Further observations on hydrogen peroxide antisepsis and COVID-19 cases among healthcare workers and inpatients.

BACKGROUND: The use of prophylactic antisepsis to protect against coronavirus disease 2019 (COVID-19) has been suggested. This study investigated hydrogen peroxide antisepsis (HPA) at two hospitals in Ghana. METHODS: Cases of COVID-19 among healthcare workers (HCWs) using hydrogen peroxide (HP-HCWs) or not using hydrogen peroxide (NHP-HCWs), vaccinated or unvaccinated, were recorded at Shai-Osudoku Hospital (SODH), Dodowa, and Mount Olives Hospital (MOH), Techiman, between May 2020 and December 2021. The effect of HPA in all inpatients at MOH was also observed. Permutation tests were used to determine P values. FINDINGS: At SODH, there were 62 (13.5%) cases of COVID-19 among 458 NHP-HCWs but no cases among eight HP-HCWs (P=0.622) from May to December 2020. Between January and March 2021, 10 (2.7%) of 372 NHP-HCWs had COVID-19, but there were no cases among 94 HP-HCWs (P=0.206). At MOH, prior to HPA, 17 (20.2%) of 84 HCWs and five (1.4%) of 370 inpatients had COVID-19 in July 2020. From August 2020 to March 2021, two of 54 (3.7%) HCWs who stopped HPA had COVID-19; none of 32 NHP-HCWs contracted COVID-19. At SODH, none of 23 unvaccinated HP-HCWs and 35 (64%) of 55 unvaccinated NHP-HCWs had COVID-19 from April to December 2021 (P<0.0001). None of 34 vaccinated HP-HCWs and 53 (13.6%) of 390 vaccinated NHP-HCWs had COVID-19 (P=0.015). No inpatients on prophylactic HPA (total 7736) contracted COVID-19. CONCLUSION: Regular, daily HPA protects HCWs from COVID-19, and curtails nosocomial spread of SARS-CoV-2.

Morphometric study of specific heart granules in the grey seal (Halichoerus grypus).

Specific heart granules in the grey seal, Halichoerus grypus, a marine mammal, were studied and compared with those in the Wistar rat by ultrastructural morphometry. There is extreme paucity of these granules in atrial cells of the seal, even in the region of the Golgi apparatus, compared with those in the rat. By numerical concentration, granules in the seal are 23 times fewer in number than in the rat. They are also fewer in number than in bats and hamsters for which data is available. The mean (+/-SEM) diameter of heart granules in the seal is significantly less (188 +/- 5.3 nm) than that of the rat (226 +/- 4.6 nm). These observations, the first in a marine mammal, are of interest in relation to the need for conservation of water and electrolytes in pennipids.

Ultrastructural and morphometric features of nodal and impulse-conducting cardiac myocytes of the bat Pipistrellus pipistrellus.

Cells of the impulse-generating and conducting tissues of the insect-eating bat Pipistrellus pipistrellus were studied and evaluated using ultrastructural morphometry. Sinoatrial node cells are smaller than working atrial cells and measure about 6.5 microm in diameter. Their mitochondira and myofibril content constitute 23% and 19% of cytoplasmic volume, respectively. Corresponding values for working atrial cells are 23% and 52%. Atrioventricular node cells are 4.2 microm in diameter and contain abundant glycogen in the cytoplasm. The fractional volume of mitochondria in about 24% while that of myofibrils is 7%. Cells of the bundle of His are larger (6-8 microm diameter) and contain more cellular organelles than do nodal cells. Their mitochondria and myofibril contents are 25% and 25%, respectively. Cells in the proximal part of the right bundle branch are slender with diameters averaging 3.4 microm. Mitochondrial content is 23% while myofibrils occupy 20% of the cytoplasmic volume of these cells. Distally located bundle branch cells measure 7-10 microm in diameter with mitochondria and myofibril volumes of 30% and 33%. Subendocardial cells in the ventricular free wall are large reaching 28 microm in diameter (cf. 14-18 microm in working ventricular cells) and have mitochondira and myofibril volume fractions of 32% and 29%, respectively (35% & 40% for working ventricular cells).

Ultrastructural characteristics of atrial, ventricular and subendocardial (Purkinje) cells of the fruit-eating bat Eidolon helvum.

The ultrastructure of the myocardium of the large (285 gm) fruit-eating bat (Eidolon helvum) provides further evidence that, among mammalian species, different types of cardiac myocytes are morphologically heterogeneous. Atrial cells of this species, like those of smaller bats previously studied, have few of the natriuretic hormone-containing granules. These granules are also small, with a mean diameter of 176 +/- 3.9 nm, in comparison with those of the rat (230 +/- 5.8 nm) and mouse (211 +/- 4.7 nm). In all types of myocytes of the bat investigated, mitochondrial matrix granules are more prominent than in those of the rat and mouse. Also distinctive are the Purkinje cells which, aside from their large size (30 microns) and lack of T-tubules, have atrial granule-like inclusions. These cells are well endowed with mitochondria (28% of cytoplasmic volume) and with lipid bodies but have few glycogen granules. Their myofibrillae (33%) are well aligned. The ventricular cells (average diameter 14 microns) have nearly equal volumes of mitochondria (41%) and myofibrils (47%). Mitochondrial cristae, however, are not compactly organized. Lipid material is found in the matrix of the mitochondria. Extensive evaginations of endothelial cells of the bat endocardium appear continuous with endothelial vacuoles. In these endothelial cells, there are also many dense granules of varying shapes and sizes.

Comparative ultrastructural morphometric analysis of atrial specific granules in the bat, mouse, and rat.

