1-C2 joint, the two reflexes combined linearly in an antagonistic fashion: the CCR acted to oppose head rotations produced by the VCR, thus preventing the ratio of head counterrotation to body rotation from exceeding 0.5. The data indicate that the CCR and VCR behave approximately linearly, both individually and in combination. Acting together, the two reflexes assist each other in preventing oscillation of the head on a stationary body.(ABSTRACT TRUNCATED AT 400 WORDS)

Role of life events and difficulties in the onset of diabetes mellitus

The role of stressful life and difficulties in the onset of insulin-dependent (Type 1) diabetes mellitus was examined in a group of 13 newly diagnosed diabetics and sibling and neighbourhood controls. Subjects aged between 17-34 years, were interviewed and information was collected over the 3 year period preceding clinical diagnosis of diabetes. Diabetics had a higher frequency of one or more severe life events prior to diagnosis i.e. 77% compared with their siblings and age/sex matched controls i.e. 39% and 15% respectively. Diabetics also had a higher percentage of 2 or more severe life events prior to diagnosis i.e. 54% compared with 8% for siblings and 8% for neighbourhood controls. The frequency of severe difficulties was also higher for diabetics--46% compared with 13% and 23% for siblings and neighbourhood controls respectively. Stressful events and difficulties may be triggering factors involved in the aetiology of insulin-dependent diabetes.

Eye and head movements in the pigmented rat

Vestibular, optokinetic, and spontaneous eye and head movements have been examined in the hooded rat. Eye movement range was 18-20 degrees, and frequency of ocular saccades was 5-20/min; there was a weak linkage of eye and head movements and a weak vestibulocollic reflex. Response to optokinetic stimulation with unity gain (eye velocity matches drum velocity) was seen only at velocities below 1 deg/sec; maximal eye velocity evoked by drum velocities of over 20 deg/sec never exceeded 4-6 deg/sec. These motor responses were not altered by head movements: thus, gaze velocity is not improved by optocollic (head movement) responses, and such optocollic activity occurs only when substantial retinal image motion is present.

Social class and risk factors for vascular disease in diabetes

Mortality statistics for England and Wales and for the U.S.A. indicate that death rates from diabetes mellitus are higher in the lower socioeconomic classes. In an attempt to explain this mortality difference, social-class differences in possible risk factors for the large- and small-vessel disease complications of diabetes have been examined in 95 insulin dependent diabetics (IDDs) and 79 non-insulin dependent diabetics (NIDDs) and comparative data obtained from 155 non-diabetic controls. Control males in the lower social class group were significantly shorter, more obese, smoked more and had lower Type A behaviour scores. Lower class female controls had significantly higher serum cholesterol levels. For the diabetic groups there were no social class differences in either fasting blood glucose levels or the prevalence of diabetic complications. Lower class NIDDs were significantly shorter and had lower Type A scores. This group also had higher mean cholesterol levels and smoked more, but these differences did not achieve statistical significance. Male IDDs showed no significant social class differences in possible risk factors but lower class females IDDs smoked more and had higher mean triglyceride levels. This concentration of risk factors for vascular disease in the diabetics of lower social class, particularly the NIDDs, may partly explain the increased mortality found in this group.

Mortality from coronary heart disease and stroke in relation to degree of glycaemia: the Whitehall study

In the Whitehall study of 18 403 male civil servants aged 40-64 years the 10 year mortality rates from coronary heart disease and stroke showed a non-linear relation to two hour blood glucose values, with a significantly increased risk for glucose intolerant subjects with concentrations above the 95th centile point (5.4-11.0 mmol/l; 96-199 mg/100 ml) and for diabetics (blood glucose greater than or equal to 11.1 mmol/l; greater than or equal to 200 mg/100 ml). Multiple logistic analysis showed that between one half and three quarters of the relative risks for deaths from coronary heart disease and stroke were "unexplained" by between group differences in risk factors such as age, blood pressure, obesity, smoking, cholesterol concentration, and electrocardiographic abnormalities. Within the glucose intolerant and diabetic groups the risk factors most strongly related to subsequent death from coronary heart disease were age and blood pressure, with less consistent relations for smoking, cholesterol concentration, and obesity. This study confirms the importance of hypertension as a cardiovascular risk factor in groups with glucose intolerance and diabetes, and this may have important preventive implications.

