Perineurium: evidence for contractile elements.

Electron-microscopic study of mouse sciatic nerve reveals that perineurial cells contain filaments and associated opaque regions similar to those observed in smooth muscle. This finding is consistent with obsevations Which suggest that nerve might have a contractile property. In addition to their function in maintaining the connective tissue stroma of perineurium, as well as being a selective diffusion barrier, perineurial cells may serve the nerve in a contractile capacity.

Contractile cells in human seminiferous tubules.

Electron microscopic study of the peritubular connective tissue in human testis reveals the presence of "contractile-type" cells rather than of typical fibrocytes. Their cytoplasm has numerous fine filaments and other components. characteristic of smooth muscle cells. The rough-surfaced endoplasmic reticulum, however, is relatively prominent In some instances, the nuclear surface appears scalloped or folded, and the cell surface presents an irregular profile, similar to that of contracted cells.

South African platinum mine employees reduce smoking in 5 years.

BACKGROUND: South Africa adopted comprehensive tobacco control policies in the 1990s. Smoking has since declined in the general population, but there is little information on the effect of the campaign in labour-intensive industries, especially the mining industry where workers are exposed to dust, which may interact with tobacco smoke to cause respiratory disease. OBJECTIVES: To determine the prevalence of, and trends in, smoking in employees of a South African platinum mining company, from 1998 to 2002, and to describe some demographic factors associated with their smoking habits. METHODS: This study used smoking data collected during annual fitness-to-work medical examinations. Employees were categorised into never, ever, continuous, new and ex-smokers. Data were analysed by race and age group. Age-standardised smoking prevalence rates were compared with rates in the South African general population. RESULTS: There were 80,713 records of 25,274 mine employees for the 5-year period. The decrease in smoking prevalence over this period was significant in both black and white men, but was greater in the former (from 42.9% to 29.8%, and from 47.2% to 44.7%, respectively). In 2002, the prevalence of smoking in black mine employees was 12.1% lower than that in black men in the general population. The prevalence of smoking decreased in black mine employees in all age groups (p<0.001); no such trend was seen for white mine employees. The proportion of light smokers increased significantly from 59.9% to 64.7%, with a corresponding significant decrease in the proportion of moderate and heavy smokers from 28.0% to 25.4%, and from 12.1% to 9.8%, respectively. CONCLUSION: This study showed a significant decrease in smoking prevalence over a relatively short period, despite the fact that there was no smoking cessation programme in the company. The decline can be largely attributed to the South African government's antismoking initiative and supports the drive to continue to increase excise taxes on cigarette products. Nevertheless, the relatively high prevalence of smoking in some groups of mine employees highlights the need for workplaces to support the government's initiatives to curb smoking by establishing smoking cessation and prevention programmes.

Body weight, dietary practices, and tumor susceptibility in the rat.

The mature body weight of outbred CD-Crl:COBS CD(SD)BR male rats permitted to select their own diets throughout life was shown to correlate linearly with the frequency of spontaneous tumors. In an analysis of the dietary practices of these animals, a multifactorial model was derived--for which prepuberty and early post-puberty data only were used--that accounted for a large proportion of the variance in mature weight. The level of food or calorie intake proved less informative than the following: the interactive effects of food intake relative to body weight, the proportion of protein and carbohydrate constituents in the diet, the intake of each of these components, and, particularly, the efficiency with which the diet consumed was used for growth during early postweaning life. In a prospective study of other rats maintained on a similar feeding regimen, the model was found to be an accurate predictor of mature weight. Several of the explanatory factors necessary for estimation of body weight also contributed to tumor susceptibility. Nonetheless, both dietary and body weight-related factors in a specific time-related sequence were required to explain variation in spontaneous tumor susceptibility.

Dietary practices of early life and age at death of rats with tumors.