Size, incidence, and volume density of atrial specific granules (ASG) in right atrial cells from five animals each of the rat (average weight 210 g), mouse (average weight 28 g), fruit-eating bat Megaloglossus woermanni (BMW; average weight 35 g), and the insect-eating bat Pipistrellus pipistrellus (BPP; average weight 6 g) have been compared via ultrastructural morphometry. In all three parameters of granule measurement, significantly higher figures were obtained in the rodents than in the bats. However, between the rat and the mouse, as also between the two species of bats, no significant differences were noted in any of the measurements. These results therefore do not support the prevalent view that the number and size of the granules decrease with increase in size of the animal species. The low content of ASG in atrial cells of the bats is probably an indication of low demand for the natriuretic hormone of the granule, because, in such animals, and particularly in flight, conservation of fluid and electrolytes is of paramount importance. This suggests that granule content is adapted to fluid and electrolyte regulation in relation to the functional capacity of the animal. We also observed ASG-like structures in endothelial cells of capillaries of bat tissue but not in rodents. The function of these granules or whether or not they represent atrial specific ones is not clear from the present study.

Morphometric study of ventricular myocardial cells in the bat (Pipistrellus pipistrellus), hamster (Mesocricetus auratus) and Wistar rat.

A comparative morphometric study of ventricular myocardial cells of the West African insect-eating the Pipistrellus pipistrellus, the hamster and the rat revealed significant differences in volume fractions of mitochondria myofibrils, lipid bodies and T tubules. In the cells of the bat, mitochondria constitute 35% of cytoplasmic volume compared with 29 and 30% in the hamster and rat, respectively. Notably, crista density is much higher in the bat cells (3.58 x 10(5) cm-1) than in those of the hamster (2.59 x 10(5) cm-1) and of the rat (2.48 x 10(5) cm-1). Myofibril concentration is 40% in the bat, 53% in the hamster and 55% in the rat. There is greater numerical density of lipid bodies in the bat (212.27 x 10(9) cm-3) than in the hamster (139.20 x 10(9) cm-3) and in the rat (114.00 x 10(9) cm-3). The volume occupied by T tubules is 0.02 in the bat and hamster, and 0.009 in the rat. These differences suggest structural design for efficient metabolic activity in the bat which, among mammals, has high exercise tolerance.

Fine structure of subendocardial (Purkinje) cells of the insect-eating bat (Pipistrellus pipistrellus).

Subendocardial cells of the right ventricular myocardium of the West African bat, Pipistrellus pipistrellus, were investigated at the ultrastructural level. The prominent features of these cells include a well-developed T-tubule system and numerous mitochondria with closely packed cristae. Additionally, the cells display large stores of lipid bodies. These unusual features confirm that Purkinje cells are heterogeneous in structural detail. From the paucity and poor structure of myofibrils of these cells, it is likely that the T-tubules may have a primary nutritional role in the regulation of electrolytes in an animal in which the cardiac cycle is particularly rapid. The well-developed mitochondria and the large stores of lipid bodies are appropriate for such active cells in which metabolism is probably of the aerobic type.

Ultrastructure of the internodal myocardium in the rat.

Ultrastructural studies of the rat atrial myocardium reveal that the specialised myocardial cells can be distinguished from the usual atrial myocytes by their lack of specific atrial granules. On the basis of this distinction it has been shown that there is interposition of atrial myocardial tissue in the pathway between the two nodes and that there are no morphologically specialised internodal pathways. The atrial myocardial cells themselves exhibit variations in their content of cytoplasmic organelles such as myofibrils, T-tubules and sarcoplasmic reticulum but they all contain membrane-bound specific atrial granules.

Ultrastructure of the ventricular myocardium of the bat Eidolon helvum.

Ultrastructural studies, including a preliminary morphometric analysis, of the right ventricular myocardium in the West African bat Eidolon helvum show that the myocytes contain a wider T-tubule system and a higher proportion of mitochondria and lipid droplets than in typical terrestrial mammals such as the rat; these features in the bat are even mor pronounced than in hibernating species such as the golden hamster. In addition to having coupling arrangements with T-tubules and surface sarcolemma, cisterns of junctional sarcoplasmic reticulum are closely apposed to mitochondria and lipid droplets.

The ultrastructure of myocardial cells in the golden hamster Cricetus auratus.

Electron microscope studies of the myocardium of the golden hamster revealed that the primary T-tubules in ventricular and atrial myocytes are substantially wider than their counterparts in most other mammalian species. Another feature is the presence of numerous lipid bodies but these are not as closely apposed to mitochondria as in seal myocardial cells. General atrial myocardial cells in the hamster contain numerous electron-dense spherical granules but these are absent from cells of the nodal and conducting system; in regard to these latter features in hamster resembles most other mammals.

The T-tubule system in the specialized and general myocardium of the rat.

The T-tubule system in cardiac muscle cells has been investigated with the electron microscope in 10 adult rats after infiltration with horseradish peroxidase. All cardiac muscle cells possess a T-system, but its complexity varies according to the region of the heart. It is most extensive in the general ventricular myocardium where there are primary, secondary and tertiary transverse tubules as well as longitudinal elements, and there are numerous couplings between the T-system and the sarcoplasmic reticulum (SR). The T-system and associated SR couplings are less extensive in the atrium and in the atrioventricular conducting system. It is least well developed in the nodes, particularly in the sinuatrial node, where it is restricted to primary T-tubules. There are numerous SR couplings with the sarcolemma in all types of cardiac muscle cells. Where intercalated discs occur, SR couplings are associated with non-specialized parts of the disc. The possible significance of these ultrastructural features in regard to the speed of conduction by myocardial tissues, and in the excitation-contraction sequence is discussed.