Vestibular-oculomotor interaction in cat eye-head movements

When cats make slow scanning head movements, intersaccadic counterrotary eye movements are driven by the vestibulo-ocular reflex, but reset or forward saccades are not directly affected by vestibular afference. When the movements are rapid (approximately 200 deg./sec), large (greater than 40 degrees), and executed in single step shifts gaze (whether in the dark or during visual fixation shifts between known targets), there is no longer any clear vestibular effect on any eye movements during the gaze shift. The vestibulo-ocular reflex is active only at the beginning of head rotation and again at its termination as the gaze reaches its goal, even in the absence of vision. It is postulated that head-in-space and eye-in-orbit movements are perfectly monitored to adjust the amplitude of gaze shifts, despite the lack of overt vestibular effects on eye movements.

The role of circulating glucose and triglyceride concentrations and their interactions with other "risk factors" as determinants of arterial disease in nine diabetic population samples from the WHO multinational study

In 9 of the 14 national samples of diabetic patients assembled for the WHO Multinational Study of Vascular Disease in Diabetes additional laboratory data made it possible to relate manifestations of macrovascular disease to blood glucose concentrations as well as to diabetes duration and to other potential determinants. In five of the samples, serum triglyceride concentrations were also measured and were included in simple and multivariate analyses. Ischemic heart disease defined from Minnesota-coded EKGs and standardized WHO questionnaires was more strongly associated with serum triglyceride concentrations than with serum cholesterol concentrations, an association less notable in non-insulin-dependent diabetic patients. Ischemic heart disease was not related to the single fasting plasma glucose estimated for this study. Stroke and amputation were much more strongly related to the known duration of diabetes than was ischemic heart disease, and they were both related to blood glucose concentration measured at the time of study. Despite major variation in arterial disease prevalence rates between collaborating centers, risk for diabetic women appeared to equal that for diabetic men. The major variation in arterial disease prevalence between national groups could be accounted for only in part by the risk factors studied. Other factors, genetic or more likely environmental, are likely to contribute to the variation in arterial disease susceptibility and, if definable, may be potentially preventable.

Diabetes mortality: new light on an underestimated public health problem

Mortality from diabetes is underestimated four- to fivefold by methods of analysis of death certification data which use only underlying cause of death. This problem is partially overcome by coding all conditions mentioned on death certificates. For a sample of deaths in England and Wales over the years 1972-1977, the observed proportion of certificates with specific underlying causes of death for certificates mentioning diabetes was compared with the expected proportion for all certificates. These observed/expected ratios were significantly increased in each sex for circulatory diseases and were significantly reduced for neoplasms. For 'nephritis' they were also increased, especially below 45 years of age. These results were confirmed by an analysis of underlying cause of death in a cohort of nearly 6,000 members of the British Diabetic Association. Of the 2,134 deaths in this cohort, diabetes was not mentioned on 33% of the death certificates. For the period 1972-1977, death rates for circulatory diseases associated with diabetes increased by 6% for males but remained constant for females.