The association between the age at death of rats that develop spontaneous tumors and their early life dietary practices and growth responses was investigated. The data were obtained from outbred male Charles River CD Crl:COBS CD (SD)BR rats maintained for life on a self-selection dietary regimen that permitted them to regulate their protein intake apart from energy intake. A series of multivariable models was derived, after the rats were grouped by tumor type, that accurately accounted for the age of death of the individuals in each class. The models that explain the variance in death age of rats that develop tumors also differed from the combination of factors for rats that do not develop tumors but succumb to other age-related diseases. Although dietary protein and measures of growth are ubiquitous features in these models, no one set of idealized conditions for longevity can be proposed.

Contribution of body weight and growth to risk of anterior pituitary gland tumors of the rat.

The dietary and growth histories of noninbred male Charles River COBS rats permitted freedom of dietary choice throughout life were analyzed to determine the conditions associated with the spontaneous occurrence of anterior pituitary gland tumors (PT). The animals were allowed to regulate their protein intake apart from energy intake. Multivariable models were derived distinguishing rats that develop PT from those remaining free of tumors throughout life. Conventional fixed diet studies suggested that the quantity and quality of the diet consumed would be the best explanatory variables. However, body weight-related variables were found to be more important. The interacting, time-related conditions conductive to a high probability of PT occurrence included an unusually high growth rate associated with a high level of conversion of the food consumed into body mass during early life and a high intake of protein relative to body weight during early adult life. The accuracy in identifying rats with PT was even greater if mature body weight was included as an explanatory variable.

Sex differences in blood-oxygenation-level-dependent functional MRI with primary visual stimulation.

OBJECTIVE: The authors evaluated the effect of sex on data derived from activation studies using blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (MRI). METHOD: Gradient echo-echo planar imaging was used to measure BOLD signal response in the primary visual cortex in response to binocular photic stimulation in 16 healthy, young subjects (eight women and eight men). RESULTS: BOLD signal response was 38% lower in women than in men, and much of the difference was lateralized to the right hemisphere. CONCLUSIONS: Lower BOLD signal response in women may reflect a sex difference in the brain's response to a primary visual stimulation or in the physiology underlying BOLD functional MRI signal changes.

Dietary habits and the prediction of life span of rats: a prospective test.

A multivariable statistical model for predicting the duration of life of rats permitted to select their own diets was evaluated prospectively. With information relating to pre-adult dietary habits and growth responses, the predicted length of life for an individual closely matched the observed life span; the average absolute error was 11%. This suggests that, even under normal feeding conditions, the diet/growth history is an important factor bearing on death rate. In general, an early adult death age is associated with a high food intake prior to adulthood particularly when coupled with a high efficiency of food utilization during the post-puberty period, a rapid growth rate and early attainment of mature weight. Deviations from this pattern serve to increase the duration of life of the individual.

Down's syndrome: is there a decreased population of neurons?

Although gross abnormalities have been described in the brains of patients with Down's syndrome (DS), microscopic studies have revealed only minor and inconsistent findings. We compared two DS brains, in whole-brain serial sections, with similarly prepared age- and sex-matched normal controls. Architectonic abnormalities were noted, and cell counts revealed a significant poverty of granular cells in the DS brains, particularly in granular fields such as areas 3, 17, and 41. Golgi studies demonstrated all major cell types. A striking feature of the brain morphology in DS may be the curtailment of a specific cell type, most likely the aspinous stellate.

Root stimulation studies in the evaluation of patients with motor neuron disease.

Nerve root stimulation may be employed in patients with motor neuron disease (MND) to rule out motor neuropathy with conduction block. The diagnostic utility of these studies is unknown, in part because the range of amplitude changes across nerve root segments in patients with active neuronal degeneration has not been well studied. We reviewed root stimulation studies in 32 patients (59 nerves) with MND and found segmental amplitude reduction from 0 to 45%, a range similar to values reported for normal subjects; there was no suggestion of conduction block based on our usual criteria.

Age-related reduction in functional MRI response to photic stimulation.

Many functional imaging studies have demonstrated age-related alterations in cerebral blood flow during the resting state. However, few studies have addressed possible differences in functional response to cerebral activation. We assessed the response of visual cortex to photic stimulation in 9 normal elderly subjects and 17 normal younger subjects with blood oxygenation level dependent functional magnetic resonance imaging. We found that the amplitude of response in elderly subjects was significantly decreased compared to younger subjects (2.5 +/- 1.0% versus 4.0 +/- 1.6%, p = 0.01), suggesting a reduction in functional activation or an age-related alteration in the coupling of blood oxygenation to focal activation.