High density lipoprotein subfractions in insulin-dependent diabetic and normal subjects

Serum lipoproteins have been separated by preparative ultracentrifugation in randomly selected groups of insulin-dependent diabetics and in age- and sex-matched non-diabetic controls. The major high density lipoprotein (HDL) subclass; HDL2 (density (d) 1.063-1.125 kg X m-3) and HDL3 (d greater than 1.125) and the further fractions of HDL2:HDL2b (d 1.063-1.100) and HDL2a (d 1.100-1.125) were also separated and their cholesterol (C) concentrations determined. These diabetic men and women were relatively normolipaemic and the major difference from controls was a significantly raised total HDL-C in men which was confirmed by a separate chemical precipitation method. This increase was associated with a significant rise in HDL2a-C and in total HDL2-C concentration. The non-significant increase in diabetic women compared to men was associated with poorer metabolic control. Among factors influencing serum HDL2-C concentration, the most important was the negative association with the level of very low density lipoprotein-triglycerides. Although insulin-dependent diabetics have an increased risk of atherosclerotic coronary heart disease (CHD), this is not reflected in their HDL subfraction-C distribution which, if present in non-diabetics, would be expected to confer protection from CHD.

Interrelationships of microangiopathy, plasma glucose and other risk factors in 3583 diabetic patients: a multinational study

In a multinational study, fasting plasma glucose values in 3583 diabetic patients, aged 34-56 years, were related to the characteristics of these subjects and to the presence and severity of microangiopathy as ascertained by standardised methods. The patients were from nine different populations and ranged in number from 193 to 686 per population (London, Warsaw, Berlin (FRG), New Delhi, Tokyo, Havana, Oklahoma Indians, Arizona Pima Indians, and a national sample in Switzerland). In the total group, mean fasting plasma glucose was 8.1 mmol/l for those on diet alone, 9.7 mmol/l for those on oral agents, and 12.7 mmol/l for insulin-treated patients, of whom 25% had values exceeding 16.5 mmol/l. Since many variables were measured in each patient, it was possible to take into account many confounding factors in evaluating the relationship of plasma glucose levels to retinopathy and nephropathy.

Eye and head movements during vestibular stimulation in the alert rabbit

Rabbits passively oscillated in the horizontal plane with a free hand tended to stabilize their head in space (re: earth-fixed surroundings) by moving the head on the trunk (neck angular deviation, NAD) opposite the passively imposed body rotation. The gain (NAD/body rotation) of head stabilization varied from 0.0 to 0.95 (nearly perfect stability) and was most commonly above 0.5. Horizontal eye movement (HEM) was inversely proportional to head-in-space stability, i.e. the gaze (sum of HEM, NAD, and body rotation) was stable in space (regardless of the gain of head stabilization). When the head was fixed to the rotating platform, attempted head movements (head torque) mimicked eye movements in both the slow and fast phases of vestibular nystagmus; tonic eye position was also accompanied by conjugate shifts in tonic head torque. Thus, while eye and head movements may at times be linked, that the slow eye and head movements vary inversely during vestibular stimulation with a free head indicates that the linkage is not rigid. Absence of a textured stationary visual field consistently produced a response termed 'visual inattentiveness,' which was characterized by, among other things, a reduction of head and gaze stability in space. This behavioral response could also be reproduced in a subject allowed vision during prolonged vestibular stimulation in the absence of other environmental stimuli. It is suggested that rabbits optimize gaze stability (re: stationary surroundings), with the head contributing variably, as long as the animal is attending to its surroundings.

Hyperglycemia and arterial disease

Clinical and autopsy evidence support the increased risk of atherosclerotic disease in diabetes mellitus (DM). However, mechanisms other than arterial occlusion may also contribute to clinical syndromes often assumed to be atherosclerotic in origin. There is considerable geographical variability in the frequency of arterial disease in the diabetic. Glucose intolerance short of unequivocal DM is found in some (though not all) populations to carry increased atherosclerotic risk. Morbidity and mortality data suggest that women are particularly vulnerable (as with DM). The Whitehall prospective study of cardiovascular mortality shows that risk does not rise smoothly with increasing degrees of glucose intolerance but that it doubles sharply at the 95th percentile of the 2-h post-glucose blood sugar distribution.

The dynamic neck-eye reflex in mammals

Stimulation of cervical proprioceptors by torsion of the neck results in movement of the eyes. The pathways of this neck-eye reflex have been identified electrophysiologically, and in individuals with vestibulo-ocular deficits the reflex is often seen to contribute to retinal image stability during head movements. In intact individuals, however, its role in ocular compensation for head movements is questionable. In this and other studies, the reflex eye movements were in the direction opposite the vestibulo-ocular reflex and were, therefore, anticompensatory. In four species of mammal (rat, rabbit, cat, and bush baby - a primate), the reflex was most consistently elicited with an anticompensatory phase; furthermore, when an animal partially stabilizes its head in space (by the vestibulo-collic reflex) during body rotation, the vestibulo-ocular and neck eye reflexes must have opposite polarities if their summation is to be of use to the animal. The neck-eye reflex appears to be absent when the animal actively moves its head; it only appears during the experimental procedure employed to elicit the reflex. An alternative function for the electrophysiologically identified pathway of the neck-eye reflex is suggested.

Coronary-heart-disease risk and impaired glucose tolerance. The Whitehall study

In the Whitehall Study of 18,403 male civil servants aged 40--64 years, 7 1/2 year coronary-heart-disease (CHD) mortality has been examined in relation to blood-sugar concentration 2 h after a 50 g oral glucose load. CHD mortality was approximately doubled for subjects with inpaired glucose tolerance (IGT), defined as a blood-sugar above the 95th centile (greater than or equal to 96 mg/dl). There was no trend of CHD mortality with blood-sugar below the 95th centile. Within the IGT group, age, systolic blood-pressure, and ECG abnormality (Whitehall criteria) were significantly predictive of subsequent CHD mortality. These findings are relevant to discussions on the criteria for diabetes which include the definition of an IGT category with increased risk of large-vessel disease, but without the high risk of small-vessel disease as occurs in diabetes mellitus.

Lipoproteins and plasma cholesterol esterification in normal and diabetic subjects

Serum lipoproteins, separated by preparative ultracentrifugation and the activity of the plasma enzyme lecithin: cholesterol acyltransferase (LCAT) have been measured in insulin-dependent diabetics, non-insulin-dependent diabetics and in age-matched non-diabetic controls. In the insulin-dependent diabetics, mean total serum cholesterol and high density lipoprotein cholesterol (HDL-C) concentrations were significantly higher than in controls. Non-insulin-dependent diabetics had significantly raised total triglycerides and cholesterol, but HDL-C levels were essentially normal. The increased low density lipoprotein cholesterol (LDL-C) in both diabetic groups was statistically significant in men. A methodological study of HDL separation techniques was carried out to facilitate interpretation of these findings. Mean LCAT activity, by a method reflecting combined enzyme and substrate effects was significantly increased in these diabetic groups. The results confirm recent reports of a raised HDL-C in those insulin-dependent diabetics who are prone to coronary heart disease.

Haemostatic variables associated with diabetes and its complications

To study the possible role of an "increased thrombotic tendency" in the vascular complications of diabetes several tests of haemostatic function were carried out on 91 men and 63 women with diabetes aged 35-54 years and the results compared with findings in 686 men and 393 women of the same age in the Northwick Park Heart Study. Mean values for factors VII and X, fibrinogen, and platelet adhesiveness were higher in the diabetics, but mean fibrinolytic activity and whole blood platelet counts were lower. Antithrombin III values were also higher in the diabetics, which may have constituted a protective response to other changes favouring the onset of vascular disease. Diabetics with retinopathy had higher factor VII and antithrombin III values, and those with proteinuria had higher values for factor VII, fibrinogen, and platelet adhesiveness than those without these complications. These findings suggest a potentially important association between a thrombogenic tendency and vascular disease in diabetes. Nevertheless, prospective data are needed to clarify whether the haemostatic abnormalities precede the onset of clinically manifest vascular complications or are a consequence of them.