The effect of dosage cards on compliance with directly observed tuberculosis therapy in hospital.

We evaluated the effect of a dosage card signed by both patient and health worker on compliance in a tuberculosis ward. Compliance was assessed by testing a urine specimen from each patient for the presence of isoniazid and rifampicin pre-intervention and at two weeks, six weeks and 16 months post-intervention. Pre-intervention compliance was 62% and increased to 88%, 91% and 93% in the short, medium and long-term, respectively (P = 0.03, P = 0.02, P < 0.01). The assumption that directly observed therapy is successfully practised in hospital is not always correct. Simple inexpensive measures can improve compliance and have an impact on tuberculosis control.

T1 effects in sequential dynamic susceptibility contrast experiments.

Residual effects of an initial bolus of gadolinium contrast agent have been previously demonstrated in sequential dynamic susceptibility contrast MR experiments. While these residual effects quickly reach a saturation steady state, their etiology is uncertain, and they can lead to spurious estimates of hemodynamic parameters in activation experiments. The possible influence of T1 effects is now investigated with experiments in which T1 weighting is varied as well as with serial regional T1 measurements. Little evidence for significant residual T1 effects is found, suggesting instead that susceptibility effects underlie these observations. An initial saturation dose of contrast agent minimizes this effect.

Ultrastructural alterations in the adluminal testicular compartment in men with varicocele.

Testicular biopsies from 21 otherwise healthy men with diagnosed varicocele were processed for light and electron microscopy. Whereas germ cell morphology and tissue architecture of the basal testicular compartment appeared normal, cellular mophology and intercellular associations of the adluminal testicular compartment were variably altered. In affected tubules, spermatid nuclear and acrosomal morphology was abnormal and sloughing was evident. Spermatids were maloriented relative to Sertoli cells, and Sertoli-germ cell junctional complexes appeared to be structurally abnormal. Contradistinctly, Sertoli-Sertoli cell junctional complexes appeared unaffected. Results from this study indicate that testicular disruption in varicocele is a phenomenon of the adluminal compartment, that the Sertoli cell is, in fact, more sensitive to perturbation of the testicular environment than are germ cells, and that the Sertoli cell is the primary intratubular site of alteration leading secondarily to spermatogenic disruption.

Disk drusen and angioid streaks in pseudoxanthoma elasticum.

Visual field loss secondary to optic disk drusen became evident before the development of angioid streaks in a patient with pseudoxanthoma elasticum. The incidence of optic disk drusen in cases of pseudoxanthoma elasticum is 20 to 50 times greater than that in the healthy population. We postulate that the abnormal aggregation of macromolecules with a high affinity for calcium (resulting in abnormalities in elastin in cases of pseudoxanthoma elasticum) also develops at the cribriform plate, disrupting axonal flow and leading to disk drusen formation. Pseudoxanthoma elasticum is associated with marked cardiovascular and gastrointestinal morbidity. Moreover, macular hemorrhage and precipitation of angioid streaks have frequently been noted after trauma. Prompt diagnosis of pseudoxanthoma elasticum will allow necessary prophylaxis and must be considered in patients with optic disk drusen.

Viral hepatitis in South African healthcare workers at increased risk of occupational exposure to blood-borne viruses.