Nutrient intake, adiposity, and diabetes

To study the role of nutritional factors in the genesis of diabetes, estimations of blood sugar concentration, food intake, and adiposity (as body mass index; BMI) were carried out on three normal population samples--namely, 961 employees of Beecham Ltd, 1005 employees of the Greater London Council, and 1488 middle-aged male civil servants (Whitehall study). Blood sugar concentrations and indices of glucose tolerance correlated positively with the degree of adiposity but tended to be negatively correlated with total food energy intake and its component nutrients (total carbohydrate, sucrose, and fat). This inverse trend was largely accounted for by highly significant inverse correlations between food energy intake and adiposity, a relation found in both sexes and in all three population samples and which extended across the whole range of nutrient intake and BMI. These findings suggest that greater degrees of adiposity are associated with lower than average food energy intakes and hence lower total energy expenditures. The association of increased adiposity with low food energy consumption may indicate an underlying "low energy throughput" state, and it may be the mechanisms of this, as well as the obesity, that are responsible for disease.

Worsening to diabetes in men with impaired glucose tolerance ("borderline diabetes")

Two hundred and four men with impaired glucose tolerance (borderline diabetes) discovered in a screening examination have been observed for five years and repeated tests of glucose tolerance performed. By pre-determined criteria 27 men 'worsened to diabetes' and this metabolic deterioration was not significantly influenced by treatment with carbohydrate restriction with or without a daily dose of 50 mg phenformin. Of the baseline variables measured prior to treatment allocation only the blood glucose values were significantly predictive of ultimate worsening to diabetes.

Glucose tolerance and blood pressure in two population samples: their relation to diabetes mellitus and hypertension

The relationship between blood pressure and the blood sugar concentration measured two hours after a 50 g oral glucose load has been examined in two population surveys-the Whitehall and Bedford Surveys. In the Whitehall Survey, which was conducted in men above the age of 40, there was a positive, significant correlation between blood sugar and blood pressure (systolic and diastolic) which was independent of common associations with age, body mass index (BMI) and heart rate. In the Bedford Survey, systolic blood pressures were significantly higher in newly detected diabetics and borderline diabetics, both men and women, than in normoglycaemic controls after adjustment of blood pressures for age and BMI. However, in the stratified random sample of the cooperating Bedford population, only amongst women was the blood sugar significantly and independently correlated with the systolic blood pressure. Evidence is presented and discussed that autonomic, neurohumoral factors may play some part in the pathogenesis of maturity onset diabetes.

Treatment of borderline diabetes: controlled trial using carbohydrate restriction and phenformin

A five-year therapeutic trial of carbohydrate restriction with or without phenformin (50 mg/day) was performed in men with borderline diabetes. The aim of treatment was to diminish the enhanced risk of cardiovascular disease and deterioration of glucose tolerance. Cardiovascular morbidity and mortality were not significantly affected by any form of treatment, alone or in combination. The predominant risk factor for cardiovascular morbidity and mortality and for overall mortality was the initial blood pressure level. The baseline plasma cholesterol concentration significantly predicted the onset of intermittent claudication. One implication of the results is that hypotensive treatment, supplemented when necessary with hypolipidaemic treatment, may be more effective in preventing the progression of arterial disease in people with mild to moderate glucose intolerance than conventional antidiabetic therapy.

Determination of antidromic excitation by the collision test: problems of interpretation

Extracellular unit recordings were made from pontine reticular neurons in the cat and cells of the motor cortex in monkeys. In all cases, the characteristics of responses to electrical stimulation were studied using the tests of invariance of latency, high frequency following, and collision for determining the orthodromic or antidromic nature of the responses. The results of these tests show that their conclusions are not always consistent. A systematic error was found between the experimental and predicted values of the collision interval. It is argued that this error is due to differences in the application of measured parameters in calculating the collision interval. The collision test can be considerably improved by repeating the test with stimuli of progressively greater strengths.

Brain stem reticular units: synaptic responses to stimulation within the ascending reticular pathways

When the ascending reticular axonal system is stimulated, the responses of distal structures (e.g., the cerebral cortex) appear to outlast the stimulus; these longlasting effects could reflect the intrinsic nature of the distal structure, or the response could reflect an interaction among the reticular cells which tends to prolong the effects of stimulation. To examine the latter hypothesis, single units with ascending axons (projecting units) were recorded in the cat rostral rhombencephalon in acute experiments conducted under halothane-nitrous oxide anesthesia. Stimulation of areas to or through which axons of reticular neurons projected (midbrain tegmentum and lower tectum, medial thalamus, and basal forebrain) produced a consistent and specific response which was elicited only from these areas: suppression of spontaneous activity which was typically elicited from several areas having ascending axons. One-half of these responses were accompanied by a short latency-single spike synaptic excitation. Stimulating areas more than 1.0 mm from the ascending trajectory never produced this response, whereas the number of responses was directly related to the number of projecting axons identified in any one experiment from a given site. Thus, the predominant effect of stimulating within the ascending axonal trajectory was suppression of spontaneous activity in the projecting units, not an 'en cascade' activation of these units; on the contrary, the only type of excitation encountered was a single, short latency spike. Therefore, any effects of stimulation within the ascending reticular pathway which appear to outlast the stimulus (as previously described in the literature) cannot be ascribed to a reverberating (excitatory) circuit among projecting units. A possible source of the synaptic responses of projecting units is a retrograde activation of collaterals interconnecting the reticular cells. If such interaction exists, it is specifically distributed among cells with ascending axons, as the responses were only observed in a very few units not identified by antidromic excitation; however, other evidence is adduced to support the belief that these few units were projecting units whose axons were beyond the reach of the stimulating electrodes. Futhermore, the axons may be bundled such that units with axons nearest that of a given projecting unit give rise to the most extensive synaptic interactions; the activation of these nearby axons suppresses spontaneous activity, while axons farther away have a greater possibility of being excitatory in nature. Should such a medium for interaction exist, reticular collateral interactions might be seen to exist specifically for the purpose of decreasing the activity of cells destined for similar rostral target structures.

Visual tracking and the primate flocculus

Purkinje cells in the primate flocculus discharge specifically in relation to visual tracking, effectively generating a velocity profile of the target during pursuit. It is suggested that these neurons supply oculomotor centers with the velocity command signals needed to support pursuit eye movements.

Brain stem reticular units: some properties of the course and origin of the ascending trajectory

Experiments were conducted in acutely prepared cats anesthetized with halothane-nitrous oxide. Single units were recorded in the mesencephalic and rostral rhombencephalic reticular core, and their ascending axons were stimulated in the mesencephalon, diencephalon, and telencephalon. The locations of stimulation and recording sites were determined by histological examination of the brains. Antidromic spikes were elicited by electrodes with a stimulus spread of approximately 300 mum and were collided with spontaneous (orthodromic) spikes to confirm antidromicity. Projecting axons were found to be scattered diffusely in the central mesencephalon in both the tegmentum and tectum. At the mesodiencephalic junction, the dorsal extent of the pathway lay in the posterior commissure and the ventral extent in the substantia nigra. More rostrally, a ventral group of axons was found in or near the supraoptic nucleus in the hypothalamus, and near the floor of the forebrain in the basal telencephalon. In agreement with previous reports, a dorsal component was located in the medial thalamus, most often in the nucleus centralis lateralis. The conduction velocity of each axon was determined, and they suggest a wide range of axon size in the ascending pathways. There may be a slight predominance of smaller fibers in the dorsal component and of larger fibers in the ventral component; however, all parts of the pathways were relatively heterogenous. The units from which projecting axons arose were found in the rostral rhombencephalon, and no units sending their axons along the restricted pathways investigated were identified rostral or caudal to this region. However, no conclusion is drawn concerning units within the region extending from 0.0 to 0.6 mm of the midline or other brain stem regions known to be monoamine-rich and to have ascending axons; these cellular populations were not examined.