The prevalence of hepatitis A, B and C antibodies was measured in a group of healthcare workers (HCWs) at increased risk of occupational acquisition of blood-borne viruses (N=402) from a large, urban referral hospital in South Africa. The aims of this study were to determine the immunity of HCWs to these agents and to recommend policy for the protection of HCWs against occupational exposure to viral hepatitis in this country. Race, sex and age were shown to be important factors influencing the presence of hepatitis A (HAV) antibodies. Most black HCWs (96.2%) are protected from HAV infection. Females have significantly higher HAV antibodies compared with males and antibodies increase with increasing age. Hepatitis B antibodies (anti-HBs) were found in 30.6% of HCWs. Anti-HBs levels were significantly associated with a past history of HBV vaccination. However, only a small proportion of HCWs (21.2%) could remember ever being immunized against HBV. For those individuals that did receive HBV vaccination (N=83), the mean number of years since their last vaccine was 6.2 years (SD +/- 3.5). HCV antibodies were found in 1.8% of HCWs at increased risk of occupational exposure. It was not possible to define whether these infections were occupationally acquired but genotyping of the HCV (in two of seven cases) showed genotype 5, the predominant South African genotype. New recommendations for the prevention of viral hepatitis in HCWs in South Africa are made, including pre-employment screening for HAV based on self-selection criteria, universal anti-HBs screening with HBV booster vaccination. HCV recommendations are based on appropriate education of HCWs about this infection and its prevention and a standardized post-exposure testing protocol.

Apparatus for evaluating vapor-induced dispersal of Blattella germanica (Dictyoptera: Blattellidae).

An apparatus for evaluating vapor-induced dispersal of Blattella germanica (L) is described. It is made of two 750-ml crystallizing dishes connected by a glass and wire mesh tube. Its use is illustrated by experiments on exposure of late instars to vapors of a propoxur in oil formulation and those of its solvent system.

Reduction in BOLD fMRI response to primary visual stimulation following alcohol ingestion.

The physiology of alcohol's effects on brain function is poorly understood. Emission tomographic imaging has revealed both acute and chronic alterations in resting cerebral hemodynamics and metabolism following alcohol ingestion. However, cerebral functional integrity under these conditions has received less attention. Functional magnetic resonance imaging (fMRI) offers a non-invasive method for assessing brain functional activation. In order to assess its utility for studying the effect of alcohol on brain function, we performed fMRI with photic stimulation before and after administration of either 0.7 mg/kg alcohol (N = 12) or placebo (N = 5), resulting in peak breath alcohol levels averaging 0.069 g/dl. We found that the amplitude of visual cortical activation in response to photic stimulation was significantly reduced by approximately 33% following alcohol administration (4.0 +/- 1.7% vs. 2.7 +/- 1.3%, P = 0.02), but not following placebo (4.2 +/- 1.5% vs. 4.1 +/- 1.4%, P = 0.7). The results also suggest that the baseline right hemispheric predominance of activation in response to photic stimulation may be reduced following alcohol, suggesting a greater effect on the right hemisphere, consistent with previous studies and alcohol's known effects on visuospatial processing. In addition, through the course of each activation session, there was a progressive reduction in response following alcohol. These data demonstrate that the cerebral effects of alcohol intoxication can be studied with fMRI, and that the effects on brain function of even moderate alcohol intoxication may be widespread, may be lateralized, and may include the visual system.

Influence of baseline hematocrit and hemodilution on BOLD fMRI activation.

Current understanding of blood oxygenation level dependent (BOLD) fMRI physiology predicts a close relationship between BOLD signal and blood hematocrit level. However, neither this relationship nor its effect on BOLD percent activation (BPA) has been empirically examined in man. To that end, BPA in primary visual cortex in response to photic stimulation was determined in a group of 24 normal subjects. A positive linear relationship between BPA and hematocrit was seen, particularly in men. To evaluate the effect of change in hematocrit on BPA, 9 men were studied before and following isotonic saline hemodilution, resulting in an average 6% reduction in hematocrit and an 8-31% reduction in BPA. No significant change in the number of activated pixels was seen. A model of predicted BPA as a function of hematocrit and vessel size was developed, and results from this model closely mirrored the empiric data. These results suggest that hematocrit significantly influences the magnitude of BPA and that such baseline factors should be accounted for when comparing BOLD data across groups of subjects, particularly in the many instances in which hematocrit may vary systematically. Such instances include several disease states as well as studies involving sex differences, drug administration, stress and other factors. Finally, the robust agreement between predicted and empiric data serves to validate a semiquantitative approach to the analysis of BOLD fMRI data.